Parasitic draw coming from AC fuse. What's the next step?
07-05-22, 06:53 PM
#1
Rookie
Thread Starter
Parasitic draw coming from AC fuse. What's the next step?
A couple months ago, the AC fuse (#9, 15A, A/C CTRL PNL) blew out on my 2007 ES350, and after replacing the fuse, a 150-250mA parasitic draw developed. Pulling out the new fuse removes the draw but also disables all the AC buttons on the infotainment.
Even though I found the faulty component, I'm stumped on what to do next. Do I buy a clamp-on ampmeter and individually test every wire for a draw and then splice & electrical tape off the ones that are drawing? Any other methods?
Even though I found the faulty component, I'm stumped on what to do next. Do I buy a clamp-on ampmeter and individually test every wire for a draw and then splice & electrical tape off the ones that are drawing? Any other methods?
07-06-22, 02:14 PM
#2
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Thread Starter
Did some more digging and disconnected all of the infotainment/AC cables today and there is still a 100mA draw when the AC fuse is installed. Now I'm truly stumped.
Last edited by cyclet; 07-06-22 at 02:55 PM.
07-06-22, 06:19 PM
#3
Intermediate
This is a tough one, the only way you're going to be able to find out is the chase the lead from the fuse all the way up and maybe find out where there might be some crossed wires.
Do you have access to a wiring diagram?
Do you have access to a wiring diagram?
07-06-22, 06:22 PM
#4
Rookie
Thread Starter
Unfortunately I don't have a wiring diagram. I feel like toyotadiy.com used to have them available for download but I guess they got taken down?
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07-07-22, 07:53 AM
#6
Intermediate
07-07-22, 09:11 AM
#7
Rookie
Thread Starter
Haven't yet. I was looking into it last night and the compressor seems difficult to get to since it's below the alternator. Haven't been able to find a way to reach the plug without taking out the radiator.
Edit: actually, reading through nevernu's wiring diagram, the A/C compressor actually has a relay. Let me try pulling this first...
Edit: actually, reading through nevernu's wiring diagram, the A/C compressor actually has a relay. Let me try pulling this first...
Last edited by cyclet; 07-07-22 at 09:22 AM.
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07-07-22, 10:11 AM
#8
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07-08-22, 01:18 PM
#9
Pole Position
Using the schematics, look for all components downstream from the fuse that blew. Based on your description of the event leading up to this, and what occurred after you replaced the fuse, I wouldn't necessarily be looking for "crossed-wires" or, some sort of short. If that was the case, the new fuse would have blown too. Instead, I suspect the current draw is from resistance in one of the AC circuit components. I would expect that none of these should be drawing with the key in off position (the definition of parasitic drain). Thus, look for components that could draw amps, if failed, while the key is off.
Sorry I don't have any specific ideas of where to look, but I'll check out the schematics provided and get back if I see anything.
07-08-22, 01:24 PM
#10
Pole Position
Did you test your MGC relay?
07-08-22, 03:31 PM
#11
Rookie
Thread Starter
I agree with the first part of this suggestion, but not the second.
Using the schematics, look for all components downstream from the fuse that blew. Based on your description of the event leading up to this, and what occurred after you replaced the fuse, I wouldn't necessarily be looking for "crossed-wires" or, some sort of short. If that was the case, the new fuse would have blown too. Instead, I suspect the current draw is from resistance in one of the AC circuit components. I would expect that none of these should be drawing with the key in off position (the definition of parasitic drain). Thus, look for components that could draw amps, if failed, while the key is off.
Sorry I don't have any specific ideas of where to look, but I'll check out the schematics provided and get back if I see anything.
Using the schematics, look for all components downstream from the fuse that blew. Based on your description of the event leading up to this, and what occurred after you replaced the fuse, I wouldn't necessarily be looking for "crossed-wires" or, some sort of short. If that was the case, the new fuse would have blown too. Instead, I suspect the current draw is from resistance in one of the AC circuit components. I would expect that none of these should be drawing with the key in off position (the definition of parasitic drain). Thus, look for components that could draw amps, if failed, while the key is off.
Sorry I don't have any specific ideas of where to look, but I'll check out the schematics provided and get back if I see anything.
Not yet, not sure where it is. I did pull the Magnetic Clutch relay though (downstream of the MGC) and there weren't any changes. Is the MGC accessible from the outside or buried in the dash?
07-08-22, 05:16 PM
#12
Pole Position
Another thing to consider is the electronic controls for the electric fans, as they will operate with the ignition off, and so, could factor in on an issue with parasitic draw.
07-08-22, 08:25 PM
#13
Rookie
Thread Starter
Was the Magnetic Clutch relay in the R7 position in the main fuse/relay box, under the hood? If so, that is your MGC relay. I believe the only thing downstream from the MGC is the magnetic clutch on the compressor. Do you know how to test the MGC relay? I don't have a manual for the 5th gen ES350, but someone who does could provide the test procedure.
Another thing to consider is the electronic controls for the electric fans, as they will operate with the ignition off, and so, could factor in on an issue with parasitic draw.
Another thing to consider is the electronic controls for the electric fans, as they will operate with the ignition off, and so, could factor in on an issue with parasitic draw.
My understanding is that a relay is like a big fuse designed for high-amp loads with additional functionality of being able to act as an on/off switch for a circuit. I could be wrong though, definitely not an electrical expert haha.
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