The car is a 1991 Z28 305 TPI 5-spd. Quick history: Secondary fan ran constantly for several months. So in 4/2006 I replaced the A/C pressure switch and fan switch + connector (it fell apart in my hand). This seemed to solve the issue, and fan ran with A/C on. Then it stopped running and I replaced the fan motor with one from TPI parts. Then primary fan didn't come on and so I replaced both relays and everything was working fine, UNTIL I decide to install a manual fan switch. I wanted to hook it up to my secondary fan since it has a new fan motor and doesn't come on nearly as much as the primary. So I print off one of the articles from the forums and go to work. I thought if I back probed the fan relay and ground it, I could test it without spicing into the wire. I first back probed the primary fan relay (green & white) wire and turn ignition on and fan comes on, sweet. So then I go after the secondary fan, I back probe what I thought was the grey wire (its still the original harness so the colors aren't as clear) and nothing happens, so then I back probed the other wire (which turns out to be the brown wire) and nothing happens. So I retest the primary, and nothing happens - GREAT. I think I fried the relay. I get a new relay and still nothing happens. So I should have checked the fuses first. I found that the fan fuse under the dash for the is burnt, I replace it (20 amps) and run the car, the primary fan is working again. OK, back in business. At least I thought, but the secondary fan still doesn't come on, here are the tests I run:
1) Run car until it heats up to @228 (or close) and primary fan comes on - OK
2) Let the car cool down until primary shuts off, then turn on MAX A/C - primary fan comes on, but secondary does not.
3) I tested secondary fan motor by putting 12V to it directly and the fan turnson.
4) I switch the fan relays (I know the primary fan relay is working, so I swapped them) - secondary still doesn't come on.

So is there another fuse somewhere just for the secondary fan? I don't see it the diagram. I know its not the relay. I pretty sure its not the A/C pressure switch. Could I have fried the wiring harness when I grounded the brown wire (it doesn't look fried)? Could I have screwed up the connector when I back probed it?
Any ideas on where to look? When I tried to ground the secondary (grey wire) with a known working relay, still nothing happened, could I have fried the fan switch? Sorry for the long post.

VA1991Z28

 

Check the fusible link for the secondary fan. It is possible that you burnt it up. If that is the case, you need to buy a new one and run it inline with the 16GA red wire. It is hot at all times, so be sure to disconnect the battery.

 

weezul, thanks for the reply. Where would I look for the fusible link for the secondary fan? I don't see any other fuses in the diagram. Are you saying the connectors that plug into the fan? Back track those?

 

If I'm not mistaken, look near the battery. There should be a cable running from the battery that mounts near the radiator on the passenger side of the car. Attatched to that cable, there should be a bunch of other smaller (14-16GA) cables that supply various things throughout your car with power. One of those should be the constant power for your fan and there is a fusible link somewhere in line with that wire. Check that out.

 

Thanks, I'll check that out.

 

I found fusible link D (that's what the manual calls it) and it looks ok, how do I test it to be sure? It hs two red wires going in and a red & black/brown coming out.

 

Does this help?

https://www.thirdgen.org/forums/cool...-diagrams.html

 

Thanks for the link.