Flickering lights part 2!!!

[John G]

Ok, I tried everything mentioned. My 93 EB has flickering lights and a jumpy volt meter. It comes down after around 20 minutes but all the lights still flicker at idle. Here is what I did so far:
1. cleaned battery terminals and all connections on alternator.
2. added a ground wire from - side of battery to frame ground.
3. brought the truck to Autozone and they hooked it up to this fancy computer and both the alternator and regulator check out fine.
4. Any suggestions?? Please help. I can't imagine that all this flickering is not hurting something in the long term. Could it still be the alternator even though it checks out fine. I disconnected the multipin plug to the alternator while it was running and the flickering stopped although the voltmeter showed that the battery was discharging at the time.

 

[Alec]

If the problems stopped when you disconnected the alternator, then it's almost definately the alternator or regulator.

 

[John G]

I was thinking the same thing. The guy at Autozone told me that it checked out fine although the output voltage fluctuated a few times while at idle. At 2000rpm's it was as steady as could be.

 

[Alec]

Is the truck idling normally?

Alternators have been known to be bad even if they test ok. Is it possible the wiring from the alternator is bad, the actual wires?

 

[John G]

the truck idles and runs fine. I cleaned all the contacts on the wires that lead to the alternator. I don't think it is the wires. What good is that fancy computer at Autozone if it can't detect a faulty alternator. I think that the alternator is fine too. I am thinking that maybe one of the diodes in the regulator is bad. Maybe one of the alternator brushes is bad? The guy at autozone thought that maybe the serpentine belt was slipping but it is new and it doesn't appear to be slipping. If it was then it would probably make noise or at least the lights would flicker above idle. I guess I am gonna have to cough up the 150.00 and "try" a new alternator. It will really rot if after I install it the truck is still flickering. After all, electrical parts are not returnable. There is a $50.00 core charge also when I return the old alternator.

 

[dogfriend]

In the other thread, mrboyle said that he thought that it was one of the diodes in the alternator that was causing the flickering. Were they able to test for this at Autozone?

A diode is like a one way (check) valve for current. It seems like they would be able to check if this is the problem, but their test may only test output.

 

[John G]

He said that the machine also checked the diodes. He did say that the voltage fluctuated a few times while the test was performed but the machine gave the alternator a clean bill of health. He said it checks the diodes and the brushes. I am still thinking that it is the alternator. Maybe I should remove the alternator and completely clean everything and try reinstalling it. That would be a hassle though. He said that the voltage fluctuation during the test almost appeared like a slipping serpentine belt. It definately isn't slipping though. It is new.

 

[dogfriend]

Could it be a problem with the belt tensioner?

Its probably the alternator, but just thinking of other causes.

 

[TheRookie]

Go to some cheap parts store and buy a cheesy alternator on a credit card. DO NOT give them a core at that time. Put new alternator in. If this fixes it then go give the parts place your core to get a few bucks back. If it does not solve it then return it saying it is the wrong one. MAKE SURE to keep it clean so it looks new. Also Make sure to tell them it was the wrong one and NOT tell them you got it to test something.

 

[dogfriend]

Originally posted by TheRookie
Go to some cheap parts store and buy a cheesy alternator on a credit card. DO NOT give them a core at that time. Put new alternator in. If this fixes it then go give the parts place your core to get a few bucks back. If it does not solve it then return it saying it is the wrong one. MAKE SURE to keep it clean so it looks new. Also Make sure to tell them it was the wrong one and NOT tell them you got it to test something.

This is a good strategy, but....buy your rebuilt from a reputable parts place like Napa or similar. I have done the musical alternator thing before on a Toyota and it is easy to get a cheap one that won't work right. Don't always buy the cheapest part...it will cost you more time and money in the long run.

 

[smith60]

When a diode goes bad it will still put out the same voltage cheked by a multimeter, but if you were to hook up an oscilloscope you could detect a bad diode because your sine wave wouldnt be clean. The autozone puter probaly cant detect a bad diode.