Parasitic Drain Head Lights

khan.cross · Feb 15, 2026

Hi Folks,

I found a parasitic drain headlight related. When I pull the fuse, the drain will go.

I have already unplugged the headlight switch and relay but the drain remain. Any suggestions where the error is?

Some footage from a video I made

cobrajeff96 · Feb 15, 2026

Is that just a voltage indicator light probe or an actual multimeter? You can't do a proper drain test without a multimeter (ideally one with auto-ranging). There will always be a small amount of draw, especially with any OEM anti-theft like PATS. I forget the acceptable drain value but I think maybe it's around 20 milliamps (0.02 A).

ttocs · Feb 15, 2026

you said you disconnected the switch which would take out the only thing I can think of is the dimmer is staying on but low enough to not be seen. After the switch it does go through the multifunction switch(bright selector/turn signal) and it is possible that maybe it is doing something strange there, try disconnecting it.

The only other thing I can think of in that area that could be on the same circuit was years ago I found that there was a cruise control module/amplifier or something I think it was mounted down by the fuse box that for some reason was keeping my brake lights from getting above 9v. With it disconnected they were fine, with it being in the same location it might be on the same circuit....

khan.cross · Feb 28, 2026

I was on the hunt today again but could not find anything. Disattached the multi functional switch from the steering column and also the rear window defrost switch.

The Multimeter shows 0.60-0.70. However I wonder if these are milliamps, my multimeter display is 0.00 on 10A mode.
When I disattach the aftermarked android radio, the scale drops down to 0.25.

I think I will leave it for now, I got tired of this

cobrajeff96 · Feb 28, 2026

0.60 is 600 milliamps which is definitely way too much of a draw. I think your aftermarket radio is partly to blame since you're seeing something more lower after you isolate it (0.25A or 250milliamps) but even then this might still be too much. There could be something else also contributing to the unacceptable drain.

ttocs · Feb 28, 2026

I am surprised the deck is drawing that much power and he is right that is way to high of a draw.

you have not by chance installed any relays in the car over the years? I have traced more than a few current draws to a sticky relay installed and forgot about years ago that keeps the coil energized when it should not. It is not a huge draw but just enough over time to take out a battery.

khan.cross · Feb 28, 2026

ttocs said:
The only other thing I can think of in that area that could be on the same circuit was years ago I found that there was a cruise control module/amplifier or something I think it was mounted down by the fuse box that for some reason was keeping my brake lights from getting above 9v. With it disconnected they were fine, with it being in the same location it might be on the same circuit....

Previous owners disattached the cruise control from the throttle body. The switches on the steering wheel are also not working by plugs removed. I could remove the whole cruise control system to avoid any parasitic draw. I believe the cruise control module on my 97 is behind the fender driver side. Can I unplug it and remove it with the whole wiring? Maybe then there is no power going through anymore and I will have one reason less. And is there any module more? What about the one behind the fuse box under the dash?

ttocs · Feb 28, 2026

removing the cable would make the system not work at all, but that module could still be plugged in. it was a white box next to the fuse box with I think 2 harnesses going to it.

cobrajeff96 · Feb 28, 2026

Careful....because one of those modules by the fuse box could be a PATS module. It's the one that's super hard to remove because it has a plastic coated metal bracket surrounding it (for good reason).

khan.cross · Feb 28, 2026

Ok questions:

My GT was messed up from previous owners anyway. So I think to remove:

1. FOB keyless entry module and harness (because I have an aftermarket installed) which is in the trunk.
2. Cruise control module and harnes, this is behind the fuse box under the dash.
3. Air bag module (Air bags also not working on my car). This module is behind the middle console I guess.

So I can remove them all inclusive harness and the car will still work as usual right?

ttocs · Feb 28, 2026

I thought the inspections in europe were fairly robust? If so I would check that disabling the airbags if they are working or not will not cause problems. I don't think removing/disconnecting those things will cause a problem although I wasn't aware the keyless was aftermarket. There is a chance that there could be a starter kill but it isn't all that likely. If it does you will know it because turn the key and nothing will happen. Then it is just finding the relay normally under the dash and removing it and reconnecting the starter wire

cobrajeff96 · Feb 28, 2026

Not sure honestly. PATS is integrated with the things needed to start the car when you twist the key.

khan.cross · Mar 3, 2026

Do you think if the door open switches are not attached by unplugged sockets, this can drain battery?

cobrajeff96 · Mar 3, 2026

Probably not. They are +12vdc triggers for the PATS box in the driver's side trunk area to turn on overhead lights and sound the horn alarm if the doors were still locked when they were opened. Someone would have to purposefully remove those connections and the only way to do it is to remove the entire dashboard from the car.

khan.cross · Mar 3, 2026

cobrajeff96 said:
Probably not. They are +12vdc triggers for the PATS box in the driver's side trunk area to turn on overhead lights and sound the horn alarm if the doors were still locked when they were opened. Someone would have to purposefully remove those connections and the only way to do it is to remove the entire dashboard from the car.

Both door switches broke and caused this chime bell noise. So I unplugged the connectors, they are still in there. I am asking because the underhood fuse HD LPS also controls the door switches which is called courtesy lights.

ttocs · Mar 3, 2026

it is possible they are hooked up but unless the overhead light is on all the time I would not think they are causing a drain.

Any chance anyone has done any wiring back behind the dash and maybe there is a relay left in there? Were there any extra switches when you got the car? It is possible that someone tied into that orange/black wire behind the dash for a relay or to power something else

khan.cross · Mar 3, 2026

ttocs said:
it is possible they are hooked up but unless the overhead light is on all the time I would not think they are causing a drain.

Any chance anyone has done any wiring back behind the dash and maybe there is a relay left in there? Were there any extra switches when you got the car? It is possible that someone tied into that orange/black wire behind the dash for a relay or to power something else

I could not find any relays, also no switches under the dash. But it is a good point to look for. It is a convertible and the overhead lights are usual at the mirror. This mirror is not OEM anymore and does not have overhead lights.

ttocs · Mar 3, 2026

do you know where the power wires are for the lights in the mirror? If so dig that harness out and with the doors closed see if there is any voltage on it. It is possible the switch is bad and that is maybe keeping a relay in the system open somewhere to power the lights and while you do not have the voltage draw from the lights, the relay stuck on will slowly kill a battery(been there done that).

khan.cross · Mar 3, 2026

There is a plug under the plastic trim at the top of the windscreen. It is unplugged, I can trace that wiring too. Will give update on this.

Regarding the drain if my aftermarket stereo, I have read that these android radios stay in stand by and drain all the time. It has not option to disable standby. Need to put a switch to turn the radio on of by my self.

I am only hunting for the HD LPS fuse drain now.

cobrajeff96 · Mar 3, 2026

If the door switches were removed from the car, there is nothing to trigger the PATS module to tell it to activate any courtesy lamps. Unless that module is way more intelligent in its programming (but for a 90s car I doubt that). If there are no lamps in an aftermarket lamp, there is no current draw occurring so that part is irrelevant. It sounds like that Android radio should be on a relay tied to 'hot in run/hot in start'. And quite possibly there is active draw from some other source that a previous owner hacked into.