Scratch your noggin with this one...

[Doober]

So I had an alternator die on me recently. Replaced it on Monday, and I've been having issues ever since. At first I fried a reman. alternator without even knowing it. The 2nd one I had a strong feeling something was wrong. I finally tracked it down to something with the electric fan circuit. It was wired as below, removed the temperature switch for simplicity (between the relay & the fan). The aqua lead is for turning the alternator 'on', and the circuit is ignition-switched. (newer style alternator)

My issue was I could leave terminals 85, 86, and 87a connected, but couldn't connect 30 (which ran directly to the BAT terminal on the alternator) until after I started the car, otherwise the alternator wouldn't start charging, and I believe that's what killed the two before. The current alternator is off my '91 Sonoma, which has 88,000 miles or so on it. 2 or 3 times so far I thought I fried it as well, but after a while it will start working again, like it's askin' for more punishment :roll: Anyway, I've removed the relay altogether now, just using a switch in case I have to turn it off. I took the car for a drive to warm it up and set the temp. switch just above the normal operating temperature. I drove it to work tonight without any trouble, and the fan never even kicked on 'cause it didn't get warm enough to (makes me happy there). Just wondering what everyone else's take is on this. The alternator that died to start with must've fried the regulator, because the voltmeter went extremely high before it died, and I'm wondering if it did something to the relay, because everything works fine otherwise.

 

[82elcamino]

sounds like your creating too much of a voltage spike directly at the regulator. you should be pulling positive lead from starter or battery for a fan on a relay.

 

[Doober]

Well, the kicker is I removed the relay altogether thinking that's what it might have been, and installed a toggle switch, running power to the battery post instead of the post on the alternator (battery post -> switch -> thermal switch -> fan). It worked fine for me heading to work and home that night, but it was dead once again in the morning. I've since disconnected it completely and though I don't currently have a clutch fan on at the moment, I also haven't had any more problems.

 

[82elcamino]

running the power straight thru a switch is no good. the switch itself isnt meant for that much amp draw. thats what the relay is for. that way the switch just has to do the job for the relay. the relay then feeds GOOD power and amperage to the fan. not sure what you meant by it was dead again? alternator?

if your running a temp switch, run a relay. painless wiring will have some type of diagram that is easy to follow.

or..run a clutch fan =)

 

[Doober]

The setup ran fine for me, the temp. switch was always there, and when I did have the toggle switch hooked up, it didn't draw enough current to cause the switch to get hot, even warm. Regardless of how that stuff was hooked up, it's disconnected, and I'll be running a clutch fan. Yes, I was talking about the alternator being dead again.