Electrical Gremlins - No Power

[Rep007]

Here is a strange occurence. Started car, cranked right up and idled fine. Turned on headlights and car died. No power to anything: starter, dash gauges, fuel pump, headlights etc. Battery is brand new and is indicated fully charged via charger. Even if battery was worn down due to a short, I would expect minimal juice to power gauges, turn signals, etc. Nothing. Any suggestions where to begin?

 

[Steve]

Battery should, if fully charged, be capable of providing enough to keep the engine running plus a few ancillaries, at least for a while, even if your alternator were fried. This one beats the heck out of me.

 

[90 XJ-S]

I suppose if there were a Direct short, through heavy gauge wire, in the headlight circuit.... That you could shunt enough power off to kill the engine.... But, I would expect two things:
1. Smoke...probably lots of it as something fried.
2. power to return when you turn the headlights off. (this of course if #1 didn't fry the primary circuits.

Seriously, I just had a thought... A serious ground could have caused a loose battery cable to go extremely high resistance and appear as an open.. Try twisting the clamps (and attachment point at the other end of the primary hot and ground cables). If they seem at all loose... First take them apart and clean them... then put them back together... tight.

And fix whatever is wrong with your headlight circuit before you turn it back on!!!

Mike

 

[RVMAN]

Is this a Healy with a Battery Cut off switch? If so , how does it check out? Good luck

 

[Rep007]

Strangeness continues...Managed to start car, still same occurence when turn on headlights, car dies. Turn ignition, no power. Car will re-start if I move negative battery cable. Filed down both cables (negative and positrve ground and tightened cables) same occrence when I turn on headlights upon idling. No smoke, burning smell as suggested, nor battery cutoff, just complete power loss. Has the prince of darkness invaded my car?

 

[bugimike]

What are we dealing with here in the way of switch? A faulty-worn out bug eye type combo switch could a) have the wires connected incorrectly to the terminals b)have worn internal contacts. a) would seem to just make everything die, while I would think that b) would create awful smells and smoke1

 

[SilentUnicorn]

sounds like some seriously Bad grounds. is the engine block grounded well? I have read (on this Forum) about cars that would not shut off if the headlites were on.



mark /ubbthreads/images/graemlins/driving.gif

 

[Biff]

As Bugimike suggested more info will be required for a better answer to your problem. What year/model are we looking at. Is it positive or negative ground? Generator or alternator? Any other mods? Does the car only shutoff with the headlights or when anything else is turned on? Basically, it sounds as if something between the ignition circuit and headlight circuits is shorting both out yet not blowing a fuse or smoking.

 

[Rep007]

Car is a 66 Midget, GAN3L42509. Positive ground. Generator, no mods, correct orginal 1098 engine. Typical 3 position MG headlight switch. Car only dies when headlight switch is moved. Wipers, heater, no effect on car. No smoke. No blown fuses. Will install a ne headlight switch and verify. Someone suggested examining the ground strap also.

 

[Steve]

Yes, the ground strap will be a useful thing to check. Make sure that the connections at each end are clean too.

 

[Rep007]

Replaced the ground groundstrap and and cleansed the contact areas. Car does not stall anymore when headlights activated. Afterwards, cleansed the headlight contacts at the swtich. Hopefully the ground strap which was slightly frayed and oil/roadgrime covered was the culprit...