Well, I went after my codes this afternoon, in an attempt to find out why my fans are not functioning.

I locate the diagnostic terminal, connect my jumpers, and turn the key to run. Nothing. Zip. No "Service engine" light. So, off goes the key, pulled the jumpers, and went after the "Telltale" area of the dash.

Found some interesting things. One, these cars were going to have a low tire pressure warning light huh? And I had no IDEA I had a light that indicated a hatch ajar. Seems that printed circuit board on the back,that the bulb housings screw onto was not making contact very well with several indicator bulbs. Fixed THAT problem.

After I got the dash reassembled, I ran my diagnostic test, and VOILA! My "Service engine" light was flashing a code "12" and ONLY a code "12"! Happy day.

Now, I am at my wits end trying to repair this fan. I jumpered diagnostic terminal "B" to ground "A" on my ALCL. Fan started. Checked all voltages, and all seems well. Even replaced the cooling fan relay. (Next to the master cyl) Nothing. STILL doesnt run. Turned on the A/C, Nothing. As I understand it, if the A/C is on, the main fan will run. Correct?

The pusher fan is missing on this car. The previous owner, for whatever reason, took it off. The wiring is disconnected to where this fan was mounted. Would this cause the main fan not to run also?

I am getting tired of poking that damn probe into my finger all afternoon. Anyone have any ideas??

Grounding issue? Power? BTW '87 coupe



[Modified by Thomas, 7:36 PM 5/29/2002]

 

OK, you have found out a lot!

The fan works, but not with the AC on. AC must have sufficeint charge to turn the main fan on. Does the AC run nice and cold?

Main coolant fan will not come on until between about 220 and 230*F. If you coolant temp gets near there and still no fan, you need to check on the ecm coolant temp sensor that is located below the TB.

 

I probably won't be of much help to you but.......I understand the fan will run when the engine is running with the a/c ON, when, the a/c compressor head hits 190 PSI. The fan won't turn on if the engine's not running etc. Didn't know if you had your car running when you were checking everything. :confused:
Good luck.

 

Nope. The A/C NEEDS a charge ,,,,,,,,,,,,,,,,,,,,

 

Found it. If that was faulty, wouldnt it kick out a code? And that thing looks like a MOTHER to get at,,,,,,,,,,,,,,,,,

[Modified by Thomas, 8:22 PM 5/29/2002]


[Modified by Thomas, 8:34 PM 5/29/2002]


[Modified by Thomas, 8:35 PM 5/29/2002]

 

If the sensor is very bad it will set a code 14 (crazy high temp) or 15 (crazy low temp). If slightly bad it may not.

What you have tested so far indicates that the fan works and that the ecm can drive the fan. What we do not know is if the ecm is commanding fan at the correct temperature.

Fan should come on somewhere around 220 to 230*F. Note, the dash temp guage uses a seperate temp sensor. Does the fan engage between 220 and 230*F? If so this is normal, if not we need to trouble shoot further.

BTW, aux fan (pusher) was an option available with I believe the Z51 package, check regular production option (RPO) codes on lid to center console. It was controlled solely by an aux fan coolant temp switch (sensor) mounted between #1 and #3 cylinders in the head. The switch grounded a relay located on the fan shroud which powered the aux fan. No ecm control of the aux fan at all, just temperature. This was set about 10* higher than the main fan.

ECM coolant temp sensor (below the throttle body) can be tested with an Ohm meter. AT 70*F it shoud read about 3,400 ohms. At 100*F it should read around 1,800 ohms. At 40*F , it should read around 7,500 ohms. This is across the sensor terminals with the wires disconnected.

Good Luck

Pete

 

Yup. The fan on my car is missing, but HAD it. Relay is there, as is sensor in the cyl. head.

Again, no codes are being reported. Main fan NEVER runs. I let it idle up to 240 degrees in the drive after the flush and fill. Fan never started.
This is my next test then,,,,,,,,,,,,,,,,,,,,,,

 

never mind i read the wrong section of manual



[Modified by mikes84vette, 9:36 PM 5/29/2002]

 

Well, I tried to check the coolant temp sensor in the car. Not to easy to get on the terminals, so I removed it. As far as I can tell, it's ok. Ran it under hot water, then dipped it in a bottle of water I had in the fridge. I KNOW what that water temp is, and the Chiltons manual tells me what the Ohm values were supposed to be. I am quite sure the sensor is ok. I am replacing it anyway, its out.

Now, I have to determine if the feed wire to the sensor has continuity. If it DOES, I am at a loss. I will check the ground also

More ideas would be appreciated. I will keep you posted.....

Thomas.

 

Fixed. Temp. sensor. Pete, Mike, Thanks

Tom

 

:cheers: