Author Topic: Alternator overheating and not enough voltage  (Read 1431 times)

Offline 1980ChevyK10

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Alternator overheating and not enough voltage
« on: March 05, 2017, 10:54:52 PM »
I've been burning up alternators like crazy on my '80 k10. Gone through 6 in the past 2 months and they're all getting really hot to the point I can't touch it. One even started smoking like crazy. First 3 were cheapy orielly best tests, then some higher dollar reman ultimas and now i just toasted a Brand new ultima. I'm guessing i have a short somewhere but I can't find where. I replaced my battery cables and made sure i had clean connections and took my starter out and cleaned it. Every ground i can find I've cleaned up and can't seem to get an alternator to last more than 3 weeks. When it happens my voltage drops and I smell hot electrical and boom another one gone. Would going to a single wire help something? Should I check my sense wire? What about a voltage regulator? I have a little thing that looks like a relay attached in my front fender with 4 wire going into it and one of them is broken the plastic off. I don't know what is is though so i can't get a new one. My battery's only about a year old and all the cells are fine. Anybody have any suggestion on what wires to check? Or maybe what alternator to get? I'm at a loss here. Thanks.

Offline Irish_Alley

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Re: Alternator overheating and not enough voltage
« Reply #1 on: March 09, 2017, 08:55:28 AM »
is there something in common as to when the alternators fry? like raining, snow or night time? how many wires do you have hooked up to the alternator?
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Online bd

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Re: Alternator overheating and not enough voltage
« Reply #2 on: March 09, 2017, 11:25:34 PM »
Welcome to the site!

Here's the relevant information...

'80 k10
  • [Alternator is] getting really hot to the point I can't touch it. One even started smoking like crazy.
  • I'm guessing i have a short somewhere but I can't find where.
  • I replaced my battery cables and made sure i had clean connections and took my starter out and cleaned it.  Every ground i can find I've cleaned up.
  • When it happens my voltage drops and I smell hot electrical.
  • I have a little thing that looks like a relay attached in my front fender with 4 wire going into it and one of them is broken the plastic off.  I don't know what it is.
  • My battery's only about a year old and all the cells are fine.

How intermittent are the symptoms?  As Irish_Alley asked, is there any recognizable pattern as to when the symptoms occur?

Things you can do at home (don't shortcut or make any assumptions):  Measure voltage at the #2 regulator (sense) terminal - it should measure constant B+ and match the voltage measured at the output post of the alternator.  How does the output voltage at the alternator compare to the measured voltage at the battery with the engine running at ~2,000 RPM, using the same ground connection for both measurements?  Connect the voltmeter negative lead to the battery positive post and the positive lead to the alternator output post with the engine at 2,000 RPM - what is the voltage reading?  Connect the voltmeter positive lead to the battery negative post and the positive lead to the alternator case with the engine running at 2, 000 RPM - what is the voltage reading?  Physically trace the charge lead from the alternator all the way back to the battery, inspecting closely for chafes and damaged insulation, especially around the back of the engine where the wire is hidden and where the positive battery cable crosses over the frame at the right front of the engine.  Take a close look at the wires as they pass through the short steel conduit at the right rear corner of the engine next to the exhaust.  Does the wiring show any evidence of heat stress such as brittle, discolored or distorted insulation?  Repeat the process with the #2 regulator terminal sensing wire - where does the opposite end of the sensing wire connect?  Check the three fusible links at the firewall junction block and the starter.  Post a pic of the "relay with four wires."

Things to have performed by a professional:  Have the battery properly load tested and a standard charging system test performed.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)