I am going to attach a letter my cousin wrote to me. I told him I would see what ideas you guys would have in regards to his problem. He is stationed in Italy with the Navy and is having problems with his 1980 TA. It has a big block chevy 402. auto trans. Pretty plain car. Thanks; Mike I have been mad at the Trans Am the past few weeks, I am having some kind of electrical problem which appears to be overpowering the alternator when the engine is running. I had this problem a few weeks ago, OK no big deal, I switched out alternators with the one Josh had given me, which he said was a new 100 amp one he got from Eric. But then I had the same problem!! So, I figured maybe the one Josh gave me had bad diodes so I ordered up another 80 amp one from Summit. It worked great for a couple days then I had the same problem again!! So this time I took it down to the shop on base, they charged me $30 to hook it up to their stupid computer and then gave me back a paper saying, "Bad diodes, need a new alternator!!" I suppose it is possible to have 2 bad "new" alternators in a row, but I don't think likely. I think maybe they are full of crap and the alternators aren't really bad, but something in the car is just drawing mucho amps, maybe a bad ground or something. If you have any suggestions I am all ears!!! But right now I am thinking of ordering up a new high-capacity alternator, like 120 amp, because I am thinking that maybe after installing the new stereo and whatnot it is putting more of a strain on these alternators than they can take. So what do you think?
Some input might help. It is possible that the battery is drawing current and not charging. This can be caused by a shorted plate, typically caused by battery age. No alternator, regardless of its quality, will tolerate operating at full capacity for any extended length of time. It is also possible that the alternator was rebuilt with low quality diodes, which can happen, especially with after market conversions to higher capacities. Typically, any device pulling that amopunt of current will create smoke, burned wiring, or a blown fuse. Check the battery, with a battery charger, attempting to charge it that way. If it draws more than 40 amps for more than two hours, I suspect it is the problem. A battery capable of cranking an engine should not draw that kind of current unless it is internally defective. Ray
Alternator problem. Thanks for the help I sent the reply to him. If anyone else has ideas it would be greatly appreciated. Mike
More info on the problem. Here is some more info on my cousins car. I hope it helps in determining the problem. Thanks; Mike Mike, This was a good reply. About the battery not charging--like he said the battery is the first suspect. I bought a new battery right away actually because I thought for sure that's what it was. Then I had the old battery tested and it was good! And I have since had the same problem with either battery installed. I am now suspecting that it IS the diodes in the alternator like this guy said. That's what the shop told me when they hooked it up to their computer. But like I said, I have had the same problem now with 2 fresh alternators. Which means that I have had two bad rebuilt alternators in a row which sounds unlikely to say the least. One thing he said was very interesting though. He said that if something is drawing major current it will smoke or burn up wiring: I don't know if it is coincidental but around the same time I started having charging problems I almost had a fire under my hood, because the in-line fuse to my electric fans literally melted!!! I didn't think much of it, I cut the fuse out and ran the straight wires to the fans, then it worked fine. (One is a 10" and the other is a 16", both aftermarket.) But I have had this same setup for over a year now. I wonder if it is possible for my fan circuit to suddenly be drawing mad power for some reason? If so, did it maybe fry the diodes in my new alternator already? I hate to install another fresh alternator and burn it up too, if that's what is happening. Maybe you could do me the favor of posting this and see if anyone has any more ideas. Thanks; Paul S. -U.S. Navy- "Italy"
As a point of interest here; an electric motor draws its maximum current at turn on, and the current draw diminishes as the motor reaches its operating speed. If something is impeding the motor's attaining its normal speed, it will draw a lot of current. If most of the driving you do is of the low speed variety, or of short trips, the battery may never recover from the draw, maximizing the current drawn from the alternator. Ray
How much current are the fans supposed to draw? The mega-powerful Lincoln Mark VII fan draws over 100 amps on startup. It should, since it moves over 3500 cfm of air. To isolate a current draw problem, you can start pulling fuses from the fuse block and watch and see if the problem goes away. If you have access to an ammeter, you can put it inline and monitor current draw. Add back fuses until the problem reapperars.
Ttt Thanks for the input. I am sure it will be helpful. Keep the ideas coming if you got them. Sorry I don't have much more info for ya guys. I attached a pic. of the TA. It's the black car with the air cleaner sticking out the hood. (For those that are wondering what a "TA" is.) Heehe! He has a cowl hood now and added gold accents like the Smokie & Bandit TA. Mike
If the car keeps cooking alternators, there is most likely another issue and changing the alternator will be fixing a symptom rather than the problem. How are the fans wired? They should get power from the battery through a relay, if you attempt to use existing wiring you can expect a fire soon. Use the car's wiring only for the control side of the relay. I would have a good look at the ground cable to the block, and the ground connection from the block to the vehicle's chassis. If you have a bad connection, the alternator itself will be responsible for all power and any high load inrush current such as the fans turning on will overload it. If the inrush current on the fans is too high, an inline capacitor may help reduce the load on the vehicle's electrical system. PM me if you need any more specifics, or have questions.
Some thing else to consider along the same line as the fixing symptoms is the possibility that the fire has caused a problem causing the alternator's output to be shorted to ground, even intermittently. This can damage an alternator since there is nothing controlling the alternator's output current. On a generator, the output current had to be controlled to prevent the generator from burning up. Alternators are different. They typically can handle intermittently high currents without damage, therefore, the output voltage is the only controlled entity. Ford units are notorious for intermittent or defective grounding, even from the factory. Two ideas at which to look. Ray
Howdy could the fan motor bearings be shot/bad causing the fans not to run at full speed making them overload?
ok I forwarded the suggestions to him. He is very thankful for the help. I will let you know how and what it is when fixed. Thanks; Mike
