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oil light always on 79 242

The engine does have oil pressure doesn't it? :-P

Disconnect the wire from the OP sender and see if the light is still on.
 
If I remember correctly, the light is on, even with the key off. So, there's something in the circuit that's feeding power to the oil pressure light directly from the battery.

-J
 
The wire to the OP sender is right next to the alternator wires. Are you sure they are all on the correct spot? Is the alt charging? Since the wires are new, I will not suggest that a bare hot wire is touching a bare OP wire.

Fake edit: or, maybe more likely, that a ground is touching the OP wire.


If I remember correctly, the light is on, even with the key off. So, there's something in the circuit that's feeding power to the oil pressure light directly from the battery.
Click to expand...
 
John242Ti said:
If I remember correctly, the light is on, even with the key off. So, there's something in the circuit that's feeding power to the oil pressure light directly from the battery.

-J
Click to expand...

The one scenario I know of that could cause this is a leaky or shorted power diode on the positive array in the alternator. With key in pocket, remove the D+ wire from the alt. If the oil light goes out, pull the alternator.
 
cleanflametrap said:
The one scenario I know of that could cause this is a leaky or shorted power diode on the positive array in the alternator. With key in pocket, remove the D+ wire from the alt. If the oil light goes out, pull the alternator.
Click to expand...

Thanks for everyone's replies.

So I unplugged the exciter wire to the alt (Nippon Denso 100A) and the oil lights stays off. When the exciter wire is plugged in, the light will now stay on only when the key is out of the car.

Alternator is charging, but the battery seems to have a parasitic drain somewhere. Battery was fully charged one day, then the next morning, completely flat.

I was going to replace the battery grounds and cable to starter since they are circa '79 as well.
 
Ohh okay. I gotcha.

Well if it makes a difference this has meant to be pertaining to the AMP light. :facepalm:

Exciter wire unplugged and it is ok, plugged it the light stays on without key in ignition.

I am going to replace the diode for good measure. Phil is helping me out with the part sourcing for a rectifier
 
wait a second... the Lamp light was always on and then you replaced the harness and the alternator and it's still on?

Also Chrysler Jeep and Ram use the same Denso small case as Volvo, the brushes and regulator are a little different but the rectifier is the same.

IMG_5538.jpg
 
philski o'flood said:
wait a second... the Lamp light was always on and then you replaced the harness and the alternator and it's still on?

Also Chrysler Jeep and Ram use the same Denso small case as Volvo, the brushes and regulator are a little different but the rectifier is the same.

IMG_5538.jpg
Click to expand...

The AMP light was illuminated with the key out, NOT BEFORE HARNESS REPLACEMENT. Things seems ok with old harness, but the plugs for IAC, CSI etc were beyond their lives. But the car kept randomly dying on me. So I sought to replace the harness with a brand new Volvo part.

But to be fair, iirc, the exciter wire was either unplugged or broken and not working properly before alt and harness replacement.

carver said:
15A write up with parts source.
Click to expand...

Awesome thanks very much!! Looks like I'm going to replace some parts in the denso
 
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