Hey folks, as in the subject, I can't get my radiator fan to turn on for mt 85 TA (350 SBC). I built the thing top to bottom, so most everything is new. The fan is OEM, purchased from a member on here, and seems to work just fine. I bought an aftermarket relay circuit, so I did some troubleshooting, but cannot figure out the issue.

Some history about what I've done:
Originally, I wired up the fan relay kit and fan as in the instructions. Power wire from the battery to a supplied breaker, then to the relay, the opposing side to the fan, a ground to the relay, and a signal wire to the supplied temp switch, which I mounted in the coolant passageway next to the thermostat housing. When I grounded out the switch wire, the fan turned on correctly, but the switch wouldn't activate until 230 degrees (found out accidentally the hard way) which is just way too hot. Especially for a switch rated to 185 degrees, supposedly. Thinking it was aftermarket junk, I replaced it with one from the parts store, and it has not helped. The fan won't come on automatically (I've only tried running the car up to 220 degrees, so I can't confirm it doesn't come on at 230). Wondering if there was an issue with cleanliness of the system, or with the thermostat, I did 5 flush cycles with a garden hose, running it, filling it, draining, repeat. After refilling the system, and replacing the thermostat with a 160 degree thermostat, still no change. I checked the continuity of the switch casing to the intake, it is continuous, so the switch is not failing to ground out on its threads. When I ground out the switch wire with a cold engine, the fan turns on until I release the ground, as it should. When the engine is hot, the fan stays on, and does not turn off.

Any ideas what could be the issue? It seems like an issue with the temperature feedback, but I can't understand why a temp switch installed right next to the thermostat would give the relay poor feedback. In any case, thank you for reading my novel.

 

Is the problem "won't turn on", or "don't like the temp it actually turns on at"?

230°ish is the factory setting for the fan. Works great. Perfectly acceptable. Nothing wrong with it. Everybody (almost) seems to freak out over it, not sure why. If it works reliably at that temp, then ... it works reliably; and it's not "broken" or anything.

Different years and models of these cars use different inputs to control the fans. Some use the coolant temp, some the AC high-side pressure, some a combination of the 2. Most use the switch only for the secondary fan, and that only as a backup for when sitting still.

I think you would be best served by putting a stock temp thermostat back in it (190 - 195°), the stock fan switch, and just make sure it works like it's supposed to when it's supposed to. Some "improvements" people like to make ... just ... aren't.

There are "adjustable" aftermarket controllers that you stick the probe in the hot side of the radiator, if you're looking for something less reliable than the stock design.

 

I originally freaked out over the 230 degree "on" temperature as I was told by an experienced friend that 230 was an unacceptably high temperature, but thank you for letting me know that it is normal. Regardless of the acceptable temperature, though, if I bought a 185 degree switch, and it doesn't come on until 230, I think I am still chasing a problem. I really would like peace of mind that my cooling system is surely functional. Do you have a part number for the original temp switch? I am happy to install one, and as long as it turns on when it's supposed to, I will feel confident.

 

Pretty sure at AZ it's SW500. They have a couple that are for different cars in our year range, don't know the differences among them.

My car is a 83 L69 Z28. In maybe 87 or 88 I put a 400 in it. It has the single electric fan. The only things that turn it on, is the switch, and a ground from the AC system when the compressor was called for. (much cruder than some of the later variations) It would sit parked, in the deep South, idling; the temp would climb, and hit 230°ish; the fan would come on and run for a few minutes; the temp would drop to 210 or so; the fan would shut off; the temp would climb; and so forth. It would do that for an hour or more if I let it. If the AC was on the fan would run more or less constantly and the temp would stabilize at around 225 or so, just shy of where the switch would turn it on. On the highway it would run 200 - 205°.

I think your car is similar to mine in that regard but I'm not sure. The Firebird AC system controls were slightly different from the Camaro and there may be more parts than mine.

 

Awesome, thanks Sofa. i'll get the correct temp switch and re-check the operation of the system. Now that I'm less shy of hitting the 230 mark, I can really troubleshoot with more confidence.

 

I have an 84, my system runs identical to how Sofa's runs in his 83. They should be the same in the 85 as well. Let us know what you find out.

 

Hey guys, actually did some work on this yesterday. I reinstalled the fan switch I had the first time around into the thermostat housing. It turns on at 230, off at 210 so I'm fine with that knowing what I know now. Still seems odd that the switch is rated to turn on at 185, but if it consistently gives me 230, I'll take it. Thanks for the info and follow up guys