Okay I have a light on. It dosen't usually stay on but it flickers on and off sometimes bright sometimes not so bright. It seems to do it more when I have just started the truck. I replaced the Alt only a year ago so I believe it to be good. I had the batteries test a month ago at a garage and they said that the batteries were good but they could tell that the batteries are old. What do you guys think is time to dump some money into new batteries or do I have another problem.

 

Sounds like your glow plugs are pulling a lot of power if it only happens when you first start it up.

 

How about the belt. Is it slipping? or old? I've seen this happen whne the belt had strecthed just far enough to slip when the alternatr was pulling a big load, but still OK and not making noise either. There is a set of marks on the tensioner arm that will show how far the belt has stretched.

You can lean on the belt with something when the light is on. If it's slipping the lite will go off. I use an old idler pulley I had laying aroung attached to a chunk of wood.

 

I wouldn't think it would be the belt. I replaced it just a month and half ago with the new gator goodyear belt, so I suppose it is still good.

 

If the belt is OK it may be a connection on the batts, alt, starter ect ect. or your batts are getting weak. Have you checked the voltage when the lite is on? and after the GP's are off?

 

Thats the question I really had. Is it more likely that its a loose connection or a bad batteries. I know that the major connections are tight (batt, Alt, starter). I guess that that could only mean the batteries have gone south.

 

Casey I would look closely at the small connectors on the Alt. they have been known to be an issue. the wires get rubbed or the connectors melt or get loose

 

Thanks for all the suggestions but nothing has worked yet. I looked at all the connections. I tested the GPR to see if it was pulling to much and its not. I dont know what to think. Do you guys have any other ideas? I guess I'm just left to think my batteries are done with.

 

Put a voltmeter on it before you start it then watch meter,you may have regulator going bad or just week.Reman alts depending on where rebuilt don't always last.

 

I agree with fuelman, if all of your connections are good, your batteries test O.K. (they passed the load test, "age does not matter") then you probably have a regulator with a bad or weak diode. Remember "NEW does not mean GOOD". I have put on new and/or rebuilt alternators that did not last a week.

Take your truck to a place that can test the charging system under a load. This should isolate the probelm. Good Luck.

 

I say go back to the three wire connector. Pull it, and remove the red lock, pull the pins out, clean them and squish them a little. I had the same problem. Light would flicker sometimes, but the gauge still showed charging. Take the connector apart and clean it, even if you think it's good. That's my bet.

 

Try rubber ducks idea 1st,and make sure that belt is clean, Because it does sound like a bad alt'reg but if thats been replaced the next best guess is connections.!!!!

 

Casey, I just checked your profile and you have a 96 ford. 95 -approx. 97 had a wire that would burn-out in the alt. and cause the flickering light you mentioned.Have it load tested, mine gave me grief for about 2 weeks until I tested it. This is a common problem with this alt.

 

This is the connection on the back of the alt right? I just wraped those wires in electrical tape to protect them, but it shouldn't be to hard to unplug it and clean it out.

I cant really bench test the alt because I dont have a autozone or checkers around here. Sometimes you just dont know what you have until you dont. I'm pretty sure that the alt is given me a good charge. The gauge says its good and the truck always fires right up, but I guess the regulator can still be bad. I'll try to clean that connection up first. I sure hope that does it. It went off completly for 20 minutes of driving today, but it came back on the next time I started it. I thought I had it fixed, until I went to leave again.

 

have you tried jump/starting/running it to see if it goes off?