Pulsing dash lights

[gtxdude]

Out the other evening for a cruise and turned my lights on and noticed that dash lights were pulsing. I very rarely have car out at night so lights are never on. I shut car off and lights quit pulsing, only when running. Alternator or voltage regulator maybe? doesn't seem to be affecting anything.

 

[Mopar Tim]

Voltage regulator. Make certain the regulator has exactly battery voltage. EXACTLY. no less....

 

[gtxdude]

Have a spare one in the trunk, we'll switch them out and see what happens. thank you

 

[toolmanmike]

Out the other evening for a cruise and turned my lights on and noticed that dash lights were pulsing. I very rarely have car out at night so lights are never on. I shut car off and lights quit pulsing, only when running. Alternator or voltage regulator maybe? doesn't seem to be affecting anything.

What year and model? Points or electronic regulator? Sounds like an old point type.

 

[gtxdude]

MSD in a 65 Dart, no ballist resistor. Electronic vr

 

[67Dart273]

This can be a form of voltage feedback due to poor grounding or harness voltage drop, so main causes are

Indeed, VR especially older mechanical regulator (69/ earlier)

The usual drop in the ignition circuit, bulkhead connector, ignition switch and connector etc

Or poor grounding at the VR to battery

Try making up a good big alligator clip lead with big say, no12 wire. First try clipping from battery POS direct to the junction that feeds the VR and ignition, and if no effect, jumper direct from battery NEG to the VR mount. AKA nearest bolt you can get to, and clean and re-tighten the VR mounting bolts, firewall, and rear of VR

 

[Dana67Dart]

Does this only happen at idle or at 2000 rpm as well?

Are your dash lights LED?

 

[gtxdude]

Both, sitting in garage and noticed it going down the road first

 

[Dana67Dart]

A bad diode in the alt can do that.

The diodes take the AC the alt makes and turns it to mostly DC.

If a diode or two are bad then more AC to the devices in the car.

Drive it to the local car parts store, they should have a alt tester that they can hook up on the car.

Cheap and easy test

 

[superchargeddrt]

Flickering lights are caused a lot of times from the ignition switch contacts being dirty or worn. I had the same problem with my car and I've fixed a few of my friends cars but feeding the wire that typically comes from the ignition switch to the regulator through a relay. I'll look for my schematic and post it here.

 

[scatpackbee]

A bad diode in the alt can do that.

The diodes take the AC the alt makes and turns it to mostly DC.

If a diode or two are bad then more AC to the devices in the car.

Drive it to the local car parts store, they should have a alt tester that they can hook up on the car.

Cheap and easy test

I had the same problem.

I changed the alternator and it went away.

It was a bad diode in the alternator.

 

[superchargeddrt]

Here's the schematic.

 

[fuzzman]

Here's the schematic.

View attachment 1716124987

Is there anything different you did besides this upgrade. Just curious if this solved your problem, I’m fighting the same issue
Pat Faley

 

[superchargeddrt]

Is there anything different you did besides this upgrade. Just curious if this solved your problem, I’m fighting the same issue
Pat Faley

No that is all you need to do. The flickering lights are caused by the dirty contacts in the ignition switch causing the the voltage on the blue wire (the i terminal in the regulator) to vary. The relay will assure a clean voltage supply to the regulator and will eliminate the flickering/pulsing lights. If you have any questions just PM me. I cleaned out my mailbox.

 

[67Dart273]

Here's the schematic.

View attachment 1716124987

I usually recommend that this added relay power the ENTIRE ignition run loads under the hood. This releives the switch of load, and insures good solid power to those loads. VR, field, ignition system, etc

In other words cut the blue coming out of the bulkhead, use the bulkhead end to trigger the relay, and connect the engine bay end to the switched contact.

 

[fuzzman]

Thanks for the reply I did do the relay trick noticed that the flickering stopped on the lights and the gauge slowed down on the weaving back and forth. I’m still waiting on a new ignition switch from rock auto and will give an update after I install it. I changed out the battery also today and noticed my negative cable end was loose and probably has been for awhile that should also help. Thanks again
Pat Faley

 

[superchargeddrt]

You're very welcome.

 

[superchargeddrt]

I usually recommend that this added relay power the ENTIRE ignition run loads under the hood. This releives the switch of load, and insures good solid power to those loads. VR, field, ignition system, etc

In other words cut the blue coming out of the bulkhead, use the bulkhead end to trigger the relay, and connect the engine bay end to the switched contact.

That's a very good idea.