Battery Drain in 87 Cabriolet (Or Not?)

[Smoove1010]

Parked my 87 Cabriolet after a nice Sunday drive and neglected to put the tender on the battery for a couple of weeks. Found my 8 month-old DieHard AGM down to 2.25 volts. Resuscitated the battery and set about tracking down amp-parasites. An ammeter test showed a drain of .14 amps with key off, doors closed, but frunk open; the forum and interwebs say that under .1 is OK and .05 is better. Did more forum and internet re-searches, applied some of that knowledge, and found a few conundrums:
- All usual suspects checked, i.e., interior lights, glove box light, engine compartment lights - all are off, frunk light bulb is missing;
- Concluded that the power windows aren't supposed to work at all times, even with the key out and doors closed. Cleaned up the door contact switches as numerous posts indicate that battery drains can occur when these switches are dirty, which can cause the power window relay to remain energized at all times. Now the interior dome light works perfectly (on with doors open, off with doors closed) but my power windows still operate at all times. I thought they were only supposed to work this way on a cabriolet when a door is open(?)
- When connecting/disconnecting the battery, I hear a slight click behind the gauges, I'm assuming this is the window relay getting energized;
- When the frunk is closed, the parasitic drain drops to .09 amps - even though there's no bulb in the frunk light fixture!

Questions:
1) Is a .09 amp parasitic draw a problem?
2) Why would the parasitic draw increase to .14 when the frunk is opened even when there's no bulb in the frunk light fixture? Is there another device powered by this circuit, like the alarm system perhaps? (I can't find the luggage compartment light switch on any wiring diagram in Bentley.)
3) If my door contact switches are working properly, why is the window relay remaining energized when the key is out and doors are closed?
4) I pulled every frunk fuse and relay one at a time and none had any effect on the parasitic draw. Is the next step to pull all the under-dash in-line fuses, followed by those in the engine bay?

Any thoughts and suggestions would be most appreciated!

Thanks in advance,
GK

[wwest]

Originally Posted by Smoove1010

Parked my 87 Cabriolet after a nice Sunday drive and neglected to put the tender on the battery for a couple of weeks. Found my 8 month-old DieHard AGM down to 2.25 volts. Resuscitated the battery and set about tracking down amp-parasites. An ammeter test showed a drain of .14 amps with key off, doors closed, but frunk open; the forum and interwebs say that under .1 is OK and .05 is better. Did more forum and internet re-searches, applied some of that knowledge, and found a few conundrums:
- All usual suspects checked, i.e., interior lights, glove box light, engine compartment lights - all are off, frunk light bulb is missing;
- Concluded that the power windows aren't supposed to work at all times, even with the key out and doors closed. Cleaned up the door contact switches as numerous posts indicate that battery drains can occur when these switches are dirty, which can cause the power window relay to remain energized at all times. Now the interior dome light works perfectly (on with doors open, off with doors closed) but my power windows still operate at all times. I thought they were only supposed to work this way on a cabriolet when a door is open(?)
- When connecting/disconnecting the battery,

I hear a slight click behind the gauges,

Clock winding.....


I'm assuming this is the window relay getting energized;
- When the frunk is closed, the parasitic drain drops to .09 amps - even though there's no bulb in the frunk light fixture!

Questions:
1) Is a .09 amp parasitic draw a problem?
2) Why would the parasitic draw increase to .14 when the frunk is opened even when there's no bulb in the frunk light fixture? Is there another device powered by this circuit, like the alarm system perhaps? (I can't find the luggage compartment light switch on any wiring diagram in Bentley.)
3) If my door contact switches are working properly, why is the window relay remaining energized when the key is out and doors are closed?
4) I pulled every frunk fuse and relay one at a time and none had any effect on the parasitic draw. Is the next step to pull all the under-dash in-line fuses, followed by those in the engine bay?

Any thoughts and suggestions would be most appreciated!

Thanks in advance,
GK

[Smoove1010]

Clock winding? Not the power window relay becoming energized? Hmmmm...

Thanks for the reply.
GK

[steely]

GK - sounds like you're not having fun - the mysterious change in current would bug me.

You might try disconnecting the connector to the lamp and then testing that and or the trunk lid/switch to see if the current changes.
See this thread for the connector location:Trunk Light power connector ident

This circuit does have in input to the Alarm - in the schematic in the link above, the box identified as F34 is a feed to the Alarm, if you have one that is.
Sorry I can't shed any light on the power window switch operation.

[steely]

You might try pulling the power window control unit (has the relay), and then testing for the 'click' when you re-attach the battery.

The Bentley doesn't show the interior light ckts too good at all (lousy actually), yet it does reference them teasingly in almost every major system schematic. Central Locking, pwr dist, gnd dist, A/C & Heating, Anti-theft, Inst Panel and even Exterior lighting schematics all make a reference, but none show the actual wiring for trunk, engine, glove box, coupe/cab/targa lights.

[Smoove1010]

Dan,
I noticed the same omissions in Bentley - it's as though some of these things don't really exist.

I'm thinking the frunk light switch is connected to the alarm system to allow it to detect the lid being open, so when that circuit is closed, a 50 mA drain occurs which seems high to me for a system like that, but I only barely have a clue about these things. If there was a short somewhere in this circuit I'd expect a lot more current draw.

Though this posting: electrical problems - new battery drains overnight
had me thinking that <100 mA draw was OK (which means my 90 mA draw passes the test) the rest of the internet says I should be below 50 mA. Since my power windows are powered all the time, and since they apparently should not be, I'm going to follow that trail of clues. I'll probably follow your recommendation on yanking that module/relay.

My car's wiring seems to be in good shape, and only slightly molested by previous owners, but you never know when some wrench "solves" a problem with a jumper wire here or there.

Thanks,
GK

[msterling]

The power windows of my 88 Cab are not energized all of the time. Shut off engine, remove key, open door; kills power windows at last step. Interior lights have 3-way rocker switch. Off, on when door open and always on. You have a problem with switches or wiring or relays if it doesn't work like above. Both power windows and interior lights are related to the door switches. The frunk light is not related to the door switches but a corroded socket could cause a drain. Disconnecting the lead to the frunk light was a good suggestion.

The clock does cause a very small drain. Maybe 3-4 months to drain a good battery. Yep, I've done it.

[Smoove1010]

msterling - thanks for the notes. After reading many posts about the door contact-switch solution, I tested them both. The drivers side was OK, the passenger side was not making contact. I removed and cleaned them both, and put new rubber booties on them. The dome light goes on and off properly when the doors are each opened and closed. The power windows still work all the time though, key in, key out, doors open or closed, doesn't matter.

So even though the door contact switches are providing a ground to the "window control unit" when the ignition is off and key removed, the windows remain powered. Could this be a failure of the window relay, i.e., the relay is stuck in the closed position? In my experience, relays usually fail in the open position, i.e., the contact points get corroded and don't make contact, which should result in the windows being inoperable.

Could it be a failure of the ignition switch, i.e., there's always power to the red/yellow wire feeding the window relay even when the key is off and out?

Am I correct in assuming that "window control unit" "window relay" and "window control module" are all different names for the same thing on an '87 Cab?

Next step: Check all grounding points. Any other troubleshooting suggestions?

Starting to wonder if my intermittent power door lock system is related in some way...

Thanks again for thoughts and suggestions,
GK

[steely]

GK - The terms are synonymous in this case anyway(relay / control mod / etc).
The module is a relay driven with some electronics, which might be being fooled into thinking the doors are closed, and thus it may be commanding the internal relay on (enabling window power). So it’s not the typical relay (failure mode) you were thinking of.

I looked at my schematic, but it doesn’t show the module logic, so I searched and happened upon this thread below. Post 43 was interesting.

The relay module is supposed to power the windows when the IGN is on.
A feature keeps power to the windows when the IGN is OFF – until the doors open.
If the relay module goes bad and mis-interprets a good door switch, the relay mod will never shut off the window power (and be a vampire to your battery).

You might check the part number, there were 2 referenced.
My electric windows work without the key in the ignition

on edit - mind letting us know what you find? I'm no expert on this either:-)

[steely]

It may have been this relay that you heard click when you disconnected/reconnected the battery.

[steely]

post #8 from Gerry - he gives some great steps.Electric windows causing battery drain?

[Smoove1010]

Using methodical, scientific troubleshooting sprinkled with some trial and error, here's what I learned:
- It's the power window relay causing the parasitic draw. Confirmed that the relay was clicking when the battery was connected. Pulled the relay out, the draw went away;
- While the relay was out, tried the windows for kicks - they worked! Even with the PWR removed, the windows went up and down. Pulled fuse 1, they still worked! Scratch head!
- Even when fuse 1 is pulled, the red/blu wire is still energized. Bentley schematic 970-42 tells me that it should only be energized if the black wire on the other side of that fuse is energized by the relay. Scratch head again!

I start thinking that a PO bypassed the relay altogether, but I could not find any obvious signs of a jumper. Admittedly, I'm no wiring expert and it's very hard to see anything in that tangle of wires that weaves around so many other parts of the car.

I find another clue: When I pull fuse 2, the red/blu wire goes dead. With fuse 2 out, I replace fuse 1 (with the PWR installed) and window function returns to normal! They operate only with key in and on; when key is removed, windows work until the door is open. At least I know the relay and contact switches are good. But why is the red/blue wire getting voltage when fuse 2 is in place?

Fuse 2 is for the "seat adjusters" and "booster fan" according to the fuse panel label. I noted on the "Seats" schematic 970-44 that both the red/blu and red (always hot) wires have close proximity. I'm wondering if they are crossed somewhere in the seat adjustment system. Also noted two symbols on the schematic labeled "J/C (Blue Tape)" and "J/C (Red Tape)" - what are they? Below J/C (Blue Tape) there appears to be a connection between the red/blu wire and a red one - am I reading that right?

Could a malfunction or short in a seat adjuster system cause the window circuit to be energized?

Thoughts and suggestions welcomed as always...

Thanks,
GK

[steely]

smells fishy and I think you're onto something. The key could be the Red Tape Blue Tape junctions of which I know nothing. They appear to be power distribution busses. I wish I knew where this 'tape' / junction was physically located for you. Blue is also associated with seat heaters, red with power seats.

You might try disconnecting the plugs under both seats and seeing if that helps in the isolation quest.
And/or with all power off, fuses 1 and 2 removed, buzz (resistance check) red to red/blu (fuse 1 to fuse 2 load side) to see if they are in fact common.

[Smoove1010]

Thank you Dan. I'm officially abandoning this thread since the drain cause has been determined and the mission has now shifted to "isolation quest" as you aptly put it. I'll be following your suggestions, thanks.
I'm dismayed when I find threads that address my Porsche-puzzle-of-the-day but are left open-ended; for future Pelicans pursuing a problem similar to this one, the next chapter in this mini-saga is here: Power Window/Power Seat Circuits Crossed?.

Thanks!
GK

[steely]

oh man, you are welcome. I hope it was a bit of a help, and good luck with the new thread and issue. I'll be following it out of curiosity for sure.