Dual fan control on 8d
 

on a camaro running 8d can the ecm control both fans?
I know on 6E it doesn't so I wire both together usually or a manual fan switch for the second

we had some real hot weather lately and I noticed the second fan wasn't coming on, on a friend of mines car I had put a chip in(91 Z28) that was over heating, I thought could be a problem with the car, I checked the relay, jumped the signal wire to ground and the fan turned on
but I wasn't getting a signal from the ecm even thought the car had reached the requested temp,

is it something I'm doing or is the car,ecm or wiring at fault?

The ecm only controls one fan. Its the driver side I believe. Your other fan is controlled by a fan switch in the block and the a/c pressure. Turn the a/c on and see if the fan comes on. It should. The switch in the block should ground the relay around 240 degrees stock. Way too hot! You should check that to ground. I've had two of these go out on me.

why does 8d have 2 fan turn on temps then?

[QUOTE=89Vert]on a camaro running 8d can the ecm control both fans?

Yes... you just have to swap pins(wires)at the back of the ecm. And then you can set both temps. Do a search on it...glenn is the one who told me about this and it works great.

The second fan status is just so the computer knows whether its on or off. It doesn't close the ground for the fan to come on.

I would have thought the ECM can override the switch? I guess not then.

Would it be easier just to hook up fan relays for both fans and have the ECM control both relays at the same time through the wire that gets grounded by the ECM to activate relays.

Something as illustrated. So you would have 2 relays controlling each individual fan. And tap into the wire that runs from the ECM to the relay coil and plug that into your other relay. So when the ECM operates one fan the other one gets turned on too.

This should work without any problems right?

THe numbers along the relay are the bosch 12volt relay standard numbers just to make connection easier.

I'm just going to splice into the wire that the ecm grounds to control the primary fan relay and hook it into the wire that controls the secondary fan relay,

on my car it has single fan and I spliced into the wire and ran a ground switch,
so i can manually run my fan or computer control

Yeah that would work too and might be easier too. I wonder why they set the car up like this.

Weird.

On the few 89-90 L98 car's i've owned, the relays were tied together from the factory, so both fans came on at the same time.

-- Joe

I did the same thing. I have a 383 HSR running SD (8D). I ran one wire from GE8 to the Green/White wire on the Fan Relay. Then I wired both fans to the relay. I believe it's better to run both fans, instead of one anyway.

on a hot day the single fan can't keep up if you put a lower thermostat and lower the fan turn on temp,

Maybe this will help, dual fan control like the vette.

https://www.thirdgen.org/forums/diy-...ht=fan+cooling

This is kinda how wired mine, except I think I put a diode in the wire from the high A/C switch to the relay and ran a new wire from the relay to F8 at the ECM, that way it dont turn the ecm into a latching relay and all orriginal swithes still work as a backup.IIRC

I also hooked toggle switches to ground the relays for manual control. I know, I'm a control freak.:D

Works good, HTH:thumbsup:

Awwwww yeah, like the vette.. ;)

-- Joe