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<E24> Re: electrical bugs

> From: Andre Grandi <agrandi@domain.elided>
> Date: Tue, 24 Sep 1996 23:19:46 -0500 (CDT)
> Subject: <E24> electrical bugs
> 
> Digesters,
> 	My 83 633 has some strange eletrical problems, what else is new!
> 
> 	With the headlights on low beam the high beams come on halfway. I 
> measured about 6 volts on left high and 5 on right high. The left lights 
> are brighter than the right side. Also the fog lights come on without the 
> fog light switch on. And last but not least the high beam indicator on 
> the instrument cluster is half on when the low beams are on. Full on when 
> I turn the fog lights on.
> 	Now when I turn on the high beams all the lights go out! Even the 
> fog lights. Somewhere in the circuit I am getting some current source 
> with the lowbeams on.  Is it a relay that is N.O. but somehow makes some 
> contact? I swapped them out but to no avail.
> 	I have replaced the turn signal switch high beam switch and that 
> did not help. Anyway the turn signal was broken so it did cure that.
> 	Next I opened the headlight switch. Both of the diodes were 
> fried(1N 4004) so I replaced them with 1N 4004 Zn(could be zener?). That 
> was the closest part I had around. Cleaned up the circuit board and the 
> contacts. Reassemlbed it, and tried it out. Did not fix anything.
> 	BTW I have Hella low beam lights with 100/80 bulbs for my low 
> beam and a 6month old 80amp alternator. I have checked my body grounds to 
> the battery  and the engine. No luck. This problem has been here at least 
> 6 months and I guess now is the time to fix it.
> 

This is almost certainly a bad ground wire. Check where the headlight wire
attaches to ground on the car. I suspect it is loose or disconnected.

What happens is that the high and low beams effectively get tied in series since
their ground isn't connected. It is probably completing the circuit to ground
through the fog lamp circuit (since it is designed to shut off with the high
beams). That is why all the lights are on.

Now, turning on the high beams disable the fogs (it is the law in most states),
and you no longer have ANY circuit to ground, so all the lights go out.


- --
Russ Poffenberger               Engineering Specialist
Schlumberger Technologies ATE   DOMAIN: poffen@domain.elided
1601 Technology Drive		CIS:	72401,276
San Jose, Ca. 95110             Voice: (408)437-5254  FAX: (408)437-5246