Volvo RWD 140-160 Forum

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Amp Light on when car is not! 140-160

I've got a strange problem in my 72 142E, the explanation requires somewhat of a story so here I go. I bought a 72 142E less than a week ago now. On the test drive before I bought it nothing was wrong, the car ran and worked beautifully. I took the car home, changed the oil, and went out for a drive. Hours later when I was at my friends house the amp light came on, but not when you would expect like driving own the highway with every electrical accessory on full power, no no with the car parked, engine silent, and nothing turned on. This is strange my friends and I thought, so we disconnected and reconnected the battery until we detected a faint sound emitting from the voltage regulator. So hours later I drive the car home, pull the key out, and the light is now off. I'm thinking "yeah, Volvos fix themselves all the time." Maybe, but the next day the amp light is on very softly as I drive the car. Then later that day, driving home from a trip to Port Townsend in the dark, the amp light comes on very brightly and finally the battery dies on the side of the road. First I put in a new voltage regulator I have then I put in a new battery, the car starts up, we continue or journey home, but the amp light is still on and very bright. So the next day rolls along, I take my car and the alternator down to the car parts store, have the alternator tested, it fails to produce to charge, I install a new one. Great, the car is charging, the amp light is off when I drive around the block. Mission accomplished I think, nope, the amp light is back on when I turn the key to the off position and remove them from the ignition. So what is going on? I've replaced the alternator and voltage regulator and again he light is on when I park the car. Please help me.








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If you didn't have a good ground through the chassis to the engine and battery, you might have zapped the new alternator diodes.

The voltage regulators are specific to the type of alternator, I believe. The Haynes manual takes pains to treat each type (SEV-Marchal vs. Motorola, I believe) separately. You may have a mismatched setup, however, even at the discount store, the parts guy asked me which type I had.

Only other thing I can think of without tracing through the circuits is a shorting ignition switch.



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Check your ground between engine and body and battery and body.



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I second that!

http://www.brickboard.com/RWD/?id=650831



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Bad diodes in the alternator will do this. Often as a last step before failure.



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