bobinyelm

2003 RX300 51,000 miles

Over the past year, our relatively low mileage '03 RX has been sometimes (but not always) draining the battery flat on my wife's car if allowed to sit unused for more than a few days.

I've done searches, and this is not an unknown situation, but in our case, it appears to be intermittent.

Immediately after shut down, only the DOME and ECU-B circuits indicated a sizeable drain (using a millivoltmeter measuring across the fuses), which allos measurement without disconnecting the fuses, possibly "waking up" any modules powered by the circuits.

After 20 minutes, however the DOME showed only 12 ma drain, and teh ECU-B circuit was down to 50ma, again quite reasonable.

As a back-up I used a DC Clamp Ammeter on the battery cable supplying the vehicle's systems, and measured about 60ma (accuracy +/- 3%). The battery cable to the starter indicated zero drain, so the two tests correlated nicely.

That leaves me thinking I MISSED something, or the draw that drains the battery is intermittent, only happening once in a while. I guess I could run the same test daily until I luck into having one of the circuits showing itself while I happened to be measuring, but that seems a long shot.

I was wondering if anyone here has seen or heard of a circuit, or circuits prone to intermittently refusing to "sleep", causing a flat battery? I tend to think that mine is not the only RX300 to exhibit intermittent parasitic drain, and hopefully mine has the same circuit responsible.

Of course, any other ideas/suggestions are most welcome!

Bob

salimshah

How old is the battery? Have the battery tested at any auto shop that sells a battery,.

At times one should follow the easiest way out.

Salim

bobinyelm

Less than 8mo old after a similar incident with the "old" battery that was also less than a year old.

Just re-checked the draw at all of the small under-hood fuses (not the large 40/50a fuses) and it's under 50ma, and the main battery lead.

I tend to doubt I have had 2 bad batteries in a row, and I am going to check the charge voltage to make sure it's fully charging the battery, though it cranks the engine very well. With the battery disconnected, which I did recently when the vehicle wasn't used for a 5 week period), it spun the engine over after being re-connected.

This time, for 9 days of non-use, we did not disconnect the battery (I figured 9 days was not an issue, even at 60ma constant drain*) and it was 100% flat (which is very bad for a starting battery, of course). When "home," and in more frequent use the vehicle has sat for 4-5 days w/o being started and it cranks at its usual high rpm, so I was wondering if the parasitic draw is intermittent.

I know recently my Mercedes almost flattened my nearly new battery overnight when a module evidently stayed awake (After a lot of reading, I found my model is prone to having insomnia in its seat control modules, so I unplugged them, which really only affects the multiple seat memory, and no repeats of the problem so far).

Bob

60ma drain = 0.06 X 24hr/day X 9 days = 13amp-hours, or only about 1/6th battery's full amp-hour capacitiy.

salimshah

If you search through the old threads, your 80mA is trivial and good battery should be able to handle that without problem .. that is why I suggested having it checked. uglily but you can have 2 bad batteries in a row.

Can it be that your measurement is wrong.

Other possibility is what ever was drawing is now off line.

Salim

bobinyelm

Yes, 80ma should be no factor. I left a milliammeter attached today and watched it at times all day, and it never exceeded 60ma. Mostly bounced 50-60ma.

I am inclined to believe that some system is not going off-line at times, and remains "live" at intermittently odd times causing a heavy draw, with the result being a dead battery. That's what was happening w/ my Mercedes, and after reading the usual suspect list, and pulling the electrical plugs to my seat modules, I have not had the same problem again (so far).

The "trick" is to find WHAT is staying on once in a while, causing the dead battery on the RX300. That's why I was hoping someone would have heard or read of a "likely suspect" on it, as with the MB.

What would be useful would be a device that would alert me if the battery were being drawn more than, say, 100ma, while the vehicle was inactive. It's not practical to undo the battery connector frequently and actually stick a current monitoring device in-line. Most current measuring devices capable of resolution down to 100ma will not stand the high drain of the vehicle in operation, though the battery connector has two detachable leads, one that feeds the starter (that can see perhaps 100 amps at starter engagement), and the other feeds the rest of the electrics (and never sees more than 50 amps).

I do have a battery tester that claims to test the battery with a 100 amp load. I can't verify the amperage, but the load wires inside throw a LOT of heat when activated, so maybe it's accurate, but I can check that with the DC Clamp ammeter I suppose.
https://www.harborfreight.com/100-am...ter-61747.html

salimshah

Just measure the R of the load and apply ohms all V/R (measure the dropped voltage when you connect the load.

I dont want to start an opinion war, but if you allow me some latitude, Nippon electric produces better product than Lucas and Bosh. Problems reported here have been few and here is the rank order
1. Add on accessory
2 Dome light/vanity light glove compartment light left on.
3. Door actuator registers the door as open.
4. Bad battery.

Salim

bobinyelm

Yes, I could measure the resistance of the load wire in the battery tester and use Ohm's law, so E/R=I in amps. For a true 100a load, the R would be 12/100= 0,12 ohms, a small enough value to be difficult to measure. Plus, if the wires get hot enough with 12v connected to them, they will change their electrical resistance value.

No argument about Nippon vs. Lucas for sure (The only thing Lucas built that didn't suck was their vacuum cleaners.), and I can't say that Bosch today is the Bosch of old, either, when they were pretty decent.

1) The car is 100% stock with no add-ons at all (unfortunately-that would be an easy solution). While the car has only 51,000mi, and looks and runs like new, and is garage kept, and almost never has been driven in the rain, or on wet roads, it is very old now and components could be failing simply from age.
2) No lighting switch was changed from when the battery was killed to when I measured proper drain. I even checked the visor vanity mirror switches because one chap reported his switch failed, powering the light with the mirror door closed.
3) If a car door thought it was open, the ceiling light would likely have been on (though perhaps the light would have been dimmed to "off" after a delay by a lighting module as with many cars these days.

I tried to find what the system uses to sense a door open, but saw no switch anywhere in the door jamb unless I missed it. Maybe you know what the RX300 uses to sense a closed or open door? (Magnetic proximity switch, or other non mechanical switch?)

I would like to be able to prop open the door yet have the car system be fooled into thinking it was closed so I could take measurements with the door open, but the car thinking it was closed.

4) I'll know more on that after I hook up the battery load tester and see how the battery holds up under an extended load. An alternative would be to hook up a 10 watt wire wound ceramic resistor of perhaps 10-15 ohms to see how long the battery would hold up under a modest one amp (approx) load that should kill the battery in about 80 hours or so. This is one of those times when I wish Radio Shack was still around for easy access to such things.

I will keep looking for the problem because my wife now doesn't even want to drive the car, having totally lost confidence in it. She went so far as checking with Cars.com, who offered only $2800 for it, but no way am I going to see an absolute mint Lexus with 50k miles go for that price, especially when they want $18,000 for a 2010 RX350 with 110,000mi on it that could have worse issues!

salimshah

FYI:
Door ajar sensor is part of the door lock actuator.

Salim

maxSteel

I'm curious about "Less than 8mo old after a similar incident with the "old" battery that was also less than a year old."

Are you saying you had this problem 8 months ago and then after replacing the battery the problem went away?

bobinyelm

OK, so to trick the computer, I just need to click the door catch cog to the closed position while I am mucking about.

Yes- the problem didn't present itself for another 8mo because when my wife was away for an extended period of over 10 days or so, we just disconnected the battery each time. This time, we hadn't had any drain issues even when the car wasn't driven for several days, so we got "lazy" and left it connected for 9 days of her absence this time, resulting in a completely dead battery. I should have monitored the battery drain during her absence, but did not. I will start leaving the hood open and checking the drain several times each day the car isn't used. In the winter, it seldom gets driven because she doesn't like driving it on wet roads and likes to keep it showroom new by using one of the spare "winter vehicles" we keep for the purpose. It does get used enough to keep the battery charged, and sometimes put a charger on it as routine. I just didn't do it THIS time. It ordinarily gets driven about 60mi per week. It always spins over like a turbine when cranked, so the battery normally stays well charged.

That's why I suspect very occasionally, something or a module stays awake when it should have gone to sleep, presenting a bogus drain to the battery. I didn't know if any such modules are more likely than others to go "south" in this way.

ukrkoz

https://www.wikihow.com/Find-a-Parasitic-Battery-Drain

brandon736

Bill Dowd

YOU COULD HAVE THE FOLLOWING PROBLEM Diode failures may also allow AC current to leak into the electrical system. AC voltage creates electrical “noise” that can confuse electronic modules and digital communications. A leaky diode also can allow current to drain out of the battery through the alternator when the vehicle is not being driven.

britspeak

I bought a very well maintained 2002 Lexus RX 300 in great shape with 143,000 miles in early April 2018 and drove it regularly. However, by May 15, after a period of not being driven, the car battery went dead. Replaced battery but the issue was not fixed. Car had to be jumpstarted several times, and required regular driving of some distance to stay charged or go dead on the second day. Regular mechanic suggested a parasitic draw so I took it back to the dealer's original mechanic, who went through everything over several weeks and could not find the source. Regular mechanic also went in and could not find it. Now at Lexus, who also can't find it after about 10 hours. Suggesting an issue in one of the computer modules but now thinking it's in the wiring harness. Perplexing everyone and Lexus wondering if it's worth me spending a lot more money even on diagnosis, and if a new wire harness is required I'm told it's thousands. I only paid $7.5K for the car. I'm up to nearly $600 or so with all attempts to diagnose it but it's a pain. Wondering whether to cut my losses and sell at a loss with disclosure of parasitic draw. Looks like other people have had this issue, although the Lexus dealer said it is extremely rare. Wondering what others found was going on? Dealer who sold me the car and his mechanic swear the car was perfect when they brought it in and the dealer is suggesting that AAA and my mechanic must have done something to cause a short in the wiring. I or they have done nothing out of the ordinary, so this just seems like blowing smoke to me. Trying to figure out how to proceed now as this has been going on for months.

debor300

I just acquired a Lexus rx300 from 2001 with 130,000 miles. It has a parasitic drain. I isolated it to fuses 15 and 16. I took it to the mechanic who traced it back to the computer multiplex network unit part 89221-48031. when he removed this part from the car the amps dropped off. Now I am looking for a place to purchase the part. I found various websites but want to find a reputable site. Any recommendations? the dealer wants over $800.