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Headlight switch turns on oil light

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sweatlock View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2022 at 6:04am
Oil light comes on with headlights off, engine off, ignition switch on.” 

This is a normal condition, both the OIL light and the ALT light come on as a system/light bulb check when the ignition switch is turned on, engine not running. 

OIL light stays on regardless of High/Low beam switch position. 

Disconnecting the blue wire from the oil pressure sending switch, the OIL light goes out and the ALT light then flashes with the headlights on. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2022 at 7:00am
Go pac car? Sounds like ammeter gauge hook up is causing a ground loop, if go pac. Either the Go pac junction has something crossed, or voltage regulator could be cross wired with its connector. Like my checking with original and new harness connector for headlight switch.

You can test by disconnecting regulator connection, and do a short engine operation with headlights on to see if oil light activates. If not, the issue is around the areas I am starting to question. Alternator / Ammeter connections.

It is not uncommon to have a wire harness be assembled with a wire crossed. It happens time to time, with all custom kits, from computer to automotive. Few fully do an operational test, unless they have requirements to produce high volume with low error rates.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2022 at 9:18am
Hmm.  The fact that the oil light goes out when the engine is running tells me the wiring from the oil light bulb to the pressure switch is functioning correctly.  For the oil light to come on when the engine is not running, the oil light usually gets powered from the ignition switch feed.  If the light is coming on without the ignition feed but with the headlight switch pulled then I'm guessing it is being powered from something else in the headlight circuit.  I would have guessed that it was from the dash lighting circuit but your statement it only happens with the headlights and not the park lights still is confusing.  It would be interesting to see if the dash lights come on when the ignition is turned on (engine off) without the headlight switch being pulled.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2022 at 11:05am
Just for kicks, try your light switch with the dimmer switch full on and full off. See if the oil light changes in any way.
With the switch properly grounded, there has to be wires crossed or a circuit using the brake light to find a ground source.
You can take you voltage meter and check the brake light socket to find out which side is + when this happens. Guessing it's the wrong side of the circuit.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: May/25/2022 at 7:37pm
UPDATE:

Yes, this is a Rally Pac car. 

So I checked out the pinout on the headlight switch plug and compared it to the original and it matched. Did the same with the plug on the fuse block and the instrument cluster plug, no issues. 

Checked all of the grounds and pulled the blue wire off the oil pressure switch with the headlights on to see the headlights dimmed, thinking perhaps the circuit was trying to find a ground through the oil pressure switch - the headlights did not dim, no change. 

Since the only time the oil light came on was with the headlights on, not the parking lights, I disconnected both headlights since it was relatively easy to do - oil light still came on. 

There are two brown wires that go from the headlight switch to the dimmer switch and the headlight warning buzzer - I was going to disconnect the dimmer switch plug but the switch worked fine. However, I noticed that the headlight warning buzzer would come on briefly when the headlights were turned on and then would go off - it should have stayed on. I disconnected the white wire at the fuse block since it feeds both the emergency brake light and the other side of the headlight warning buzzer - no oil light with the headlights turned on! So I pulled out the headlight warning buzzer and that was the fix - why, I’m not sure, although there is what looks like a diode in there that could have gone bad. 






Edited by sweatlock - May/25/2022 at 7:39pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Jul/06/2022 at 3:54pm
You could pop open the warning buzzer and if there’s a diode in there you could meter it with an ohm meter on the Rx1 scale and see if it only passes continuity in one direction. If it shows continuity in both directions the it’s bad. If the diode is bad it can be replaced by a 1N4004 diode. A very common part. This would have been a Radio Shack type of item a couple of years back. An local tv repair or audio/car radio shop should have one on hand if they would be willing to sell or give you one. Just note that there is a stripe on one end and the replacement would go in the same oriention. I can’t imagine the diode would cost more than a buck or two.

Edited by george w - Jul/06/2022 at 3:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: Jul/06/2022 at 4:55pm
I will give it a try, thank you. 
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