installed that I burned tonite. I basically took the 89 ARAP bin, and plugged in the tables and constants from my 88 bin. (from $32B cal files). I also pulled some numbers off my ADS chip that I have. I pulled the cold-start injector connector, and fired it up. It started fine, hasn't been run in a while, but idled real good. Just that the primary fan would not shut off. I let the car run for a few minutes, then shut down and checked for codes. None found, then restarted. Fan wouldn't go off. Since it was about 25deg in my garage, I don't think the engine should need any fans on!!

Anyone seen this condition before? Some flag or bit I need to turn off?

Thanks Mike

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Best ET 14.413 @95.57 without
pulling valve covers or manifolds.
Also with stock 2.77 rear end!!!

 

Most likely the A/C pressure switch logic is reversed. The ARAP is set for a normally-closed A/C pressure switch, meaning when you turn on the A/C and the pressure rises this switch opens...telling the ECM you have the A/C on.

I had this problem when I upgraded my '88 setup to ARAP. Have a friend with GMEPro edit the setting to normally-open, it's not in TunerCat that I can see. If you're feeling technical you can open the bin in a hex editor and look at location $C017...bit 5 will be set to 1 for a normally-closed switch. Change this to 0 and re-calc the checksum with your ECM editor.

The A/C pressure switch is located on the A/C line that runs along the passenger side frame rail, has a 2-conductor plug on it. Seems like you could disconnect this and jumper the plug to verify this is the problem...if so, the ECM will see the switch "close" and deactivate the fan.

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1982 Z-28

See http://www.mycar.net/mafb/registry/detail.cfm?id=276 for details

 

Thanks for the info Kevin. I understand what you are saying, and it makes sense. Tonite I tried shorting out the connector to the high-pressure A/C switch, located on the A/C clutch. I have a shop manual, so I know I got the correct connector. When I started the motor, the primary fan still continued to run. I also turned on the AC, and the fan would not shut down either.

I then took a good look at my shop manual, and noticed that there are 3 switches in series, that lead to the ECM, which would indicate a signal for cooling fan control. One is the control switch in the car, to turn on the AC, another is the pressure cycling switch, and the 3rd is the high pressure switch. From what I understand, the cycling switch is normally open, closes at 41-50psi. The high pressure switch is normally closed, and opens above 430psi. The control switch in the car is controlled by the driver. So now I am thinking I shorted the wrong connector out. What do you think?

I would like to prove out this logic before I go burning a new chip. I took a look at the code for my chip, but could not find address $C017. I don't know anyone who uses the GMEPRO, and I couldn't find the flag in Tunercat as you mentioned. I may try to download GMEPRO, if possible.

Thanks again.