Electrical - Headlight Gremlin / Alternator voltage too high??
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Joined: Sep 2011
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From: EVANSVILLE Wisconsin
Electrical - Headlight Gremlin / Alternator voltage too high??
This spring I upgraded my headlights and installed a relay / fuse set-up to keep the load off the headlight switch. Worked great all summer until the other night and while driving home I hit the high-beams and all the lights went out. Got back home and looked into it. The Fuse is very hot and tripping, and relays are getting very warm as well. If I switch the hi-beams off the lows' work fine, no issues. Also, I tested the lights this morning and they worked fine on high and low beam with essentially no heat build-up in fuse or relays. That is until I started the car and they immediately cut-out. I tested the battery with the car off and it's sitting at 13.6 volts and with it running at the alternator it's 16.2v. That seems high to me and perhaps that's causing the overheating of the fuse / relays? That said, I shut off the car, let everything cool off and tested again with the car off and the lights on high and they cut out again immediately, so not sure the seemingly high voltage is the issue. When I put in the relays I was extremely careful to solder all connections, heat shrink every splice, I have redundant very solid grounds, etc. Is it possible I have a bad fuse, bad relays, bad headlight? Would seem to me if any of those were bad they would either be stuck on, or not work at all.
UPDATE: Just tested the voltage at the hi-beam terminals and when the hi-beams are off there are still 6 volts running to the lights. When on high-beam it's the normal 12.5ish.. I believe there should be zero voltage at the high-beams when they are off. Is this correct? Thoughts?
UPDATE: Just tested the voltage at the hi-beam terminals and when the hi-beams are off there are still 6 volts running to the lights. When on high-beam it's the normal 12.5ish.. I believe there should be zero voltage at the high-beams when they are off. Is this correct? Thoughts?
Last edited by gbarmore; Oct 2, 2021 at 12:28 PM.
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Joined: Jun 2019
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From: Indiana
Huh..your 80 should be ok for power to headlights..what was the headlight upgrade?
most voltage i have seen / read that is normal for 79 anyway is 15.5 volts max.
i would also assume zero voltage to high beam when just low.
most voltage i have seen / read that is normal for 79 anyway is 15.5 volts max.
i would also assume zero voltage to high beam when just low.
Last edited by interpon; Oct 3, 2021 at 12:24 PM.
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I would try a new high beam relay first. getting 6 volts through the relay when it should be switched off doesn't sound correct.
Also, replace the voltage regulator in that Alternator. shouldn't be charging that high. 14.5 volts is normal.
Also, replace the voltage regulator in that Alternator. shouldn't be charging that high. 14.5 volts is normal.
Last edited by 4-vettes; Oct 2, 2021 at 05:47 PM.
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Joined: Nov 2016
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From: Southern MD
Your battery sitting at 13.6 volts is indicating that you are over charging due to high voltage. Fix the issue with the voltage regulator/ alternator so it puts out between 13.5 to 14.6 volts. Voltage = Current times resistance. If voltage goes up to 16.1 then the current is going up with it. The increase in current then creates lots of heat.
