On my 81 dodge D150 truck when i have the headlights on they sometimes get bright then go dim and if i have the blower fan on it will increase the speed and then die down. They both do it at the same time. Also when the lights are on i dont have any low beams. I replaced the bulbs awhile ago and when i bought the truck the guy changed the dimmer switch to. I tested the switch and it works according to my voltage meter. I checked the wires and there is no shorts. So i was wondering if any one here knew what the problem is.

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Joe Reusch

1981 Dodge D-150 Slant Sickness

voltage regulator?

Yep, the surging voltage is likely a problem with the voltage regulator and/or alternator. The headlight problem is likely a faulty (open) connection between the high/low beam switch and the wiring harness, or in the low beam feed wire between the high/low beam switch and the headlights. You really need factory wiring diagrams to chase down faults like this; recommend you buy a factory service manual as soon as you can.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

When the lights are on they work fine with the high beams but as soon as you click the dimmer switch they just shut off. So i dont know if that would be an open circut. They worked fine until one day tehleft side just didnt come on one day so i replaced both of them and it never had lows since then.

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Joe Reusch

1981 Dodge D-150 Slant Sickness

Possible a bad ground or corroded terminals. Have you tried cleaning all connectors and grounds?

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Casually looking for a Clifford hyperpak intake for cheap.

Yes, it would be an open circuit somewhere between the dimmer switch and the low beam filaments, as I said. Go check it out.

It's not bad grounds; if it were that, the high beams wouldn't work. The low and high beams have a common ground path, but separate feed paths.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.