jay_blkz28

I have a 94 z28. My car runs cool when Im on the highway but when I get stuck in traffic or in stop and go traffic, it starts to get hot. The temp. guage almost gets into the red but it never does. I flushed the system and put a new thermostat in (180 degree). Never made a difference . The only way that I found to cool it down is to turn on the A/C. Last week when I got done washing my car, I started it and let it idle in my driveway. When it started to get hot, I noticed the fans were not on. It got up to about 210. Then I turned on my A/C and the fans came on high speed. It started to cool off the car. Then I turned off the A/C and the fans went to low speed.

Why don't fans come on automatically when the car starts to get hot? Is there a sensor that my be bad?

EDS01SS

iTrader: (30)

Sounds like the temp sending unit that controls the fans has gone bad.Im not sure which sensor it is off hand on the LT1s but im sure somebody will chime in.

jay_blkz28

Anyone have any suggestions??

Intragration

iTrader: (1)

Or maybe one of the fans is bad? I'm pretty sure with the LT1s (and maybe LS1s too) that one of the fans handles the cooling as necessary when the AC is not on, and the other fan is for ONLY when the AC is on...something like this. I would look at one of the FAQs, I think there's a good explaination somewhere about the roles of each of the fans. Either way, I think they're sequential, so when the AC is on, they're both supposed to be on...maybe? When the one fan is on, test to see if the other is getting voltage too.

jay_blkz28

I know that both of my fans come on when the a/c is on and I think both on are on after I shut it off but Ill check to make sure. It just that the fans never come on when the car starts to get hot. I have to turn on the a/c just for the fans to come on. My friends z28, i think his fans come on as soon as it gets hot. But thanks for the info. Ill check that stuff out to see if that's the problem.

98LS-WON

Check all of the connection to the fans, then test the fans. Just take them off and rig a hard wire to the battery to see if they actually spin, unless you know for sure that they both work then skip that part. If they work normally then it most likely the sensor that turn them on thats bad.

jkichline

iTrader: (1)

I fought my cooling system for years. That includes, thermostat replacement, water pump replacement, flushing/filling/bleeding several times, turning AC on to run cooler in traffic, and all kinds of other stuff. I'm not sure where I started noticing the fan operation. What I found out is that this behavior (hot in traffic/cool at speed) is somewhat normal. I never figured out EXACTLY how the fans are supposed to work. What I did was, I bought a hypertech power programmer (cheap off of ebay) that is designed to turn the fans on sooner. Also, I bought a 160° thermostat and put that in. I now run between 160° and 180° at all times. From stock, the fans turn on high at 235°F. That's a very high temperature in my opinion. I wish I knew the exact reason why GM chose these numbers. Here is a link that talks about this in detail.

LT1 Reverse Flow Cooling System

If you look at the F-Body section, it lists the fan operation. I copied and pasted them here:

Primary (LH) or Dual Low-speed Fan(s) ON: 108 C 226 F 248 psi*
Primary (LH) or Dual Low-speed Fan(s) OFF: 105 C 221 F 208 psi*
Secondary (RH) or Dual High-speed Fan(s) ON 113 C 235 F 248 psi
Secondary (RH) or Dual High-speed Fan(s) OFF: 110 C 230 F 208 psi

There are other ways to adjust fan switching but going to hypertech was the easiest solution for me.

Another solution is to hard wire a switch on the dash but I didn't want to mess with my dash. I guess I could have velcroed something but that's cheezy. I've been working hard to keep the stock look on this car. But the stereo is fighting me on that one!

jay_blkz28

Thanks for all the feedback. I'm waiting for a day off to work with my fans. Hopefully, ya'lls advice will help me out.