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1998 Cadillac Deville Sedan
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Discussion Starter · #1 ·
This is the second time it happened in the past month and a half - comes out in the morning and the batteries(I have two, one up front and one in the trunk) are dead, so dead that no dash light comes on, power locks don't work, no interior lights, etc... the only thing that kind of worked is the trunk pull-down motor. The two batteries has been installed in my car for about 3 years with no trouble and they're identical.

I have an aftermarket stereo installed and my headunit didn't work after the batteries died previously so I thought it was something along the line of my stereo, I unhooked everything(been driving without a radio for a month now) associated with my car stereo but now I don't really know why it happened again. Car runs fine after a jump and starts like usual.


I went on a business trip a few weeks ago and my car was sitting at an airport for almost two weeks so I thought it would be dead when I come back but nope, it was perfectly fine.


My question is can a slightly misaligned trunk pull down motor keeps running when it's not suppose to? I do see that the pull down motor only stops pulling if the metal tab flips the small switch on it, so technically it'll keep running until either the trunk is open again or that small switch gets flipped. I replaced the entire assembly with an used one I have laying around so hopefully it doesn't do the same again.


I hope it isn't something else because then that's a whole different ball game.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Knotty problem. IF the two batteries are permanently connected in parallel, then ANY voltage difference between the two will cause a "charge me, I'll charge you" reaction between the two when the engine is off and the car is idle. It's exactly like a slinky going down stairs - the net result is that the batteries mutually discharge each other. Unless one battery has a dead (or dying) cell, this self-discharge would not happen overnight, but it's entirely possible that both would be completely dead within two weeks.

Install an isolation switch in the "second" battery positive lead - not the underhood unit, the trunk unit. yes, PITA to use, but..........

Charge, then load test, each battery separately.
 

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1998 Cadillac Deville Sedan
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897 Posts
Discussion Starter · #3 ·
I've read about the self-discharge but it doesn't happen overnight - and both times my batteries died over the span of 8~10 hours. I know the charging system is fine because I had to wait a long line to wash my car yesterday and I had to restart my car like 6 times within an hour to move along the long line. I then drove for another hour or so before parking the car in the garage, no warning lights or anything abnormal.


I hope it's the trunk pulldown motor because that's the last "feature" I used before turning the car off. The one that was in my car was jammed and I fixed it by taking it apart, but while doing so I see that the height of pull hook is adjustable, I didn't have it aligned to the correct height(motor was PITA to reinstall) and my trunk lid gets pulled down a wee bit more(like 1/8") than before. Maybe the weatherstrip sat a bit off and the motor was having a hard time pulling down and ended up running the whole time until my batteries died.
 

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1998 Cadillac Deville Sedan
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897 Posts
Discussion Starter · #5 ·
If the trunk pull down motor was not turning off you'd be able to hear it running.
Yeah and I'm suppose to hear a "click" a few seconds after shutting the trunk lid which means the motor has stopped. But it's one of those things that are often overlooked... I grabbed the groceries, shut the trunk and walked inside.

If my car's battery dies again then I'm going to look for another car. There's a white 97 Deville concourse in town with 120k miles for like 4500... but man, there are so many things that can go wrong with these caddies that I might hop over to something simple like a Nissan Versa or something :suspense::cookoo:
 

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06 CTS
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You can disconnect the pull down motor without losing the lock function. I just did it on mine becasue it didn't work. I manually set the desired height of the "grab" latch. In the warmer weather I will replace the motor. Works like a trunk without the luxury!
 

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1998 Cadillac Deville Sedan
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Discussion Starter · #7 ·
Well I replaced the pulldown assembly & motor with an used one that I had sitting around and now it seems fine, no dead batteries. I'm gonna keep an eye on it though.
 

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09 1SG STS4 & Subie CrossTrek (retired 03 DeVille & 05 V6 SRX4)
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That happened to me 2 weeks ago, the battery died overnight, the day before everything was normal, no warning lights or dash warning, next day nothing, like someone disconnected the battery!
 

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1998 Cadillac Deville Sedan
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Discussion Starter · #9 ·
That happened to me 2 weeks ago, the battery died overnight, the day before everything was normal, no warning lights or dash warning, next day nothing, like someone disconnected the battery!

I'm getting an Optima yellowtop tomorrow since my current batteries are ruined - car is sitting at 10.0v with keys in the ignition haha. I think what happened is snow got in between the trunk seal and the motor didn't pull far enough to hit the shutoff switch so it just kept running until the battery is totally dead.

Seriously I can do without the stupid auto trunk pull-down feature, I'm not that weak.
 

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85 Coupe Deville 4.1 V8 & 4.3 V6 Deisel & 1970 Eldorado
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I do not know what is causing your battery drain but draining 2 fully charged 60 amp hour batteries flat in 8 to 10 hours would require quite a power drain. I am not sure how much power the pull down motor is capable of drawing. You would need about a 10 to 15 amp draw to do that assuming the batteries are in top condition and fully charged. I imagine your batteries are rated better than 60 amp hours also. With a drain this large, Finding it would not be too hard as long as it wasn't intermittent.

Good luck and happy discharge hunting!

PS: I am pretty good at tracing down discharge problems like this and can give you a few pointers on how to narrow down the offending circuit. I had to do this as a consultant to a major Cellular telephone Carrier when installation disputes arose.
 

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1998 Cadillac Deville Sedan
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Discussion Starter · #11 ·
You would need about a 10 to 15 amp draw to do that assuming the batteries are in top condition and fully charged. I imagine your batteries are rated better than 60 amp hours also. With a drain this large, Finding it would not be too hard as long as it wasn't intermittent.
The fuse for the pulldown motor is 20a but I think it only uses about half of that, and yes it is intermittent... it only happened twice in the past three months but that was enough to kill both of my lead-acid batteries. I do have a multimeter so wanna give me some hints on testing the circuit? There are so many fuses in this car that it's gonna take me awhile to figure out especially when it doesn't happen all the time, and when I do find out it is when I'm trying to go to work in the morning :hmm:


I really hope it is just the pulldown motor glitch because otherwise I'm going to have to buy another car and put this one away.
 

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85 Coupe Deville 4.1 V8 & 4.3 V6 Deisel & 1970 Eldorado
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One of the quickest methods to track down an errant current draw is to connect an amp meter between the negative battery terminal and the negative battery cable. You can then remove each fuse one at a time and see which circuit kills the draw. You would need a multimeter with a 20 amp current setting. Most multi meters only have a 10 amp setting and some only have a 2 amp setting. 10 is usually enough but you seem to have a larger draw then most. You could use an old auto amp meter gauge if you have one around especially with the high draws you are experiencing.

Disconnect the negative terminal and hook one lead up to the battery negative and hook up the other meter lead to the negative battery cable you just un hooked. The meter should show the standby current draw. The draw should be under 120 MA. usually in the 15 to 50 MA range.
This is normal. If you see anything more, Something is running that shouldn't. Remember opening the door will cause all sorts of circuit activation. (Interior lights, Security system and others) You may need to tape the door switches closed.

Now you need to be careful with a multimeter that you start on the highest current setting as exceeding the rating can blow the fuse in the meter. I also recommend using the negative terminal instead of the positive as there is less possibility of slipping with a wire and causing a short. DO NOT connect an amp meter on both a positive and a negative terminal! You want the meter to be in series with the system NOT parallel. Also DO NOT try to start or run the car with the meter hooked up as the starter draws MUCH to much current for the meter to survive.

This all assumes that the intermittent problem is occurring when you test it. Intermitt's are the worst to track down.

You should also not perform this test unless you are comfortable with a meter and working on electrical systems.
 

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1998 Cadillac Deville Sedan
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Discussion Starter · #13 ·
Well my car is totally dead again today :halo: I just bought a brand new Optima yellowtop a couple of weeks ago too, hopefully it didn't damage it.


I have a DMM but it's only rated to go up to 10 amps but i think it should be enough. I scheduled an appointment at a car shop but I'm going to use your method and see what's going on.

...and yes it is intermitts :crybaby: I'm pretty pissed off right now.
 

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Discussion Starter · #14 · (Edited)
Okay I just checked it the way you told me and the amp draw is at 1.314 amps with the car off and doors shut and nothing else on, it stays at that draw for about a minute or two then it drops down to about 180mA. After about 10 minutes it dropped to 17mA.



Okay when I pulled the BODY 3 fuse(50a) under the hood(it's under the black shroud of the smaller fuses) the amp draw drops to zero. I put the fuse back and it goes back to 1.31a then drops down but it doesn't seem like it has a steady draw, jumping from 300mA to 400mA or so. Does that mean anything?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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From your measurements it appears that RAP (Retained Accessory Power) is functioning as designed. You're good. Your car will ALWAYS drop down to the 17- 20 mA draw. That's keeping all the memories alive. And it's the reason every car lot has a battery charger sitting between the cars all the time.................

Your dead batteries are not the fault of RAP.

And what conditions did you change from paragraph 1 to 2 - the 17 mA draw to a fluctuating 300-400 mA draw ??? Does that drop after 10 minutes ???
 

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Discussion Starter · #16 ·
And what conditions did you change from paragraph 1 to 2 - the 17 mA draw to a fluctuating 300-400 mA draw ??? Does that drop after 10 minutes ???
That is after I pulled the BODY 3 fuse, I left it for about 10 minutes but the draw never came back down to 17mA, it hovered around 300~400mA. However I think it's because I opened the shut the trunk during that time or maybe I opened the door before 10 minutes was up.

Still that isn't enough draw to completely drain the battery overnight... I have no clue right now.
 

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Discussion Starter · #17 ·
I gave up - car is now at a dealership getting checked out(free of charge since my uncle is good friends with the owner), if they can't figure out then it's going to another mechanic that also owns a 98 Deville. If he can't figure out then... it is the end for this caddy as I know it. I feel like I lost an arm and a wingman :mad:



Unexplained, intermittent parasitic drain is really rare but it just has to happen to me.
 
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