multi speed wiring fan problem

[atl]

so i have a 1999 motor, harness, pcm. and have two electric fans that i just wired up, and am have some problems with.



this car has air conditioning as well.

Im using a three relay harness that i put together, using this diagram:


I am letting the pcm, tell the relays when to go from high speed to low speed and vis-versa.

these are the pin points that i used on the back of the pcm.
blue connector pin # 42 for low speed, and red connector pin #33 for the high speed.

so this is whats happening, 1) fans don't turn on by themselves(i need to unplug and re-plug them) and even when unplug and replugging only one fan will turn on. 2)fans don't turn off. 3)the one fan only runs on high

I also found this other 3 relay diagram, difference that i can see is where relay 3 and 2 ground.


where should i start looking to find the problem?

[84TXGN]

I would guess you have something wired incorrectly. Double check everything. Also, using that system the fans are run in series (6 volts) for low speed so make sure the fans you have are able to do that. I know some aftermarket fans wont work correctly on low voltage.

[sccacuda]

I'm only seeing the left fan turned on for low speed, but it's not wired right. Looks like the motor ground is running through relay #3, which appears to be wired normally open, but it then is pulling it's ground through the motor of the #2 fan, which is resistance in the ground circuit. When it switches to high, only the right fan will work. You don't need 3 relays, just wire up a simple 2 relay system that does a 6/12v change and hook up the high/low coil control accordingly, that way, both fans will work on high (12v) and low (6v).

[ccmc]

Use the first schematic for stock two speed ls1 style fans, fan one grounds through fan 2 when low and grounds directly for high.

I'm running a pair of ls1 fans with this wiring. If you have aftermarket 1 speed fans then just wire the low speed to turn on one fan and high to turn on both. But that is a different wiring schematic, this one runs them in series so low speed is 6 volts to each fan and high is 12 to each. You probably need 12 to one fan for low and 12 to both for high.

Rick