Mystery Voltage Draw

[Bob Eyres]

We are trying to cure a long time problem with my ZR-1.
I find that if I don't keep a battery minder, or low voltage charger, on the car it will draw a fresh battery dead in 3-4 days.

I've got a friend with a voltage tester, and he says it's got about a 3 amp draw on the battery at rest with nothing turned on.
That seems like a lot. In fact it should be about what?... a half amp if nothing's wrong?
We don't have the ZR-1 electrical manual to refer to. So I'm wondering if you guys have run into this problem in the past, and what was the solution.

I know it could be a number of different things, but I'm trying to find the most common solutions, to narrow down the search.

TIA

[GOLDCYLON]

We are trying to cure a long time problem with my ZR-1.
I find that if I don't keep a battery minder, or low voltage charger, on the car it will draw a fresh battery dead in 3-4 days.

I've got a friend with a voltage tester, and he says it's got about a 3 amp draw on the battery at rest with nothing turned on.
That seems like a lot. In fact it should be about what?... a half amp if nothing's wrong?
We don't have the ZR-1 electrical manual to refer to. So I'm wondering if you guys have run into this problem in the past, and what was the solution.

I know it could be a number of different things, but I'm trying to find the most common solutions, to narrow down the search.

TIA

Do you have a side and top post battery ?

Make sure your mirror lights are off.... the ones in the sunvisors.

[Jagdpanzer]

Should be less than 20 milliamps with eveything off, key removed so CCM goes fully asleep. With this small amount of drain a good battery should last for weeks.

[WVZR-1]

What year is the car? I believe the newer cars with the under-hood fuse boxes are likely much easier to trouble shoot. Is there any added accessories? After-market radio or alarm etc.

Eliminate the most likely by removing the connector to the H/L module and disconnect the H/L motors AFTER you've walked around the car with the doors closed and the lights out in the garage, if it's an earlier year check the spare tire light.

[secondchance]

I had a similar situation with battery going flat in a day or two. In my case it turned out to be HVAC fan controller gone bad. Even with the ignition turned off the controller was running the fan at very low speed. Not saying your cause would be the same but worth checking out.

[Marc Haibeck]

I encountered a car that drew about 60 ma all of the time. It would drain the battery in about two weeks. The current draw was on the ABS power line. I eventually found a LoJack system, including a back-up battery for the LoJack, under the black panel under the rear of the hatch glass.

[Bob Eyres]

Thanks guys, I'll check this stuff out. The car is a 91' with no non-stock electrical accessories, Lo-Jack etc.
We thought it might be the headlight motors, but after replacing the gears and re-assembling, it's still pulling 3A. I'll let you know how it shakes out, and if anyone has other ideas, feel free to post.
Thanks.

[Bob Eyres]

Do you have a side and top post battery ?

Make sure your mirror lights are off.... the ones in the sunvisors.

Nope, Delco side post only. I'll check those visors. That would be an easy fix :thumbsup: thanks

[-=Jeff=-]

My buddy had a similar issue with a 1992 Thunderbird

We used a DMM set for current and connected in series on the positive post to the positive cable.

Then we started pulling fuses and watched the current looking for the drop off.


If you had the FSM you could narrow it down further by just looking for the 'always' hot connections..

Maybe check the door chime module? I think I have heard that causing issues ( just don't remember where I heard that)

[GOLDCYLON]

Nope, Delco side post only. I'll check those visors. That would be an easy fix :thumbsup: thanks

Bob don't forget pull it into a dark garage to make sure all the lights are off as WV suggested. You might have a duff door switch or rear hatch switch leaving the lights on including the spare tire light as well. GC

[WVZR-1]

I've never needed to do a "parasitic draw" test on a '91 but I believe if I had a parasitic draw on a '91 I'd start with doing a complete test of the DAB (Delayed Accessory Bus) first likely. A first year feature?

Determine how you want to do the parasitic draw test and be very systematic with your procedure. I've always used the - post and cable BUT ...

I've a friend who whenever doing a parasitic draw test didn't go to the fuse box but to the fusible links first. On a '91 aside from the ECM FL and the AC BCM FL all fusible links are at the junction block behind the battery. I might remove the fender panel and do it from there in an attempt to isolate the circuit.

I believe it would eliminate the need to remove the right side knee bolster to check the AUX BOXES where there's a pair of fuses for the convenience lighting and also the accessory leads in the console (another first year feature).

**** You do need to do a "load test" on the battery and confirm the condition FIRST!

[Jim Nolan]

I had something close to that in my '87. It drove me crazy for the longest time. Only by accident I found that it was the up position on the passenger power window switch. When I replaced both switches (passenger and driver) I found out why. What piece of junk.

Jim

[Bob Eyres]

Bump

[GOLDCYLON]

Aftermarket Radio? Burgular alarm ?

[-=Jeff=-]

Maybe the Door/Key/headlight chime? I heard that could be an issue too

[WVZR-1]

Bump

I don't quite understand the "bump". What have you done for a start?

[Bob Eyres]

Sorry guys, I got distracted by some higher priority stuff.
But we narrowed it down to a short in the the seat controls on the console before I had to stash the car in a safe spot for this (non)Hurricane that was coming. So I'll let you know how it shakes out his week.

Thanks for all the feedback :handshak:

[Locobob]

I noticed my battery getting drained when sitting for a few days, just discovered my passenger side visor mirror light was on... DOH!

[Bob Eyres]

A little update here. I'm away from the car and just had a phone conversation with the guys that are working on it.
Last week they told me that they'd found a shorted out driver's side seat switch at the back of the console, (I never knew the seat motor didn't work because I never really move it.). We ordered a switch from a salvaged C4 and installed it along with the harness and plug it came with. Now the seat works, but it kept blowing fuses.
Today they tell me that in the power supply harness to the seats, after they unwrapped the tape on it they spotted a fried 3amp diode on the back of the incoming power wire in the harness, they separated the leads, but have not replaced the diode yet. The seat now works, but we're wondering wether to replace that diode, or what to do next.

Just a reminder. This is a relatively unmolested ZR-1 that I've had for over twenty years with no real electrical problems or modifications to the electrics.

I'm totally clueless as to electrical aspects of the car, so on Monday, Dick, the mechanic that's working on it is going to sign up to this forum to talk direct to anyone that might steer him in the right direction.

BTW, could my car have caught the dreaded British electrical disease from some of it's Lotus designed components?:confused::icon_scra:mrgreen:

[Marc Haibeck]

Hi Bob,

The diode is there to attenuate voltage spikes that the motor sends out when it is turned off. The voltage spikes can cause erroneous operation of electronics in the car. The diode should be replaced. It's a common 1N4002 diode. It needs to be installed with the correct polarity. The diode should be available from a computer or appliance repair parts store.

[Bob Eyres]

Thanks Marc :handshak: We'll get a fresh one in there, and I'll post what happens.