Over the past few months I have noticed my voltage gauge dipping from 13 V down to 5 or 6, then back up. Usually it only lasts for a second or so. It got worse a month ago and the voltage would stay down, lights would dim, etc. I replaced the alternator, which included the voltage regulator. Then the gauge would start to dip down again from time to time. I noticed that the negative battery cable was almost rotten through so I replaced that, which seemed to make the gauge more stable. However the voltage reading still dips from time to time. Is this a bad gauge, bad wire, or something else? Battery voltage is around 13, and the battery is about a year old.

 

You might try checking the ground strap for the engine as well, since you found your battery ground to be corroded so bad. You might also want to check any other ground wires for the instrument cluster to make sure you are not getting an intermittent open circuit.

 

Thanks for the reply. Can you give me any detail on where the engine ground strap might be? I didn't look really close but I couldn't find anything that looked like one.

An update on the situation: After replacing the negative battery cable, the right front turn signal -- near the battery-- does not work. The right turn signal light on the dash stays on at all times. My fiancee followed me home today and said that the brake light on the same side was working only intermittently. The bulb is not bad on the turn signal. I assume both these lights to also be ground problems but don't know where to look. I also don't know much about how a negative battery cable is normally routed, but my old one was grounded in four places: the starter mounting bolt was the main connection, and then the cable was stripped in the middle and had two wires coming out of that, one to the frame and one to a connector back up near the battery. Finally, a lead came off the end near the battery and went to a ground bolt on the body right in front of the battery, near the grille. This wire also had a wire spliced off of that that looks like it was going to the right front headlight/signal cluster. I replaced all these in the same way that they were originally. I then took all the connectors back apart when the signal didn't work and tried to clean them and put some dielectric in them. Any ideas where to look for ground problems with these lights? Could they possibly be related to the voltage gauge problem as well? Any help would be greatly appreciated, I'm about at the end of my rope with this.

 

Forgot to mention that I changed the multi-function switch a year or so ago, don't think that's the problem. All of the lighting issues came about after messing with the ground cable.

 

Sorry, I have been away for awhile.

It sounds like you have an intermittent short somewhere in the wiring for that passenger side turn signal, but I am not clear on what you mean by the turn signal (I am trying not to sound dumb).

When you say that the turn signal is not working, do you mean it is not blinking, or do you mean the marker light is not working? Usually if the turn signal lamp on the dash stays on it means that one of the marker lights on that side has an open circuit (bulb does not burn), if the signal lamp flashes fast that usually means one of the signal lights has an open circuit (lamp does not blink).

Since you say the indicator lamp on the dash is staying on all the time, then we will assume that the problem is with the marker lamps on the passenger side, and let us step back to your original problem with the negative cable. It looks like the ground cable should have fixed the voltage problems you were seeing earlier, however, since you said the marker lamp in the rear works intermittently, you should assume that the lamp in the rear blinks out as your voltage gauge dips down. That leads me to think you need to trace the wiring for the passenger side marker lamps, starting with the one up front. Do you have a service manual for your truck? If not, PM me and I will scan on the one I have and send it to you.

Sorry for the long post!

 

Thanks for the input. I fixed the problem. It turns out there was a ground from the battery to the body near the headlight assembly that was bad. I cleaned it up and put it all back together and it was good to go. The turn signal was not flashing, but the indicator inside the truck was solid when the lights were on. I guess it was just a weird symptom of a bad ground. I also cleaned up all the connections on the alternator with electrical cleaner, and that took care of the voltage gauge problem. The brake light problem I think is separate; it appears to be something with the multi-function switch on the steering column which I've replaced before. Right now I can fix the brake light issue by jiggling the turn signal lever, but I'm sure eventually I will have th replace the switch again.

 

please help i have a 1985 ford truck the amp gauge is jumping at idle speed the engine up lights quit flickering and gauge is stable is it the alt ????