I replaced my alternator and the new one seems to be coming and going..

When working I'm reading 14 V on the two leads and when not, I'm reading battery voltage on both leads.. Usually around 12.4 or so....

The tach lead reads 8 volts no matter what...

How does the tach lead work the tach ? Is it frequency and not voltage ?

When I first start the truck the tach doesn't work but there's still 8V on the connection at the alternator... Then after a bit it kicks in... But then it goes away and that's when the voltage drops back to battery voltage.. But the 8V is still at the tach lead....

Any troubleshooting suggestions before I take this alternator back ?

The "Battery" light comes on when the key is in position 2.. It never comes on when things are acting up...

I just don't know what to think...

Thanks

John

 

Take it back. High failure rate on rebuilds offered via big box chains. It is an AC signal from alternator to tach, which counts the pulses. Rebuilders are forced by bloodthirsty beancounterz to use the cheapest parts, and China does not have great quality control. Once they master that, no manufacturing job is safe.

 

This is a new alternator I got at a local alternator shop... He ordered it in...

Today we went for a breakfast run and it worked fine... But the tach still was in and out a couple of times... I think the tach issue is separate from the alternator...

I spun the crap out of it this morning... You should have seen all the junk come flying out of the tailpipe...

Hasn't really acted up since then... Still breaking in the brushes maybe ?

I'll probably call the alternator guy tomorrow and see what he thinks..

John

 

Where did he order it from?
If he did not rebuild it himself or its not brand new then its prob a mass rebuilt and is bad.
I went though 4 in 2 years before buying a brand new one off of e-bay for $150.

 

If the tach stops and the battery charge volts drop to just battery volts, the alternator brushes are not making constant contact. But whatever the case, it is not charging the battery (needs to be 13.8 - 14.4 when running at idle, nothing else on). So it should be in warranty.

 

Is there any thing else in the circuit that could cause this intermittent operation ? I don't want to take it back and just have it test good..

The fact that the charge indicator never comes on other than at startup just bothers me...


Guess I'll start it up and smack it with a rubber hammer and see it that wakes it up...

Gonna snow here this evening...

John

 

Going to snow...whatever.