marv h.

One day I took off driving, got about a mile, and the GEN lite came on. I popped the hood and the alternater was hot. I felt it and as soon as my hand touched it, it burned me. It was way hot. It was so hot the insulation on the copper wire inside was melted, and dripping off. I shut it off, and when I started it up again, The GEN lite was not on. I drove it about a mile again and the GEN lite comes on. This happens every time. So I put a new alternater on. Now, the GEN lite doesn't come on any more. That is good, but now when I start it, the gauge ( I don't know if it is an amp or volt gauge) is down around 12 volts mabee, but after it runs for half a minute or a minute, the meter goes up over 14 to what I am guessing is somthing like 17. I drove it for a while thinking it may eventualy go back down, but it didn't. So what do you think? I am afraid it may be the regulator, and I know thats not good. If anyone can shed any lite on this I shure would appreciate any help I can get. Thanks Marv.

patdaly

14 is normal, at least on mine.

marv h.

Yes, 14 wouldn't worry me too much, but it is higher than that. I am afraid it may cook the new alternater, or something else bad. If it is overcharging, would the GEN lite come on?

vzdude

You need to get a volt meter. Double check the actual volts , then go from there. Maybe have Autozone or someone do a system check for you. They usually do it for free. It the voltage is too high, have them check your computer for codes. The voltage regulator is in the computer. If it is having problems , it should leave a code. Only other thing could be a wiring problem. If the field wire is grounded, it will make the alternator put out full voltage!

Dartmouth 12V

I agree that the next step would be a volt meter. If you are putting out more than 14.4 volts(the actual number is battery type dependant), you will ruin your batteries.

It sounds like a voltage regulation problem with the ecm to me. I can't remember off the top of my head what the easiest way to check it is but it can be done with a multimeter.

Hercules

I noticed you said your gauge reads around 12 volts at start up then goes up to 14 volts after a minute or so. Something you may want to concider is the pre-heater in the intake(the reason for the wait to start light). When I start mine, the pre-heater will cycle for several seconds a couple times causing the voltage to drop to 12 volts each time then return to 14-15 volts with each pre-heater on/off cycle. I've never watched how many times it does it based on the temp that I'm starting in, so, I can't say it should cycle "x" amount of times. With that said, I'm wondering if yours isn't cycling but sticking on or something along those lines. Those pre-heaters draw a lot of energy and I am guessing that's probably why they cycle so as to not damage wires or other componenets. Just something I'd look at since you mentioned the 12 volts at start up then the return to 14+ volts.

marv h.

Ok, Thank You guys for the replies and Ideas. I will see if I can check the charge voltage at the batteries. Thanks, Herc, I can see a definate drop on the gauge when the heaters cycle. Whether it is up around 17 or down around 12, it does its normal drop during the cycle. I am going to go work on it today.

marv h.

measured voltage at batteries, at 14.24, so I am thinking that is ok. If some one knows of a reason this is not ok, I sure would like to hear from you. Thanks to all who replied to help. Marv

Dartmouth 12V

14.2 is a good voltage to be seeing during charging of your batteries. Was your dash gauge still reading 17 when this happened? Also, did it take a while to come up to the 14.2(taking into account the grid heaters) like you were worried about before? I am just curious as to whether your gauge is acting up or whether you had a problem that has at least temporarily gone away.

marv h.

Well Dartmouth, my dash gauge is reading somewhere just over 14, I may have guessed it a little high at 17, I am not sure I understand the spacing and how the different numbers fall in there on the gauge. It is inside the range that looks like it would be normal on a temp or other gauge. The one thing I don't understand, is when I first start it, it is lower I think my dad said it was around 11. Then after about 15 seconds it moves up over 14. And whether it is around 11, or 14, I can see it drop slightly when the heaters cycle. They were only on for 2 or 3 seconds when they were cycling. I don't know. Marv.

Dartmouth 12V

It sounds to me like it is working from what you are describing. If you are seeing 14.2 volts at the batteries, then you are charging them.

I don't know why it takes some charging systems so long to start charging and others start right away. I had an alternator die on my truck and the new one that I put in would do exactly what you are describing with waiting several seconds. Over time, the delay time has decreased until it only takes a second or two now.

Hercules

Dartmouth raises a good point about differences from alternator to alternator. Sometimes the size of the pulley is slightly different on the replacement, which is why I've started swapping out the pulley when I have to replace an alternator. I had a Ram with a 360 in that I replaced the alternator. At idle, the power would drop to almost 12 volts. Problem was the wrong size pulley on the alternator. Replacing the pulley fixed the problem. Sometimes, if it's not the original from Chrysler, GM, Ford, etc it just doesn't work right. The alternator in our Olds Bravada has to be an original/from GM part or it simply just doesn't work in this truck. I don't know why. You'd think a rebuilt unit from any parts store would work, but, I've yet to find one that does. Got so fed up with it after trying two alternators from two parts stores, that I went to the GM dealer and got one and have never had a problem since.

marv h.

Thanks for all the help everyone. Knocking on wood, Marv.