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Funny story - after all of this I was poking around on mine while putting a new battery in (the cold spree here finally killed the 5 year old battery in mine that's been in since I bought the car) and noticed I too was missing the ground from the back of the head to the firewall. I could have sworn I put one in... Turns out, not so much! Made a quick one and threw it on. Not sure if I'll notice any difference but it certainly can't hurt!
Whoa! So all this time you had the same ground missing but never had any apparent electrical issue with your GTE swapped SC. It's so weird how different cars can manifest grounding issues and some will not but I assumed at this point that the head ground being missing was a major thing for all SC's. Anyway I am glad you got it sorted out, Rudy! I still recall that your larger troubles have been with your 2JZ-GTE VVT-i ECU requiring the very proprietary GTE VVT-i throttle body. Hopefully NO more of that!!
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Since adding the direct cylinder head ground wire and the additional one to the rear side of the intake manifold my SC has been doing fine so far. I do think, however, that with the three auxiliary electric cooling fans, A/C, headlights, turn signals and brake lights all activated simultaneously I still do need some manner of alternator upgrade. With less of those functions on at the same time my voltmeter does read about 13.0-13.1V but with the headlights on at night while using brakes and turn signals with the engine at full operating temperature and the fans on I get occasional dips to 12.5V or less (briefly... when the turn signals are on).
After talking with Aaron at Driftmotion I am going to get my DC Power alternator tested locally at an Autozone and if it checks out OK I am going to reinstall it and see if its voltmeter is indeed stable. Aaron said that the missing cylinder head ground could potentially have thrown off the voltmeter in the DC Power alternator.
I'm not 100% sure on that since I have seen a few videos online of people with other DC Power alternators complaining of voltage regulator issues (which DC Power did fix for them with a replacement unit) but I will give it one more go with the DCP alt since I never tested it before correcting my ground issues.
I alternatively I have my eye on an OEM 2003-2010 Lexus SC430 6-phase 130 Amp alternator which has the factory oval connector built in.
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Also, thanks to some amazing info from Stu Hagen, Supralover93 and Beezupra on SF in the thread links below I think I finally have the confidence to move forward with replacing my stock CT12B twin turbos with the new set soon:
haha Craig! Here I was, giving out advice, when I needed to take my own! So far so good on this end. I do agree - it's funny how some of these cars react differently to various scenarios. I have started to notice the HID kit on my car (it's been on since I bought it years ago) does seem to draw a lot of power when I flick them on. Those may need to go this year...
I'll be curious about your alternator situation. Also - I absolutely can't wait to hear about the turbo replacement. A part of me is considering sending mine in for the overhaul/upgrade service as well. However, that's a dream for another time at this point!
haha Craig! Here I was, giving out advice, when I needed to take my own! So far so good on this end. I do agree - it's funny how some of these cars react differently to various scenarios. I have started to notice the HID kit on my car (it's been on since I bought it years ago) does seem to draw a lot of power when I flick them on. Those may need to go this year...
I'll be curious about your alternator situation. Also - I absolutely can't wait to hear about the turbo replacement. A part of me is considering sending mine in for the overhaul/upgrade service as well. However, that's a dream for another time at this point!
It's definitely weird if you did not have that cylinder head ground all this time and had no issues while I didn't and had the igniter burn out every so often. Although... I did get away with it for one whole year at longest record without that head ground before finally realizing it was missing and correcting it. Depending on how much you do or don't drive your SC300 it might have snuck up on you eventually. No way to tell when really. I can only speak from my own experience. I also do not know for sure whether or not one or more of my Denso ignition coils had an internal short in a secondary winding (which in the absence of that ground *might* possibly happen at high rpms...) but I replaced all six with new ones anyway.
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Both Ali and Lexus2000 have stated that they prefer LED upgrades for the headlights over HID kits and what you have described is exactly what any HID ballast does at cold startup: each ballast can draw up to 20 Amps give or take for a second or two right when the bulbs are first turned on and begin to heat up. Once the bulbs come up to temperature the current draw usually stabilizes and holds at 3.5-4 Amps.
I am not sure what issues this can really cause to the rest of the car's electrical system but what I did recently when re-designing all my add-on electrical circuits was to gauge each wire for the distance to the mini fuse box with the left and right ballasts appropriately and give each of them a 20A fuse. So far my Phillips ballasts do not blow those fuses on cold startup. My XenonDepot HID kit's original wiring specified 30A fuses but that's a LOT of overkill for what each ballast actually draw I think (should be closer to 17-18A at cold startup for the 1-2 seconds before coming down to settle at 3.5A or so).
I've never noticed any issues with my HID system but I'm very picky about the brand that I use and trust.
I have been looking into LED 9006 headlight kits and the same for the high beams. I may try LED's with the high beams first to see how it goes.
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I haven't yet had a chance to test the DCP alternator before installing it but as soon as I have some results I'll post them up. The stock Supra TT Auto alternator is holding fine for now other than that I can clearly tell that running every system at once is taxing it a bit.
I can't wait to finally get into the turbo replacement myself! I have made a list of all the extra tools that I will need for the job and I am seeking all of those out at this time. Then I need to buy any of the recommended replacement OEM nuts that the TSRM "hints" at
If you are considering getting your turbos replaced I highly recommend "The Boost Lab" of Tampa Florida. While I have not yet run their rebuilt turbos I was very impressed with them. They probably will work on the CT20B's in your VVT-i engine. You're probably thinking of doing the STU Hybrid upgrade though. I know a few shops offer that service on the JDM twins. I believe that Stu Hagen himself also can be contacted for this purpose as well but I'm not 100% on that.
If you are considering this I recommend you check out some recent posts in the big Hybrid stock twin thread on SF made by Beezupra where he details some upgraded water cooling lines that he has had made which can better withstand the extra heat generated by the hybrid turbos.
LED's are great. I ran them on my daily driver for a while. Or until it got cold and started snowing. Because the LED's dont produce heat at the front of the bulb the headlight glasses started to freeze and collected all the snow and ice on them until they were completely covered and undriveable at night. And because they usually have a heatsink at the back of the bulb they do not fit into the stock headlight housing and some modification is necessary to keep the dust out.
Depending on the local weather conditions, it could be a problem.
LED's are great. I ran them on my daily driver for a while. Or until it got cold and started snowing. Because the LED's dont produce heat at the front of the bulb the headlight glasses started to freeze and collected all the snow and ice on them until they were completely covered and undriveable at night. And because they usually have a heatsink at the back of the bulb they do not fit into the stock headlight housing and some modification is necessary to keep the dust out.
Depending on the local weather conditions, it could be a problem.
I had not considered that problem . I'm probably not going to take my SC through any snow (mostly to avoid road salts) but the lack of much heat from an LED allowing old conventional headlight lenses to freeze over sounds like an issue I want to avoid if I ever did. I have also noticed the wide variance in 9006 LED bulb designs at the front elements and rear behind the twist-in locking tabs. Some look like they would fit better than others.
I won't modify my factory housings in any way to fit one of these bulbs though. The HIDs twist right in like a conventional bulb and clear everything at the back. The only LED bulbs that I'll use will have to offer the same level of ease.
I have been running LED lights in my SC for over a year and recently installed a set in my wife's Murano. They are two different brands and we are both very happy with the night vision especially at our age. Neither brand required any modification to the housings at all. Living here on the Gulf Coast we have not seen snow in a number of years so that is not anything for us to worry about. I will add this recent big storm that came across Texas brought snow north of us. God luck.
Bill
It seems my post was slightly misleading. The SC headlights do not require modification. My daily driver is a Jaguar that has H1 bulbs and they have a screw on cap at the back that fowls on the LED heatsink. And on that application the modifications were necessary.
I got it bench tested at a local Autozone. Apparently they have no printout for this service but on the computer's screen the unit checked out and its voltage regulator was fine... for the short time that it runs its test cycle.
Last night I took out the OEM Supra TT Auto alternator, installed the DC Power alternator again and reinstalled the 2/0 alternator to battery positive cable with its 200A in line fuse.
As before with this alternator everything was fine at cold startup for the first few seconds. Then after about 20-30 seconds the voltmeter needle started jumping around again in exactly the same way as before. I then shut the engine down myself before the ECU might have started freaking out, pulled the DCP alt and reinstalled the OEM Toyota alt.
This confirms for me that the DC Power alternator's voltage regulator was indeed defective in the first place. It was not due to the cylinder head ground being missing and it was not due to the unrelated loose accessory belt and bad accessory belt tensioner (which were all fixed). I'll call their tech support this coming week and see about sending it in to them for a replacement.
However...
Regardless of a warranty repair or replacement I will instead go with this OEM 2003-2010 SC430 (and 2000-2003 LS430) alternator upgrade. P/N: 27060-50280. They are 6-phase and rated 130 Amps which should be all I need with a factory quality design that has far better idle amperage output.
It's the same thing as the popular Tundra and Sequoia alternator only with a compatible oval plug. I'll just have to modify the front casing by cutting off one mounting ear and evenly trimming back a few millimeters of material at the back of the top ear (although IF it happens that the DC Power alt's front custom machined casing is a bolt-on swap... which is only my wishful thinking at this point... then I'll try that first).
Don't get me wrong... the DC Power alternator is said to be very high quality and does look like it and I am sure the company can make this right with a replacement unit but having an issue like this right out of the box has made me turn to a modified-OEM solution.
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I'm also still seeking out quality LED bulbs to bring the power draw of the turn signals and tail lights down considerably but I haven't found any quality ones yet that aren't $50 each. I have to keep looking (and just FYI to anyone who hasn't seen earlier posts this does involve using a custom flasher relay by Lexus2000 and disabling the tail light failure ECU's warning light circuit).
For the most part the 100A Supra TT Auto alternator does just fine. It's just the turn signals, brake lights and additional 18 Amps of draw from all three electric fans that tends to strain the factory alternator's ability to keep up. When the signals are being used and/or brake lights at the same time I can dip down to 12.5V on the voltmeter momentarily on each blink. When the brake lights are off and with the turn signals not being activated the stable voltage rests at 13.0-13.1V *with* the three electric fans, A/C and HID headlights on.
So in all the current draw is usually OK... until I start activating signals or brake lights with all of the constant load. I have no issues electrically while driving but seeing the voltmeter dip just barely below 12.6V with all of that current draw tells me I still need a 6-phase alternator upgrade. The TT Auto alternator is very close to being enough... but it's not quite enough.
I'm also still seeking out quality LED bulbs to bring the power draw of the turn signals and tail lights down considerably but I haven't found any quality ones yet that aren't $50 each. I have to keep looking (and just FYI to anyone who hasn't seen earlier posts this does involve using a custom flasher relay by Lexus2000 and disabling the tail light failure ECU's warning light circuit).
When it comes to reliability LED bulbs are various levels of suck. I've bought cheap ones, high end ones had failures with all of them. I just accept it at this point. For the rears you have so many choices depends how bright you want the bulbs to be. These are GREAT when it comes to light scatter/diffusion just as good as the incandescent and are about the same brightness. https://www.ebay.com/itm/262842610872
Downside is they are yellow not amber/orange but it might not matter when going through the amber lens of the tail light. Upside is they run cool and are cheap. I have run a set for about 2 years still going I would have been happy if they lasted a year. IMO that is your best solution if you're happy with a stock level of brightness.
3 of them will mean your signals are very bright. For the fronts I can't recommend any 1157 LED bulb none of them have a big enough difference between low and high. Most are 2-3x it needs to be 6x or more 8-10x is great. If there is such an 1157 LED bulb I'd like to know about it. Or you can use an 1157 LED with a buck converter like this
I've experimented with them most LED bulbs will dim down a fair bit so with a little bit of rewiring you can get the proper low/high effect.
So in all the current draw is usually OK... until I start activating signals or brake lights with all of the constant load. I have no issues electrically while driving but seeing the voltmeter dip just barely below 12.6V with all of that current draw tells me I still need a 6-phase alternator upgrade. The TT Auto alternator is very close to being enough... but it's not quite enough.
Once you get rid of all the halogen/incandescent bulbs you should have more than enough reserve. Especially if you go LED on the headlights.
......on LEDs for headlights on a budget these are best
I LOVE the LED bulbs on my SC. It's really hit or miss on each car if the housing will work well for them and i can confirm the SC is great. I had them on my 04 silverado too and they were awful on that haha.
When i turn the brights on in the SC its the same or brighter than my 2018 Audi with its fancy lighting.
Looks like I need a new fan controller... or two fan controllers :D
I keep saying I’m going to get to replacing my old turbos soon and I really was getting ready to this time after dealing with many other recent non-car projects... but of course fun things happen first.
Tonight I noticed that my auxiliary fans weren’t coming on when they should while the A/C override trigger was activated.
I pulled it up on its harness and wiggled its wires a bit. That’s when I noticed this:
That’s my Mishimoto fan controller. It’s a ground-switching type unit with a maximum continuous current rating of 25 amps.
According to the Supra TT TSRM the two pancake helper fans behind the radiator draw about 5 amps each and the large conventional motor fan in front of the condenser draws 8.5 amps. That’s about 19 continuous amps combined and well under the limit.
Yet as you can see here the thick black ground wire from the Mishimoto controller must be heating up quite a lot as the plastic of the Molex style connector is beginning to melt and deform. Yikes!
All my other wires in these circuits and the fuses and relays appear to be fine. It’s just this area of the Mishimoto controller that is showing signs of current overloading one part of it.
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I bought this controller in 2018 and never saw a melted connector condition until now, after I added the two extra OEM Supra TT fans to its circuit.
Either it actually has less max current capability than 25A or the three fans together actually draw more than 19A.
It also is not weatherproofed by Mishimoto and has NO rubber seals at the connector wire terminals coming from it. I’ve also got it sitting close to the side of my aluminum radiator in front of the battery... but it has always been totally dry in that location.
Some corrosion from the air was able to form at the exposed metal of the Mishimotor wire terminal ends and on the spades of the connector that go into the module.
I think hot glue weather sealing will be a requirement for a new one since there are no gaskets included.
Or perhaps a ton of dielectric grease?
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For now I have disconnected the third fan on the A/C condenser. Glad I went to the trouble of adding in a handy service disconnect for each individual fan! I’ve put electrical tape over these connections for now.
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I’ve also ordered another identical Mishimoto fan controller to replace the old one.
For now until I can work out a permanent solution I’m going to run on just the main clutch fan and twin pancake auxiliary fans. The Mishimoto will handle the load from just those.
I’ll have to see how much of that black wire needs replacing into the rest of my harness. I’ll check it carefully for any insulation cracks or melts.
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Long term, I guess I either need a beefier aftermarket fan controller... or two Mishimoto fan controllers (one for the rad aux fans and one for the condenser fan) triggered by the same coolant sensor and A/C clutch wires... or maybe I need to install a Supra TT style two-way A/C pressure switch and the TT lower radiator temperature switch to 100% recreate Toyota’s OEM control system for these three fans.
The latter solution is becoming more appealing now to be honest but I’ll need to identify a couple more parts to do that.
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As far as I can tell though the rest of my recent circuit rewiring job with extra relays are all fine with no issues. My wire size choices seem to be okay otherwise.
I think either the three fans together pull more amps than they are said to pull... or just the old used condenser fan pulls more than 8.5A... or the Mishimoto controller in truth maxes out closer to 18-20A rather than the official 25A rating.
No fuses blew on any circuits and I have properly rated fuses and appropriate wires connected to all those fuses.
The problem seems to be localized right at the fan controller only.
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At least I can probably run on just the mechanical + two rad cooling fans only for the moment!
The replacement identical fan controller arrives in a couple of days.
Kahn - good catch before summer time! Get that baby tidied up so that you can hurry up and get those turbos in (or, I guess, you can send em my way and I can break them in for you).
Kahn - good catch before summer time! Get that baby tidied up so that you can hurry up and get those turbos in (or, I guess, you can send em my way and I can break them in for you).
Haha! I guess your stock twin 2JZGTE could use a turbine upgrade if you want to change all the piping along with them! Actually from what I understand the 2JZGTE VVT-i turbochargers went to steel exhaust wheels just like the Export CT12B's. The shafts in between the blades are also supposed to be beefier than on the CT12B's and that's among the reasons that the STU Hybrid upgrade is much cheaper for CT20 stock twin donors than it is for my version of the stock twins.
I'm definitely getting to them soon for real this time, lol. It's just been one thing after another lately taking priority over that big job (and bad weather days) since the SC has been otherwise fine to drive carefully. But it's time now.
As for the fan controller issue-- yeah I am certainly glad I caught the electrical overload before it became a potentially larger issue. None of my other wiring seems to have been at fault. It's just the controller with its rather small ground wire for a claimed 25 Amp continuous rating. Maybe Mishimoto expects the ground wire distance to be REALLY short. No idea but for whatever reason three OEM fans rated at 19A combined seem to have overwhelmed at least that wire and the connector.
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I received the replacement controller yesterday and after getting a call from a friend who's in town for an impromptu socially distanced meetup I scrambled to install it and correct the wiring but I need another afternoon with it to finish. This is after disconnecting the Soarer A/C condenser fan temporarily.
In the longer term I think I will remove the Mishimoto controller entirely and recreate Toyota's Supra TT fan relay temp and A/C pressure switch setup.
Especially since I inspected the SC's A/C pressure switch and found that it is apparently the SAME pressure switch that all the Supra MKIV TT's have! There are already four pins there but only two of them are used. And the connector for the A/C pressure sensor on the SC, 90980-10943, is exactly the same as the one listed for the MKIV TT. It's just missing two terminal wires that would form part of the fan relay circuit's trigger.
So in reality all I need to do is buy one weather proof heavy duty relay and make a bracket for it to install somewhere behind or under the driver's side headlight, buy two more OEM terminal wires for the A/C pressure switch that came with my SC and install the Supra TT radiator temp switch that completes that fan relay trigger path. And I already happen to have one of those too along with its connector and terminals. That means there's no need to discharge and recharge the A/C system to change to another pressure switch to get that function working on the A/C side : )
That four-pin A/C pressure switch seems to have been standard on ALL SC's from 92-00. Seems they also came on all MKIV's. It's just that on SC's and non-turbo MKIV's only two of the pins were used rather than all four for Supra TT's (and Soarer 1JZ-GTE's).
This is good information for anyone who may want to replicate the stock Supra TT fan control trigger setup... if they're up for the rest of the relay wiring work that will go with it.
This car keeps revealing conveniently awesome little secrets!
I'm not doing that electrical job just yet but when I do I will post the TSRM electrical schematics and notes for its wiring path. It seemed daunting to put together when I first wired the car because I was completely unaware that the "special" A/C pressure switch that I needed was there all along!
I've heard that my turbos came with steel wheels, I've also heard guys swear they pulled them apart and found ceramics... It's so hard to know for sure without pulling mine! I'm genuinely curious... However, they're holding up great at this time and I'm trying to leave the stock twins and enjoy them for as long as I can (or until I stumble across a single kit that I can't say no to lol).
Can't wait to hear about you installing them - hope it goes smoothly. I also enjoy your thoroughness as always with your electrical diag and repair! You're much more patient than I am in that way.
Now I'm curious as well! I thought all the 2JZ-GTE VVT-i engines went away from the ceramic turbo exhaust wheels. Maybe that was only true for those GTE VVT-i engines found in JDM Supra TT's...? I had thought it was true of all the 2JZ-GTE VVT-i engines regardless of the vehicle they originally came with.
I think it will go smoothly at this point. I just need a good weather week soon to get started and dive in. If the mosquitoes would lay off that would be great too! It's not that I'm patient about it. I just have had thing after thing and bad weather keep getting in the way of actually doing it. I'm so beyond over having to short shift at 3800RPM or even at 3500RPM if I'm too aggressive on the throttle.
The current electrical fix is just annoying because the fan control wiring was already completed and supposedly rated for more current and should be drawn! But I do want all three auxiliary fans to run reliably to keep the engine as cool as possible on hot days so whatever it takes to achieve that. The Mishimoto controller has been replaced with a new one and the offending melted connector and older wiring for it has been replaced. The un-insulated connector holes exposing the terminals to air have been insulated with hot glue. Interestingly it was ONLY the terminals at that connector that had corrosion.
For now I'm leaving the OEM A/C condenser fan disconnected until I revise the whole control circuit Toyota's way. I just needed it temporarily fixed quickly for now.
02-15-21, 10:20 PM
. I'm probably not going to take my SC through any snow (mostly to avoid road salts) but the lack of much heat from an LED allowing old conventional headlight lenses to freeze over sounds like an issue I want to avoid if I ever did. I have also noticed the wide variance in 9006 LED bulb designs at the front elements and rear behind the twist-in locking tabs. Some look like they would fit better than others. 
Actually from what I understand the 2JZGTE VVT-i turbochargers went to steel exhaust wheels just like the Export CT12B's. The shafts in between the blades are also supposed to be beefier than on the CT12B's and that's among the reasons that the STU Hybrid upgrade is much cheaper for CT20 stock twin donors than it is for my version of the stock twins.
