i have 89 iroc 350TPI
i am fixing previous owners fan wiring.. imagine that.. haha
anyway, i replaced the temp sensor for ECM (it wasn't working), i wired it back the factory way and i am about to install a low temp fan switch (200/185), i have a 170 GM thermostat.

my question is:

i want both fans to come on at the same time, so i plan to connect a jumper from the the green wire of 2ndary fan relay to the primary relay so the both come on with the low temp switch... however with the CTS still plugged in to give temp info to ECM, what do i do with the now unused green/white wire from ECM to primary relay? can i just cap it off? will it effect anything?

Also, now the fan comes on at 220 like it should but won't shut off with both relays green wires together, until i shut car off. my relays are very hot, i am thinking they are stuck closed when hot? new relay(s)?

thanks!

 

Its unlikely you will burn out one relay, let alone two at the same time

Sounds like you've got something wired wrong

Use this diagram


The C100 pin is for the fan fuse on 90-92 cars. Your 89 will have it at the C207 pin D (brn/wht)

It is fused 12v IGN for the circuit

The PCM wires are the ground side call. Run them to your ECM, thermo switch in the cyl head and or manual toggle switch. Since its a ground side, you can run as many conditions as you want. So set the ECM to turn on at X temp, thermo switch set for Y temp and manual ovveride if you see it creep past Z temp

 

thanks for the reply. it was wired properly, no wires are spliced they were jsut put back to their original positions in the harness. my 2 oranges are fused battery power, tan/wht IGN power, BLK/RED fan power, 1 GRN/WHT ground from ECM and other from fan switch.
the primary actually works how it should, comes on at 220 and shuts off when it should;
just when i connect the 2 pcm grounds of the relays together, they will both come on at 220 with the ECM but then not shut off.
however the 2ndary fan switch is still connected, i am now thinking when that switch grounds that it sticks, causing both fans to stay on...
we will see what happens when i change the switch.
then they will come on before the ECM commands anyway... and the ECM grounding at 220 will turn the fans on if the fan switch fails in the future.

 

does anyone know if there is a problem running the 2 fan relays grounds to the same fan switch. in other words, if i put in the jet 60600 200/185 fan switch and run the wire to both relays, what would be the problem? it's just a ground completing the circuit, right? besides they would come on/off before the ECM would even think of grounding the fan...

 

I actually have it wired like the 2nd one, dual fans controlled at 1 ECM pin.. except 1 side goes to the ECM pin and the other to the fan switch with the horizontal splice in there to activate them at same time.

 

Would work fine. The call side of the relays draw practically no power. Running 10 relays on the switch would still work

Using the ECM in conjunction with the thermo switch would just use whichever commanded ground first. If the ECM is set lower than the switch, it will turn the fans on at that temp, if the thermo switch is lower, it will call them on at its preset temp. If one fails (unlikely) the other will take up the slack

 

here is how i have it wired up. everything is as factory except for MY SPLICED IN WIRE.

 

See previous

 

ok so in therory if this is fine, why then do the fans stay on constantly after the are commanded on by the ECM? that's the overall question. is it my fan switch, relays or ECM? remember only happens when wired this way with the splice...

also, this is WAY easier than running a fan controller and all that like in the tech articles. so is there an up/down side to either way?

thanks

 

Sticking relay or the 12v fuse isnt wired on the IGN side