shiftngo

Attempted to fix the hacked up wiring on my 87' 305 IROC. An electrician got a hold of it and had wire nuts everywhere. Noticed that upon running the car for a little while that the fans weren't comming on. Relay is brand new. Hooked 12v straight throught to them off the load side of the relay connector and they came on. My buddy put a "Power Probe" on it and applied 12v through it and they came on for a second and then popped the simulated fuse inside the probe (don't know what amperage). Doesnt make sense that it doesn't blow the fuse on the car but does on his Power Probe. What amperage do the dual fans draw? Can these be safely switched manually? Do both fans even come off of the relay? I need some direction here, please help.

shiftngo

The previous owner seems to have attempted to bypass the fan relay and I thought I tied everything back in. Upon further inspection through the forums, I have come to realize that there is a second relay for one of the fans. Where is this relay located? The one I changed was by the battery.

shiftngo

Does anyone know what this is? It's laying behind the AC compressor.

Joemagjr

That looks like an AC compressor connector

shiftngo

But there is already one plugged into it. This is in the same loom as it though.

383RAT

I guess the electrician may have left the old one laying in bundle??? There is no other place on TPI car that I can think of for that connector.
I got the 89 service manual the wiring is pretty close to the same for 87. I'm doing this from memory.
The fans on your TPI car one is switched by ECU that runs thru relay. Your second fan is activated at a slightly higher temperature by a thermostatic switch in your engine block on the passenger side. This switch goes to a relay also. There is another temperature sensor 1 wire on your drivers side you undo that one you will loose your gauge reading. I think both your fan relays should be in the back driver side corner on firewall. The relays are on a bracket. On that bracket There should be 3 relays. 2 relays are identical. 1 relay that looks different is hidden behind the matching relays that one is the heating wire in your MAF sensor. On that bracket the Electronic Spark Control is there also. The two relays that look identical are the fan relays.
Some people disconnect the relay coil wires on the thermostatic switched fan and tie them into the ECU switched relay for various reasons.

Ozz1967

iTrader: (4)

That is the AC compressor connector.


You also have a fan relay just to the right of the brake booster on the firewall. There are two relays there that look identical. One is for the fuel pump, one is for the fans.

Question, do your fans come on when you turn the AC on? They're supposed to.

shiftngo

I don't see how this can be for the compressor. There is already one 1 plugged in. But no, fans don't come on when A/C is turned on.

shiftngo

After some more investigating, I have found were both relays used to be. I have one male connector left that I have wired back in and connected to new relay, assuming for primary fan. The secondary fan has everything removed for it. No connector and no relay. Should I just control secondary by switch? Primary still don't work BTW

Ozz1967

iTrader: (4)

The secondary is supposed to be run by the switch but don't run both, the wiring can't handle the amp draw of both fans. One fan will keep it cool for the most part, it won't overheat just from normal driving, it's how I've been running mine for the past 4 months. Just don't run the AC or you will run it into the red.

shiftngo

What's the best way of going about a manual switch for it. I've heard people doing it to a relay, but obviously I don't have relay for it. Just run 10g wire to the switch and back to fan fused at what 30A?

Ozz1967

iTrader: (4)

I personally wouldn't do a manual switch, I know I would forget to turn it on.

I would either contact Formula1LE here on the site and have him build you a superb stand alone harness that ignores all factory wiring, or I would do something like this...

Painless AC Activated Cooling Fan Relay

Which is also a stand alone harness and bypasses the factory wiring.

formula1LE

iTrader: (3)

If you are running two fans and would like a more modern 2-speed setup, I can build a specific harness for you which does not need to rely on the ecm. IMO, at the time GM thought designing the dual fan setup to have them kick on independently may have seemed like a good idea, but you get much more efficient cooling (with less amp draw) having both fans spinning @ 9V which effectively gives you a low speed/high speed feature. The shroud design really lacks airflow as well-a good upgrade is to swap the stock fan motors out for 1993-97 LT1 fan motors-these are more powerful and can be wired in 2-speed operation or, using one of my conversion harnesses, can also be wired as a 3-speed operation as well. I've worked with several members on their cooling systems-if you need any help feel free to PM me.