I have a 1989 C1500 with a 350. The voltage will be erratic when motor goes above 1500 rpm when cold. After it warms up the voltage will become steady around 13.8 volts. At first startup it goes a little over 14 volts until the motor speeds up. When it idles back down the voltage rises back up. What could be the problem. I replace the wiring to the regulator plug and the output wire. Please help
Tim Slover
Ok Tim Here we go!!! It sounds as though without seeing the truck that the brushes are getting stuck. is there a lot of belt dust or oil on or around the alternator? If you have a low charge when cold,, it's a sign that your belt is slipping. Check that belt first. If there is oil on the Alternator, Replace that alternator and get rid of that oil leak. on the plug that goes into the alternator,, put some silicon sealer around the plug after you put the plug in. we have found that plug will vibrate and cause erratic charging problems too Later Tim PASCO, We are your charging and starting specialists
410-546-2041My 86 Jeep CJ7 with it's 'GM' AC Delco alternator just started doing the same thing again. I need a new fan belt again.
In my case it is always a belt getting shiny. They get polished up from mud (liquid sandpaper) and dust because I off road lots, then they start slipping under load when cold, then all the time. Mine just went to all the time because it is cold out....
I test mine by seeing if I can hand slip the alternator pulley on a cold off engine. If I can hand slip it, it will slip under load.
I have a V belt which is more prone to this, but a serpentine can also polish up.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > I have a 1989 C1500 with a 350. The voltage will be erratic when motor
Could be anything from bad brushes to cold solder joints in the regulator which become more solid when they heat up.
It may just be easier to swap the whole thing out.
--scott
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