Hi. I have a 1995 Chevy Monte Carlo z34 3.4 LQ1 (Under 73k original miles!). The car runs with the temperature in the dash reading mostly at half but sometimes gets as hot as 3/4 or hotter. When the car heats up past half, only the radiator fan #1 (driver side) turns on and no matter how hot it gets fan #2 (passenger side) never turns on. I already tested the fan relays by switching them between the two fans, and fan #1 continues to work properly while fan #2 stays off. I also checked that the motor works by connecting it directly to the battery. The only time both fans work is when I run the car with the ect (engine coolant temperature) sensor(2 wire), located on the lower intake, disconnected(check engine light turns on when disconnected). So I changed that out, but my fan problem persists. The car also has a "single wire" temperature switch on the engine block that I'm planning to change next. The coolant level sensor on the radiator doesn't work either; the low coolant light is always on, even if it's not low. I doubt the coolant level sensor has anything to do with the fans, plus it "only" costs 50 bucks at Autozone. Any help will be much appreciated.

 

Did you ever sort this out? I'm having a similar problem.

 

You got a tough one. The troubleshooting chart for electric engine cooling fans is 8 pages long, but most problems are with either the PCM or a short in the "Bottom Underhood Electrical Center" mounted on the passenger side fender well. Check for corroded grounds. As for the "Low Coolant Level" always on, I've had the same problem for 3 years. Engine sludge from a past LIM gasket leak coats the probe of the coolant level sensor so the probe can't read, sending a false signal. I've had the radiator professionally flushed and replaced the sensor and still have the problem. I might try flushing with a chemical additive sometime in the future.

 

"Did you ever sort this out? I'm having a similar problem." - anagy007

No, I still have the fan problem. I changed the "coolant temperature sensor" (2-wire, located under throttle body) and the "temperature switch" (single wire, located on the engine block[only responsible for your temperature gauge]). I bought the a radiator coolant-level sensor from ebay for 6 dollars, but I've been too lazy to replace it. It's most likely going to be the fix in my situation. I'll post when I replace it, but I doubt its going to be anytime soon because I don't even use that 10mpg, gas chugger. Do you have a 95 z34 also? I'm curious to know how many miles you get per gallon? As for your fan problem try to disconnect the coolant temperature sensor located under the throttle body(kind of hidden), run the car and see if the fans come on. If they do, I would just run the car with out that sensor. Your Temperature gauge WILL still work properly. You will get a check engine for the disconnected sensor, but you'll eliminate the chances of overheating due to no air flow.

 

I just had my mechanic do a coolant flush and replaced the coolant sensor. He said that apparently the refrigerant pressure needs to be at 175. Does that make sense? However, the coolant sensor light still comes on intermittently. He did a bunch of much needed work, but the AC is still not as cold as I think it should be.

P.S. I have a 99 z34 with 122k miles.

 

Sounds familiar. Not sure how your mechanic is reading the refrigerant pressure. Normally the high and low pressure sides should be 50psi under static pressure. Refrigerant oil can't mix with engine coolant, but both fans are supposed to turn on by grounding the 3rd fan relay when A/C is turned on. If your still having coolant level sensor you have the same annoying problem as me and still have a thin film of sludge coating the probe of the sensor. It will go from intermittent to almost constant. Would love to know the solution if you ever get it solved. Have been dealing with mine for 3 years now.