alternator testing

[presterone]

I think my alternator is bad after rewiring the power cable to it(arced against metal housing) I can't find a wiring schematic. I traced the two white wires on the power stud of the salt and one looks like it goes to a 60 amp fuse in the engine bay fuse box and the other wire to the "alt relay" I'm wondering if I fried that relay but I'm not even sure why there is a relay for the alternator. Does the ecu control a ground to this relay to excite the alternator so it will charge? Also the relay is a three prong so how do I test it?

 

The old way to do it is to start the car remove the hot cable if it die,s then you got
your answer.Check and make sure you have 12 volts to it if you have a meter also
check output at idle.

 

[rdomeck]

Don't do what it says above. I know people do this and sometimes it works. The problem is that if your alternator is good it can go full charge and fry itself. Get a volt meter. There cheap and you can't trace down electrical problems without one. Charge your battery with a battery charger. If you don't have one and can get the car started, check the voltage. You should have 13.8 volts at idle. Anything below 13 and your not charging. Test this with all accessories off. You won't have 13.8 volts at idle with every single thing on that you can have on. Shut the car off and check voltage. It should read 12.5 after a good charge. Maybe a little higher.

I have used this method on old british cars on up to new Porsche's. The alternator went out last year on the VR4. Unfortunately it didn't light the idiot light and I didn't know it was bad until my battery run down in the middle of an intersection with one of my twins in the back seat.

Main thing is to check voltage with a decent volt meter and go from there!

 

[presterone]

Im a certified technician I know what an alternator should put out and how to use a voltmeter. I should have made my question more straight forward. I was hoping to figure this out without pulling the alternator and testing it, or towing my car to work to use the tester there. I was wondering why this relay only had three prongs and one goes to nothing. Why does it even have this relay? I've done voltage drop tests checked for blown fuses and charged the battery, its still at 11.5 volts at idle. I still can't find a good wiring diagram. Thanks for the replies though, hopefully get this bitch running and driving this weekend, dyno time scheduled next weekend.

 

[transparentdsm]

this happened to me, its the voltage regulator inside of the alt. in these cars, they just go bad. the way to solve it is you buy a new/remand saturn 110 amp alt(not sure the model number, do a google search cross-referencing dsm and saturn alt) and then make a custom shield that sits above it to prevent anything from falling on top from the P/S area and make sure you have a heat shield on your o2 housing and downpipe. the excess amount of heat from the o2 housing and downpipe can cause alt failure.

 

[presterone]

Thanks just pulled it and it failed the test. Also my water pump was leaking from where the alt bracket is bolted to the pump it was really loose. FML

 

[mikus]

sounds like you may already know, but the adjuster bracket bolt passes through coolant channel - tighten it back up and see where you stand

 

[presterone]

Man I hope so