'87 Truck Alternator question

[2wheelbob]

Just a quick question to make sure I haven't missed anything. I have a 1987 truck with the 22r engine and my charge and brake lights started staying on after starting my truck. I put a volt meter on the battery and am getting 12.07 vdc with engine running and above idle. With the engine off, I'm getting 12.11 vdc. If my auto shop teacher was correct, this indicates a no charge condition and a bad alternator. I called NAPA and they have the alt. in stock. Before I pull/replace mine, has anyone seen this before and found it wasn't the alternator? I'm just trying to cover my bases before stroking the check. Thanks in advance!

peace,
Bob

 

[cruiser88]

testing the battery is right but only half of it.

start it again and test the wire (the big one) on the back of the alt.

 

[2ndGenToyotaFan]

Yes, check the voltage at the back of the alt, but if it's still not showing anything above 12.1, then you probably don't need a new alt, you need new brushes for the alt. They are about $5. DO NOT TRADE IN YOUR STOCK NIPPONDENSO ALTERNATOR!!!! There is a reason that a replacement alt is $50 and a new one from Toyota is $400 See link...

https://forum.ih8mud.com/79-95-toyota-truck-tech/191784-alternator-brush-change.html

 

[Jonathan_Ferguson]

I currently have my Alternator torn down, what is interesting is that my charge and brake lights didn't do anything funny. The only issues I found are that the Brushes were very mucky and are near worn out of spec at 7.5mm compared to the minimum length of 5.5mm, the only other issue but not relevent in your case is that my Vacuum Pump Blades were slightly chipped.

I did do significant wire testing prior to removal, here are my results.