More fun with Fan issues... Different car...

[LGAFF]

Originally Posted by DRM500RUBYZR-1

Maybe 90/91 are different/ but 92 up work as follows:

Fan 1 comes on at 228
Fan 2 comes on if temp gets to 240

Fan 2 turns off when temp falls to 240
Fan 1 turns off when temp fall below 228.
Both fans come on at any temp if AC is turned on.


Marty

This is a Haibeck Chip fans on at 205... doesnt happen.. and the Tech one cannot turn them on in test mode...

[rkreigh]

I had similar gremlins in my old 87 turbo buick


I got tired of trouble shooting and rigged up a direct thermostat and called it a day I know that's kinda hackey for a zr-1, but it's cheap and works great and the fans and puter don't care.

[LGAFF]

This turned out to be an issue with the Prom still waiting to see what the exact issue is with it, maybe the Prom is just bad. I was able to take a 90 Eprom and put it in the car, then use the Tech 1 to turn the fans on and off, that would not work with the 91 Eprom in the car.... and the ECM works fine in other ZR-1s

[LGAFF]

So the chip tested on another 91 and worked fine:

So here is what I know so far:

-91 ECM in 91 w/91 chip; fans do not turn on when temps hit 205 and fans do not turn on when commanded by a tech one(sometimes the will kick on for 1-2 seconds and right off). Fans do turn on when the tech one runs a diagnostic mode; so if you do an ECM check and pull codes

So we know wiring, relays, and fans are good; as fans turn on for diagnostic mode. Ive also tested fans independently, and swapped in know good relays


-If you put a 90 chip in the 91 car with 91 ECM, and tell the tech one its a 90 the fans can be commanded on and off by the Tech one to turn on

-If you put the 91 ECM in a 90 ZR-1 w/90 chip the fans work when at 205 and can be commanded on by the ECM

These tests repeat consistently and same results time and time again. Ive done these checks as well as reseated the prom 10-1t times each.

Any thoughts, this is very odd... I have one wildcard this could be......

[LGAFF]

So the conclusion is that there is something wrong w/ECM that seems to impact the 91 Chips and not the 90s... very odd. Had some videos of the tech one and the different chip results in same car/ECM but they wont load

[LGAFF]

1991 Chip in 91 /w 91 ECM
https://youtu.be/SNCnaClA9go

1990 Chip in 91 with 91 ECM

https://youtu.be/SNCnaClA9go

[-=Jeff=-]

so apparently that ECM is now a 1990 ONLY?

[XfireZ51]

Lee,

Can take 1990 cal, copy it, and put in different prom or Ostrich. Then see what happens.

[Corvette95]

Does the Tech1 show fans requested (on) and they don't run? Pull the connector to the high a/c pressure switch just to see what happens.

[LGAFF]

Originally Posted by Corvette95

Does the Tech1 show fans requested (on) and they don't run? Pull the connector to the high a/c pressure switch just to see what happens.

Hi, Makes no difference....