motor dogs when electric fan kicks on at idle

[buickpower]

When idling warm, the electric fan kicks on and causes the motor to dog a bit, it doesn't stall but the rpm drop is noticeable. I am not exactly sure what the fan came off (some gm car), but i used the fan kit from casper's. I am getting a solid 14volts from the alternator which is brand new. Any ideas on how to fix?

 

[85HOT-T]

try hi amp alternator. Fan may be using up too much.

 

[Benched]

If you have the Caspers fan relay kit you must have an 86-87 ECM. Correct?
I am not sure where the Caspers kit splices in, but I wonder if the voltage to the ECM or the voltage to the injectors is getting dragged down when the fan kicks in.
Load test your charging system at idle to make sure the alternator can handle the load, and test the amps going to the fan to see if it is getting to high. (A fuse should be protecting the fan)
Also a scan tool should tell you the voltage at the ECM, a voltmeter will tell you the voltage at the injectors.

 

[TurboDave]

It's not the voltage being dragged down. It's actually the extra heavy draw on the alternator. Takes a few more ponies to turn the drag, hence the rpm drop.

 

[85HOT-T]

Is it a dual fan or a single fan? I still think it is just pulling too many amps off you alternator. Load test the alternator and check how many amps the fan is pulling. Thats my only advice right now. Oh It could be bad wires too.

 

[buickpower]

yes, i have the 87 ecm and it is a single fan. Which wires are you referring to that could go bad? This was supposed to be a heavy duty alternator but i bet its not, will have to recheck the test sheet if I can find it.