Hrock

I think my car has programming issues with cooling tables or something. My 89 350 runs cool, and never reachs the Fan 1 turn on, yet I park my car after a quick trip and the fan is running.. turn off the computer for a good 15 seconds and restart, no fan. Drive it away and I end up with a fan on even though the temp never reachs 190.

Besides that, My ALDL Plugged in reads the prom so long as I am below 1000 RPM... Above and the stream gets cut off.. Im not sure if that is the tech I reader that is failing..

Any ideas..... Im eating up the current from my alternator and causing un necessary stress on my electrical..


Thanks Guys..
PS. I can not get the VATS to Activate... It shows the flag on, but No Vats failure message when I unplug the leads..

3.8TransAM

Verify your bin vs another stock one and see if you can spot any apparent glitches.

Also it sounds suspiciously like you might have a fan relay or two taking a dump on you.

Might stick on or work intermittently

Also second fan is controlled by the sender in the cyl head, could be flaking out on you as well.

later
Jeremy

Hrock

My Relays have been removed with new ones. Seeing they are not the problem what I have done is just put back the old ones and saving them for later. The HEad Switch I have Bypassed. So the second fan is driven with the primary Via another relay. Both fans come on using the output from one relay that comes from the computer. the computer lead disconnected Via a Gm Weather prrof connector, Fans go off.. The computer is turning on the fans when going for a drive. I Have diagnosed down to the programming. but I dont Know all there is to know about the Duty cycles and stuff..They seem negligant if the fan is on for 100% the car is cold and the duty cycle programmed at 50% or what ever.. But a duty cycle is useless unless you have a time Base. So that is I guess where I am stuck.

John 89 Formula

The green wire with the white stripe is the signal wire from the ecm. If this wire is shorted to ground it will make the fans run.

Where you've done some re-wiring it might be worth checking
out.


Also If your using the arap bin, you have to check the fan flag
or the fan will run constantly

Hrock

Fan Flag being which location, sounds like my problem

John 89 Formula

Look under flags
It's worded differently depending on which definition you are using, but there is only one entry that points to the fan.

Hrock

I have nothing under the flags that refers to Fans.. only Vats and tranny type and tonne of B1 b2 b3 b4 b5 b6 b7

Hrock

OK , Editing field of the ECM $6E , I found that one bit flag stored a notation called " Normally open Fan input" I suppose that was it. I changed it to UNCHECKED, and never noticed a difference.

Im stumped.. The Wires are not shorted. The fan output from the ECM is not Closed or grounded to switch on the Fan relay.
So The ECM has Control, and a quick ALDL (AB) shorting throws the fan on. So that means the output trigger on the ecm works. I mean on a technical level, that if the output driver for the FAN relay was shorted it would keep the fan on at all times. But with Key on and the Engine off I do NOT have a Fan......

So Fan comes on with what ECM conditions ?

FAN on at ( whatever temperature )
Fan on ( AC ON )
DUTY CYCLE
MINIMUM ON TIME ( 15 seconds )
and so on... Am I overlooking something ?

I have gone over the basics.
Shorted wires / Sticking relays / verifying temperature sensors
Checking that this fan is indeed the FAN1 not FAN2 / Checked Hi Limit Sensor for the Fan2.

Grounded fan1 output from ecm to turn on the fan.

Im lost now, Its got to be programming. And I can not find my original PROM code.. I had it, not I dont.. I have been looking for the exact factory code ANYR9338 but no luck anywhere.