I have a 95 z28. The cars cooling fans are not coming on when the car gets hot. Hot=right before red line.

After doing my research this is where I am at.
1. Replaced the coolant, lines, and completely flushed system at dealership.
2. Checked fan motors by hooking to battery (good)
3. Connected the DLC pins 5 and 6, keyed on car and fans came on
4. Replaced temp sensor
5. Fuses and Relays are new
6. I have reset the PCM with no results.

I am not the best with electrical issues like this and I am not sure where to look next. I am about to take the car to a dealer but I really don't want to if I can avoid it.

Any advice would help.

 

on the temp sensor you replaced the one in waterpump or the one in head? Couple things off the top of my head I tried recently was turn ac on given its charged up and see if they come on. You can also try to disconect the maf sensor and start car and they should come on (and probably set a code). Might want to scan it and see that the scan temp is reading similar to the dash guage(they use different sensors) Shoebox website has info on testing the temp sensors and has the wiring schematics.


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The sensor that I changed was the one by water pump. If I read correctly having low ac charge will only cause the ac fan not to come on but the main fain will still work. I saw the electrical lay out and when u test the line were would you test the connector ends?

Also if the fans weren't getting enough power how would they come on by connecting those 2 pins on the DLC?

 

Sounds like air in the cooling system. Have you bled the cooling system? Both at the bleeder on the thermostat neck and the bleeder on the heater line (with the heater on full and max temp)?

 

Are you sure the dash gauge is accurate? If it's approaching the red zone, and the PCM is not commanding the fans on, it may not be accurate. As you probably noted in Shoebox's article, the fans should go to low speed at 226*F and high speed at 235*F. If you interpolate linearly, the red zone on the gauge starts just past the 3/4 line, which would be 235*F. A small error on the gauge might explain the fans not coming on.

It would be helpful if you had access to a real time scanner, or scanning software, that would tell you what temperature the sensor in the water pump housing is indicating to the PCM.

 

There is no a/c fan as opposed to main fan. There are just fans.

Fans will always operate by temperature thresholds no matter what (if working properly). They won't come on with the a/c if a/c operation is inhibited from a low charge (and subsequent trouble code because of such).

 

I have a scanner that says it reads obd1 button when I connect it says it won't connect and that's using the ob2 connector(its obd 1 and 2 capable). I saw how to make the connection to rig up the obd1 to the pins which im going to do tomorrow. I know it's getting hot because steam is coming out of engine bay and it caused the old cooling line to leak (which I replaced them)

Shoebox when I connected the 2 pins which caused the fans to come on did that cause a surge in power to kick the fans on? Because im just tying to figure out why that would let the fans turn on but why nothing else will.

Also when the coolant was changed they used a device that used pressurized air to fill the coolant and i do not believe they used the air bleeding points as mentioned. Also judging by what came out of the radiator the coolant had not been changed since new.

One other thing I read that the car running rich and coolant fans not coming on may be connected, is this true?

Thanks everyone for the help and advice.

 

I dont know as much as the two other guys but will share what I (think) I know. The reason it kicked the fans on when you jumped the pins isnt a power surge it just shows the computer can command the fans on(I think it does so by a ground). Since it can command the fans on probably means the wiring and relays are working as they should. This to me would cause me to focus on the signal to the pcm(thats why a couple of us suggested scanning and looking at the temp compared to dash guage and turn on temps). If the temp sensor(in waterpump) is not giving accurate temps to the pcm then that may be your problem or the sensor wiring. That can also effect the fueling(if pcm is not getting an accurate temp reading). If you cant gwt your scanner to connect getting an aldl cable and using the free software may very well be worth the cost of the cable. Good luck.


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If you read the link that RamAir95TA posted, it tells you that jumping the DLC turns the fans on. That's normal. There is no connection to running rich and fans not coming on. You need to see what the PCM is seeing as far as temperature.
If you had a leaking hose, it was going to leak no matter if it was overheating or not. So, that is not a positive indication of overheating.

 

What scanner do you have? If it's an Innova, it may not work.

Where is the steam coming out under the hood? The reservoir is the only "open" component in the cooling system.

 

That is the scanner I have but i have the od1 connectors. There is a picture showing what two prongs to attach to the port. Will that work? If not what is a decent inexpensive obd1 scanner. Called the dealer and got a quote of 110 to scan the car. .. really to plug something in that much. Lol I knew there was a reason why I stayed with carb engines for so long.

 

Whatever you use it has to be something more than only reads trouble codes. It has to be capable of showing live engine operating parameters.

Look at the sticky at the top of the forum. It gives info on free software that can be used with a $60 or so cable, plus a PC or laptop.

 

So i went to the dealership and i got nothing from them expect for: Im not sure... I think... It'll take 4 hours... so at that point I said forget it and went back home. By this point I get back to the house put the car back on the rack and i see just a little steam coming from the radiator. I looked at the temp gauge and it was at 1 hash line before the red for my coolant. At that point I was about to turn on the heater to get rid of some of the heat and I hear a fan kick on. I look under the car and its the passenger side fan that came on to cool the coolant. Is this the correct fan that should be coming on? And why now is the fan working? The only thing different was that I drove the car this time to get it to operating temp instead of letting it idol to temp.

 

BOTH fans should run at the same time on your 95. Perhaps you should test the fan that did not come on. If you can't get something to let you look at operating parameters of the PCM (like the engine temp), you are just going to keep chasing your tail and wondering if the fans are being commanded on at the right time.

If you are seeing steam, you have a leak somewhere. If you have a leak, you can also get air in the system. If you get air in the system, it can cause erratic temperature readings from the sensors. If you have erratic temp readings, the PCM may not command the fans on when you expect.