Headlights come on spuriously

Son's car - 1998 Ford Contour SVT

Spuriously, and only during cold weather (~30F or colder), the low beam headlights come on. This is in the driveway, not while driving. (This car has separate bulbs for Low and High.) He can disconnect the battery or remove the low beam relay to get them to go off. Or sometimes if he leaves the headlight stem forward (Hi beam position), the lights do not come on.

The battery has been drained several times over the last 2 or 3 years. He has swapped relays around to try to get it to stop, but with no success.

Other pertinent (probably) information - about 4 years ago he had a front end collision that messed up the radiator, AC, sunroof, etc.

I suggested that cold weather also means salt and brine on the roads which could possibly be setting up an electrolytic situation leading to a short. (I have no idea if that could really happen.)

Any suggestions on how he can proceed with troubleshooting? He likely won't take it to a mechanic. Would a trained professional have any special tools or techniques that would help pinpoint the issue?

Thanks, Craig

Reply to
Williams
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Son's car - 1998 Ford Contour SVT

Spuriously, and only during cold weather (~30F or colder), the low beam headlights come on. This is in the driveway, not while driving. (This car has separate bulbs for Low and High.) He can disconnect the battery or remove the low beam relay to get them to go off. Or sometimes if he leaves the headlight stem forward (Hi beam position), the lights do not come on.

The battery has been drained several times over the last 2 or 3 years. He has swapped relays around to try to get it to stop, but with no success.

Other pertinent (probably) information - about 4 years ago he had a front end collision that messed up the radiator, AC, sunroof, etc.

I suggested that cold weather also means salt and brine on the roads which could possibly be setting up an electrolytic situation leading to a short. (I have no idea if that could really happen.)

Any suggestions on how he can proceed with troubleshooting? He likely won't take it to a mechanic. Would a trained professional have any special tools or techniques that would help pinpoint the issue?

Thanks, Craig

Reply to
Williams

Does the car have daytime running lights?

Reply to
Bill Vanek

Does the car have daytime running lights?

No, the car does not have daytime running lights.

Reply to
Williams

How often does it happen? Is it predictable at all, besides cold weather?

Reply to
Bill Vanek

Get the wiring diagram.

You now know the problem is before the relay. In older cars, all that comes before the relay is the headlight switch and the wiring.

My guess is that you have more than that between the headlight switch and the relay. My guess is that you probably have some solid state module.

This means your possible failures include that module going bad, and that small leakage voltages across the switch might trigger that module.

Get the wiring diagram and see first. There might be some other stuff that can trigger the headlights, like an alarm system. Those are possible failure points as well. The schematic will tell you.

--scott

Reply to
Scott Dorsey

How often does it happen? Is it predictable at all, besides cold weather?

No, it is not predictable. At least he has not noticed any particular pattern.

Reply to
Williams

If it has keyless entry also check the alarm relay. It is supposed to flash the low beams if triggered, could be it has a fault.

Reply to
Steve W.

As other have said, you're going to have a very hard time without the wiring diagram. One thing you can do is remove the relay, and check the voltage with a digital meter at each terminal in the connector with everything off. You can also check the resistance to ground in any terminal that has zero volts, but you should also check voltages with the lights turned on. Don't bother checking the resistance on any terminal that has voltage with the lights on. Anyway, record the readings you got with everything off, and next time you see the lights on, pull the relay out, and get new readings. Any reading that is different than normal will lead you to the problem, but again, it's hard without the wiring diagram.

One of the terminals is the ground circuit to turn the lights on. You can probe each terminal with the relay plugged in with a test light. If the lights turn on when you probe a terminal, that's the ground circuit to turn the lights on. This won't work, though, if your test light has high resistance. If you can see the wiring coming off that terminal, you can visually inspect for wires spliced into that circuit, or for areas where the wire might be rubbing against a body part.

Someone else mentioned that the car might have an electronic module controlling the lights. If it does, and it's cheap, that might be a good guess. If it's a wiring problem like an intermittent short to ground, the lights should flash on occasionally over bumps or on turns. You could try abusing the car at night in a parking lot with the lights off. It'll be easier to see if they're coming on.

Reply to
Bill Vanek

Looked at the schematic: This one is a simple circuit. Power switched through the relay. (not ground switched) Headlight switch, multifunction switch, out to a splice point where the alarm/keyless entry relay connects up. From there out to the low beam relay.

I would suspect either the keyless relay or the module controlling it.

Reply to
Steve W.

Craig

Reply to
Williams

Right - if it's power-switched, most of what I said is of no use. It's rare for a wire to short to power.

If it's necessary to guess, relays are cheap. I'd start with that, and then the module.

Reply to
Bill Vanek

The problem is between the light switch and the wiring to the relay. My guess is that it's the switch.

Reply to
dsi1

"Williams" wrote in news:DZgPs.102308$ snipped-for-privacy@newsfe02.iad:

"Spuriously"?

"Spurious" means "misleading" or "false".

I think you mean "sporadically", which means "randomly from time to time" or "intermittently".

Reply to
Tegger

schematic won't help much if there's an aftermarket alarm...

Reply to
jim beam

in electronics and engineering, it also means "not predicted" or "unexplained". "spurious emissions" are a concern in radio transmission for example, so in the above context, "spurious" is perfectly acceptable.

sporadic means they are within the normal operation, just of unpredictable occurrence. spurious means not inside normally expected operation, which in this case is more appropriate.

Reply to
jim beam

in electronics and engineering, it also means "not predicted" or "unexplained". "spurious emissions" are a concern in radio transmission for example, so in the above context, "spurious" is perfectly acceptable.

sporadic means they are within the normal operation, just of unpredictable occurrence. spurious means not inside normally expected operation, which in this case is more appropriate.

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Thanks for coming up with the definitions, Jim Beam. I was glad to see that I had not used the word "spuriously" in a spurious manner. Like most people, I sporadically use the incorrect word.

Craig

PS - The weather has warmed, so the headlight problem has not recurred. Troubleshooting has come to a standstill.

Reply to
Williams

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