Normal Battery Draw

[Pstallo]

I've been checking fuses and sorting through lights and switches to try to find a parasitic battery drain that empties my battery in 3 days.

It turns out it's the fuse that powers the interior light, luggage light, engine light, and clock.

I removed the clock (which doesn't work anyway), made sure the glove box light was off and pulled the bulbs from the interior light and the luggage light and I'm down to a parasitic drain of 50 milliAmps.

I noted that it goes up to 90 miliAmps when I open the door even if the interior light bulb is removed.

Is 50 milliAmps a normal draw for an 86 911 or should I keep looking for the cause?

[pors1968]

Check the door jam swith it may not diactivate your electric window relay.

[nene]

I'm in the same boat, but don't know where to start.

[rick-l]

Originally Posted by Pstallo

I noted that it goes up to 90 miliAmps when I open the door even if the interior light bulb is removed.

In the convertible (at least mine) when you open the doors the windows work without the key in the ignition. The 40 mAmps must power the relay.

50 mAmps is less than my 88

[T77911S]

with the battery not connected to anything,does it hold a charge.

[Pstallo]

The battery does hold a charge. I first thought it was the battery so I replaced it with a brand new Odyssey and the car went dead a few days later. I then installed a kill switch so I could at least disconnect it easily. With the kill switch off it hasn't gone dead yet.

I'm just trying to track it down because I sometimes forget to flip the kill switch and it goes dead again.

50 Amps must be about average for that age car, so hopefully I fixed it about as good as it can be fixed.

[Smoove1010]

I just went through this, and in my case it was the power-window relay remaining energized when the key was off and out. Battery Drain in 87 Cabriolet (Or Not?) Apparently a typical reason for this is the door-jamb button becoming corroded and inoperative, but in my case the culprit was a hack by a PO (or his creative fix-it guy.)

There are many threads on this forum about parasitic draw (and on forums for other cars as well.) My investigation also led to my finding that the fuel pump was hotwired and two circuits were incorrectly bridged, the saga continuing here: Power Window/Power Seat Circuits Crossed?.

I'm now down to a draw of less than 50 mA, and the battery has stayed above 12.5 v for weeks without a tender in a garage that's been between 40 and 45 degrees F. Once it gets below 12.5v I'll note how long it took and put the tender back on.

Once you get started on these investigations you have to go where the evidence leads you...

Good luck,
GK

[SpyderMike]

Here is a picture of the door switches from my 1985:



The contacts should be shiny copper I believe. These are heavily oxidized and there is high resistance even with door closed (acting as if the door was open).

I tested my trunk light and the same condition exists.

Just a suggestion, if you were to remove your power window relay and test the drain what does it say?

Then remove the relay and test the socket location 85b to ground looking for resistance with all doors/trunks closed to see what you get. You should have an open circuit, right? You can then open one at a time to see what each switch reads to narrow it down.

Looking at the relay schematic, it looks like pin 85b is connected to the always hot bus 30 through an capacitor internal to the relay? Is this a correct interpretation?

Have you tested the draw after the power window relay times out - give it a minute or two?

[scarceller]

With the key out and door closed reach in the window, do the power windows work? They should not.

[SpyderMike]

Isn't there a timer circuit in the relay which allows for windows to work for a while after the doors are closed?

Here is a link to an interesting description of the functioning of the relay as it relates to the power windows. Unfortunately, it doesn't relate to the interior lights. However, with my feeble understanding of electrical schematics, the door switches are integral to the power window timer/sensing part of the relay.

911 Power Window Troubleshooting - Dorkiphus.net

[scarceller]

Originally Posted by SpyderMike

Isn't there a timer circuit in the relay which allows for windows to work for a while after the doors are closed?

I believe so, just leave the window down then come back to the car in 1/2 hour reach in and see if windows work but don't open the door. They should not work if they do you found the issue.

[Pstallo]

I turned the key, rolled the windows up and down a bit. Removed the key and the windows still worked, so I tried opening and closing the driver door with the key removed and they still worked.

So, I unplugged the power window relay, waited about a minute and tested again and the draw dropped immediately from 50 milliamps to 30 milliamps which I figure is probably a reasonable draw on an older car.

Do you think I just need to try replacing the door-close switch? Or, could a bad relay cause a leak like that?

[scarceller]

The window relay has some sort of timer in it so you need to remove the key, close the door and then I'd wait 15 minutes. Then come back to the car reach in the open window (do not open the door) and see if windows still go up and down. They should not.

[darrin]

on my '86, when the driver's side door light pin switch failed (interior lights would not illuminate when the door was opened), the windows would continue to operate (and draw current) indefinitely. Put another way, I discovered the problem several days after I'd turned off the car and removed the key.

Conversely, when I opened the passenger door (which had an operational pin switch that illuminated the interior lights), the windows immediately ceased to function and would not operate until I inserted and turned the ignition key . . . fixing the drivers door switch eliminated my parasitic drain problem and allowed my '86 to sit for several weeks without significant battery drain (up from the 5 day max before I discovered the door switch issue)

[Pstallo]

I think you hit another note darwin--my interior light doesn't come on when the door is opened, but turns on if you rock the light switch to on. Looks more and more like a faulty door switch.

[Smoove1010]

Originally Posted by Pstallo

I think you hit another note darwin--my interior light doesn't come on when the door is opened, but turns on if you rock the light switch to on. Looks more and more like a faulty door switch.

I'd start with this - check both door switches. They are ultra-simple, just take them out, check the contact surfaces, clean them up and re-install. The switch grounds the wire to the body, so make sure that the mounting surface is making a good ground. Just don't let that wire fall into the door jamb! When done, if your interior light goes on and off as it should when the doors are opened and closed, then you're good.

[LJ851]

Originally Posted by scarceller

The window relay has some sort of timer in it ...

I believe this is incorrect.

When you stop the car and turn off the key, the power window relay stays energized until you open a door. The opening of the door unlatches the relay.

[Smoove1010]

Originally Posted by LJ851

I believe this is incorrect.

When you stop the car and turn off the key, the power window relay stays energized until you open a door. The opening of the door unlatches the relay.

This is how my '87 works. After all was fixed I could hear the relay click when the door was opened.

[Pstallo]

I've got new switches on the way, so I'll be sure to post back the results for anybody else who has the same issue.

[rick-l]

Originally Posted by LJ851

I believe this is incorrect.

When you stop the car and turn off the key, the power window relay stays energized until you open a door. The opening of the door unlatches the relay.

He has a cab so it should work like this: Power window logic relay 1988 911 cab (what is the point of this?) just an OR function.

I thought it was supposed to work as you described so I thought it was broken and was trying to fix it.