nlzn

I've been dealing with this issue for a while. The fans will not come on to the point of the coolant boiling.
Now, a fan will spin up with the A/C on. Both will spin up when it pops the SES lights (AIR pump failure is tripping the SES.) I have replaced the coolant temp sensor with a brand new OEM one. I consider the gauge cluster temp sensor to be close to accurate as its boiling at full hot. I've also replaced the relay for the fans.

Any suggestions for a ninja fan problem? (I mean its annoying but the SES light will come on when its in neutral so I can keep them running at stop lights.. I can manage it but a true fix would be nice.)

lt170chevelle

iTrader: (2)

did you change the right coolant sensor? the one in the head is just for the temp guage. The one that is in the front of the water pump is the one that controls your low fans. also if worst comes to worse, you can wire up your low fans to run all the time.

95TransAm_ToM

thats right you can go to this website and pick a harness up http://www.lmperformance.com/763/2.html

Zralou

iTrader: (3)

I have the same problem, fans won't turn on even when the overflow is boiling over. I also replaced the temp sensor (the one in the water pump) but no difference.
The fans work ok, jumping the ALDL kicks them on, and i've now wired a switch on them (shbox.com).

What I found was the problem, was when I hooked up a scanner. At the point where the car was boiling over, the PCM seeing a temp of 180*, so although the fans are fully functional, the PCM isn't turning them on because it doesn't know the right temp.
What I don't know is why this is happening, as I said, i've replaced the sensor, and i've checked the wiring voltage and resistance, my guess is the PCM or the new sensor is the problem.

Sara Lou

LT1

iTrader: (1)

i wonder if your cooling system has air pockets, causing your tempture to read low and fan not turning on. Whats your guage reading when its hot?

Zralou

iTrader: (3)

On mine, the gauge seems fairly accurate, when its boiling, its in the red.

I've bled the system a couple of times, other than sitting in traffic, the car runs cool (160* stat) at normal cruising, and if I flick the fan switch, it will stand idling all day no problem. Also, if I let the temp creep up, I can flick the switch over to high speed fans and it will bring it right back down.
Sorry for hijacking, just hoping we can both get some info from this.
::Edit:: forgot to add, i've also reprogrammed the PCM to turn the fans on sooner (195*) but still no difference.
Sara Lou

nlzn

Yes, the coolant temp sensor should be one the PCM takes the read off of, while the cluster reads off of the one in the intake manifold. The harness looks good for the CTS.. does anyone know the values it should read if I back probe it with a multimeter?
Second, I know the dash guage is accurate. When it hits full red hot coolant is indeed boiling.
I will wire a switch up for this if I cant figure out the problem, its just majorly annoying.

lt170chevelle

iTrader: (2)

yeah in both cases you should change the coolant sensors if you do not get a change on the voltmeter. its going to either produce a ground to turn the relay for the fan on or it will send 12 volts to the relay.just test the wires cold.write them down, then test the wires when the motor is 210+ and compare..if no changes are made then you know you have a bad sensor.Always test the sensors before replacing them otherwise it can sometimes be a waste of cash.Also if this turns out to not be the problem, you can ohm out the wire from the sensor to the relay to see if there is a short. sounds more complicated than it is. just be willing to spen about two hours to check everthing

Zralou

iTrader: (3)

You can find the values here:
http://shbox.com/1/4th_gen_tech2.html#ect

Sara Lou

Formula350

iTrader: (3)

Driver side head, not intake. Only TPI had a temperature sensor in the intake, and that wasn't for coolant.