Alternator Testing

Here's a quick test to see if your alternator’s diodes are ok. I wish I could remember where I found it.

An alternator produces three phase AC current which is fed to a rectifier system of (usually) 6 diodes. This turns the AC into DC with just a small amount of ripple in it. The battery acts kind of like a filter so that this ripple doesn't affect anything. If one or more of the diodes fail, that small ripple will become much bigger.

With the motor running, turn on everything you possibly can in the truck. AC, high beams, radio, emergency flashers, all of it.

Here is how to check your alternator with a good digital multimeter. Set the meter to the lowest AC Voltage range (Yes, AC). Put the black lead on the negative battery post and the red lead on the positive battery post. Run the engine at about 1500 RPM.

You should not read more 0.09 volts AC. If you do, you must rebuild or replace the alternator.

I hope this helps someone.

 

Gonna try this in a minute....I have been having problems with my alternator

 

Let me and everyone on here know what results you get.

 

That test only for ac noise or leakage.You can have an alternator that will fail that test but produce the design amperage.

 

I tried 2 different meters.....one was 0.00....the other flashes 88.2 and 0

 

That's right. This is in no way a comprehensive alternator test. My understanding is that it only checks for a diode fault.

I put this out as a tool that might be an easy go/no go check. If you find this condition, you know you have a faulty alternator.

Unfortunately, if this test is within specifications, you may still have a bad alternator.

 

I like this...

https://itstillruns.com/test-alternator-field-current-7815682.html

 

I like it too!

I've never seen or heard of this, but it makes sense.

We now have another tool in the thread.

 

I'll try that too in the morning. My problem is while in drive with headlights and everything on my voltage is 12.8-13.2. Goes to 13.9 with headlights off and everything else on. Been chasing this crap for 2 years....about to order another alternator. I have a 130 installed that I bought from bamatoy off of here. He doesn't have any ideas. I tested all my grounds with volt meter and using techniques I found off you tube. Battery is 3 months old and load tests fine.

 

It took awhile to find this, but this may be handy for those that are comfortable rebuilding an alternator.

This company sells rebuild kits for alternators and I came across them while I was on the Ford Ranger Forum.

I have not researched if they have Taco repair kits. I've only been an owner of mine for five weeks.

Anyhow, here is a link to the company that sells "Victory Lap" brand rebuild kits. They were extremely nice when I called about a Ranger rebuild kit.

http://www.cpidivisions.com/products/parts-division-2/