Quick ? regarding replaced alternator

[gregory_gdp]

91 3.1L engine... I replaced a bad alternator this morning and went for a test drive. While on the test drive the CEL flashed on and the fan blower went from full blast to medium output when I let off the gas. When I gave it more gas the CEL lite went off and the blower fan went back to full blast. Did this off and on for the short little test drive that I did. Could this just be because the battery wasn't fully charged when I went for the test drive. Or did I get a bad alternator or could it be something totally unrelated.

[maxwedge]

Post the year and engine when starting a thread. The cel code would also help , I would suggest checking for good cable connections first, then check the alt output.

[gregory_gdp]

yeah forgot that. Also I don't have a code reader and I haven't been able to read the code yet from that jump the wire trick yet. Would using a paper clip work to jump it or do I need a special jumper wire?

[maxwedge]

Paper clip is ok.

[gregory_gdp]

So the CEL comes back with a code 35 which in the book says Idle Speed Error and tells me to replace the IAC. When the engine is running you can hear an audible clicking noise coming from that general direction so it could very well be a bad IAC (can you clean and reuse or does the clicking noise indicate a bad IAC)

When I drove the car home it seemed to do ok (minus the CEL lite) for most of the trip, towards the end it didn't want to idle right and when I did get it home and checked the battery it was pretty drained so I still could have issues with the alternator too.

[4x4 blazerguy]

You need to check the alt output, it should be 13.2 to 14 Volts. The IAC motor may need to be just cleaned. On autozone.com on their repair

info it gives you a diagram to check the IAC motor. But again you need a VOLT, OHM METER. So if your going to do any electrical work yourself you need a meter.

[gregory_gdp]

Cleaning the IAC seemed to do the trick runs a lot better, smoother and after finding some instruction on how to actually use a multimeter right (dad gave me an older analog one but forgot to tell me how to use the blasted thing) I tested the alternator and it was only putting out 12 volts and that's with everything turned off. Don't know if that makes a difference though. So I'll take it out anyway and run it to autozone to have them check it out for sure.

Thanks for the help guys.

[jeffcoslacker]

You should be showing 13.8-14.5v with everything shut off...12v running is not enough.

Check the wiring from the alt to the ECM and the charging wire's fusable link down near the starter for damage if the alt checks good on the bench...

[gregory_gdp]

Took the alternator in yesterday and it was indead DOA so replaced that and took it for a test drive and while the CEL didn't come on the Idle was going all over the place and would die at lights here and there. But it'll sit there and idle fine when you first start it and while driving it'll run fine as well. Just when your coming to a stop it'll go crazy for a bit and either die or go back to idling fine. So replaced the IAC this morning and took it for another drive but it does the same thing.

[jeffcoslacker]

Originally Posted by gregory_gdp

Took the alternator in yesterday and it was indead DOA so replaced that and took it for a test drive and while the CEL didn't come on the Idle was going all over the place and would die at lights here and there. But it'll sit there and idle fine when you first start it and while driving it'll run fine as well. Just when your coming to a stop it'll go crazy for a bit and either die or go back to idling fine. So replaced the IAC this morning and took it for another drive but it does the same thing.

Usually when you disconnect the battery long enough to change the alt you'll loose idle memory and they'll act like that. You can either drive it around anyway, and it will recover eventually, but with a lot of surging and stalling.

I park them with wheels chocked and parking brake on, start it, put it in gear, and let it sit and run in gear for about 15-20 minutes...when the fans turn on, it should have relearned it's correct idle strategy...

[gregory_gdp]

I don't exactly know what I did but what ever it was that I did it fixed the idle problem so the car runs and idles great now. Thanks again guys for all the help.