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I've read a lot of back posts here and Adrian's book on the subject. I'm going to share what I've done and will do to track an irregular battery drain that can leave me with a very flat battery in a day or two.
First the groundwork -
1. I replaced my battery with an AGM from Napa. It's widely agreed there are only a few mfgrs of AGM batteries and I generally shop on price. Napa has great discounts in general and for AAA members, I believe I paid $150 or thereabouts for an AGM of same size/specs as stock.
2. Cleaned all grounds and battery cables
3. Checked charging voltage. I wasn't thrilled with the <14v I was getting and the variation I got with loads so I replaced the voltage regulator. Now getting rock solid ~14.2
4. Verified battery health during starting by using peak-hold volts on the fluke then again with a AESwave Uscope. Looks great, voltage above 10v min.
5. Checked parasitic drain. This is a complex one as disconnecting the battery kills power to a lot of the prime suspects. Doing it this " easy way" I see healthy numbers in the 30ma range. Tonight I will check the ignition-on current with a clamp meter to be sure its safe for my DVM to be hooked up in series then check the drain by turning the key to 'on', then turning off, opening doors etc all with the DVM in series.
I can already tell I am getting odd behavior from the power windows. With key removed the interior lights turn on and off as they should with the doors being opened but the power windows remain powered. I tried sitting in the car, removing key, opening both doors, closing both doors then locking myself in with key fob (T-Lock installed but no aftermarket alarm) and the windows still worked.
That's where I am. I'll post progress and welcome advice along the way.
Are your dome lights set to turn on with the doors opening? Are they coming on? If they're not, and your power windows have power with the ignition off and the door open, then that's your drain.
Check your door jam switches. Sometimes the switches can go bad but sometimes the rubber boots can interfere, especially in the winter when the rubber boot gets cold and stiff.
Yes, mentioned above they are coming on as intended. However the windows are behaving strangely. Most prior threads I've read link the behavior of dome lights and windows but mine are telling a divergent story.
Sometimes the lights behave a bit odd as well. For instance the light will come on when the door is open then turn off (door still open). But they do come on and then turn off with door closed after they time out or when I use the lock fob. They come on when I use the unlock fob.
I have cleaned the door switches and replaced their grommets as well.
Late edit to avoid any confusion- I mistakenly thought the window relay was inside the alarm ecu (ecu just provides the signal to the relay inside the fusebox).
Anyway, this is pretty universal-
Testing relays is pretty easy. A 9v battery will trigger the spring-loaded armature and make the typical “click” sound. You can also pop the cover off and make sure the armature moves freely and rub an emory board across the contacts (just like an old points ignition). Any 30 year old relay is bound to have a little contact corrosion inside.
The wiring diagrams have all of the pin info, though sometimes a pain to decipher which is which. I measured a pretty hefty ~90mA draw from the relay being activated. That’s what it takes for the coil to physically hold the armature against the force of the spring.
A few minutes with the central electric box has told me two things.
1. There is an issue with the AC condenser fan. Pulling either fuse 39 or relay 14 will reduce the parasitic loss by about a half amp.
2. The power window regulator circuit is definitely on the fritz. Pulling either fuse number 4 or relay 22 will eliminate the balance of the parasitic draw bringing me down to about .04 A
I say on the fritz because sometimes I can close the door then hear the regulator relay click off and sometimes I close the door and it will not. The behavior of the lights has nothing to do with this. The light behave quite well and always come on when door is opened then turn off about 10 seconds later.
Relays 4 and 14 are identical - by swapping them it looks like I have isolated relay 14 as bad. This is the ac condenser blower. I will replace it. Probably both.
I am still not certain about the power window circuit but an easy test is to always check the switch as I am getting out of the car. I would like to think that leaves me covered while I continue to diagnose.
Rus, I’ll be following your results in this thread. I have generally the same problems with erratic window and dome light functions. I’ve not been able to track down the problem so I’ve just installed a battery cut off. Haven’t had a chance to use the dial indicator mount yet either.
Today I cleaned the door contact switch again. It wasn't obvious to me the first time that what are effectively sheet metal threads (the body) is the contact point so I made a point of scrubbing the hole with Deoxit.
The Window Regulator Relay has a transistor in it so I can not be positive of its behavior but I believe one option would be to send pin 4 to constant ground, either by picking up a central electric terminal bussed to 31 or simply via a ring terminal on GP-VI*. This ought to result in windows that work like most cars which is to say when the key is out of the ignition the windows do not work. Another poster suggested the opposite - leave windows 100% hot but that makes less sense to me personally.
*I am almost finished with an H4 relay kit integrated with the Central Electric fuse box so I know my way around making and changing terminals.
Not sure the benefit of a rewire unless there is a deeper issue.
If that relay is working right
And your switches are working right
You should not have a parasitic draw
The way it's supposed to work is that when key is on windows work. When key is removed and off, windows will work, until the door is opened.
If that 'trigger' does not work right, it can leave the relay in a 'windows work' state and cause a draw
This should be easy to test, meaning:
doors closed key on - windows work
remove key - windows work, if the stop working, bad
open door - windows don't work - if they do, bad
Yes on all of above. However. I am not convinced that lights on = windows off = end of story. The grounds are ganged together and anyone who has experienced a marginal ground knows that current does funky things. I've seen brake lights illuminate indicators on my Alfa and the culprit was precisely the same thing: light assemblies grounding thru sheet metal screws not proper grounding posts. I believe its possible the switch can trigger the lights but the windows can remain on - in fact I have witnessed it.
Therefore my proposed mod is a fail safe. Presumption is that if my switch acts up in the future and I don't catch it (let's face it I am not going to test my windows every single time I get out of the car) I would rather give up the pre-door, post-key-out window functionality and save my bacon/battery.
A while back I found my window relay (main panel) was hot even though the car had been off for a few days. Apparently it was staying energized, and after being hit with emery cloth and electrical cleaner it’s been functioning properly.
Battery drain has been a nightmare on my 912, luckily didn’t have this issue with my 3.2, but it can be so frustrating, something as silly as an engine bay light could be causing the drain, you just have to test everything
I may be in the minority but I enjoy electrical work unlike say a random misfire or cold start problem it is relatively easy to test and isolate components one by one usually without replacing them or spending money.
I removed every fuse and relay and the problem is not a great mystery I’m just debating the best way of solving it. I will be back in the central electric box this weekend completing my relay install and will test my theory on the window regulator ground.
It’s funny how on a new car, I love all these advanced controls and complex algorithms. Now on a classic car or hobby, where it’s only driven on weekends and sunny days, I feel like things like the window relay, CCU, or the central warning light are just annoying.
If you've owned a 3.2 or any earlier car that you attempted to daily, you look at the CCU with a mix of awe, gratitude and fear. The usability difference between the two cars is vast and the CCU is to thank for much of it.
The fancy window behavior and frankly the alarm I could take or leave. Tore's keyless entry is a mega-win.
01-13-2021, 03:30 PM
Tracking down a battery drain
