Weird issues with charging system.

[boostdtalon]

I have had a few issues that have had me stumped on what is going on with the truck.

First is with the equalizer on you can hear audible whine coming through the speakers that go up and down with the engine rpms. It comes and goes it seems. Some days I won't hear it and others it's loud. Still cant figure out if it's affected by the weather.

Second I had an issue with my power tonight. Upon initial start voltage read above 13V but below the third mark for the gauge. Once I started driving my voltage dropped down to around 9 volts and stayed that way for a few miles. Once I got back on level ground (uphill climb going home) I noticed the voltage returned back to what I normally see and stayed that way till i got into the parking lot. Then it dropped down a to under 13V until I put it in park.

Come tomorrow I will put my mulitmeter on it and see if the battery is the issue. If not than I will go and get it tested.

Battery and alternator were replaced within the last few months. Alternator was a autozone refurb.

 

[chengny]

Maybe try some resistor type spark plugs to quiet the RFI (radio frequency interference).

You don't still have points in your distributor do you? I thought 1975 was the last year for breaker type ignition systems but I am not sure. Too large of a point gap will produce RFI.

But when you report a flucuating charge rate - I start to think arcing at the alternator brush/slip rings.

The gap in the connection creates arcs. The arcing rate tracks along with engine/alternator speed. This would also explain why your voltage seems to fluctuate with the position of the truck - as the gap open and closes.

These are just basic things to check out - I'm not that familiar with 81 and older trucks.

 

[72chevy2door]

if it's an aftermarket stereo or aftermarket speakers it could be because someone ran the 12v wire too close to the speaker wires. Newer aftermarket stereos are more sensitive to the "road noise" or the "whine". Such as if someone put an amp with subwoofers in their vehicle and ran the RCA wires with the remote turn on wire it can cause the same thing. The voltage changing like that could be the battery is getting a dead cell in it, or quite possibly bad grounds. I would check all grounds make sure they are clean and tight and then check the battery hot that leads to the starter.

 

[boostdtalon]

if it's an aftermarket stereo or aftermarket speakers it could be because someone ran the 12v wire too close to the speaker wires. Newer aftermarket stereos are more sensitive to the "road noise" or the "whine". Such as if someone put an amp with subwoofers in their vehicle and ran the RCA wires with the remote turn on wire it can cause the same thing. The voltage changing like that could be the battery is getting a dead cell in it, or quite possibly bad grounds. I would check all grounds make sure they are clean and tight and then check the battery hot that leads to the starter.

Well the stereo system was installed sometime in the 1980's.So I'm going to update it speakers and wiring very soon.

I was solve part of the issue. Seems the crush washer that was on the bolt for alternator had failed and caused the belt to lose tension. New crush washer and flat washer and it's fixed. battery voltage was at 13V.

 

[72chevy2door]

Congrats on getting the voltage problem fixed Now for the stereo "whine" that you have it could be that the head unit is just simply worn out. I had a old head unit do that. Was the damnedest thing cause I figured it was the wiring but I replaced head unit and it was all fixed. But if you do plan to install new speakers with head unit and you decide to run new speaker wire make sure speaker wire runs by itself. You could even put it in wire loom(not sure if it will make a difference in anything) or if you put an amp in it run RCA wires seperate from ALL other wires or you can pick up interference (whine or road noise) Just what I learned in doing stereos in my personal and friends vehicles

 

[boostdtalon]

Yes that is the plan. I have a new head unit, but still need speakers and will definitely be updating the wiring when I do. Most of the speakers are blown and feel it'll be for the best to do a update to the wiring.

 

[72chevy2door]

That's understandable. If I remember correctly the dash speakers are 3 1/2" and the rear speakers on all trucks and suburbans are 4x8 or something like that. There is a thread on this forum that says what they are. It's in the stereo section. Is what I plan on doing to my suburban is adding two additional speakers to the center of the dash. Factory had an option for them that's why it's cut out in the metal framing but I've yet to see a truck factory equipped yet. They will be the same size speakers as the outer ones. I'll just run one speaker off the left side of the dash and the other one off the right side of the dash. I've done it before in my brothers suburban and boy that helped big time with the highs. He also had two 12" P3 fosgates in the back so bass was over bearing to the highs. Just figured I'd let you know in case you may want to do that route also.

 

[boostdtalon]

My speakers were swapped at some point with a alpine set in the doors and some kind of house speaker behind the seats. Finally ordered the replacements on Thursday. Figured out the audio buzz is from a failing equalizer. Looks like I'm without a stereo till I get it all swapped in

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