85 vette main cooling fan not coming on

[85c4yellow]

hi im new here in the forums i have an 85 coupe and i cant figure out with my main fan behind the radiator wont come on either when u turn on the ac or when the temp goes up idling i already replaced the relay for it and jump it with a jumper wire like the book says and the fan kicks on but not with the relay. and also my check engine light is on and i cant get any codes from it its just solid on and i cant get it to flash, is my ecm or prom bad?:confused ;helpany help would be apreciated it thanks.

 

[bucket]

hi im new here in the forums i have an 85 coupe and i cant figure out with my main fan behind the radiator wont come on either when u turn on the ac or when the temp goes up idling i already replaced the relay for it and jump it with a jumper wire like the book says and the fan kicks on but not with the relay. and also my check engine light is on and i cant get any codes from it its just solid on and i cant get it to flash, is my ecm or prom bad?:confused ;helpany help would be apreciated it thanks.

unplug it and jump the fan and see if its good...
howdy

 

[Schrade]

Welcome onto the boards there!

When you jump it, don't hold onto the paper clip too long, because 30 amps goin' through a paper clip starts to glow real quick, and you probably don't want to hold on when it does for very long. This is also a good test for the FTS finger temperature sensor. :W

Never mind the notes there... (this is '94, yours might be similar)

 

[Schrade]

If you jumped the switch, and the fan worked ('A' to 'E', in my diagram), then either there's a blown fuse (line 'D', my diagram), OR, the ECM to relay line is open (line 'F', my diagram), or the open or short is further 'away' from the relay.

Start by checking 'D', and 'F'. 'D' should give you 12V, coming FROM the fuse to the relay. 'F' should ground out the circuit for the relay THROUGH THE ECM, BUT ONLY WHEN THE ECM SAYS THE CONDITION IS RIGHT (LIKE 228 TEMPERATURE)

You can tap line 'F' to ground (IGNITION OFF), then turn the key to 'ON', and the fan should come on. That will only confirm relay function.

Then if it still does not work, the ECM is not getting the temperature signal in the ECM to close the ground circuit through line 'F'.

Do the paper clip trick, and confirm your CoolantTS DTC fault. Do you know the code trick?

 

[vetteoz]

Do the paper clip trick, and confirm your CoolantTS DTC fault. Do you know the code trick?

He says"
also my check engine light is on and i cant get any codes from it its just solid on and i cant get it to flash, is my ecm or prom bad"
ECM may be on the way out , or gone!

 

[Schrade]

He says"
also my check engine light is on and i cant get any codes from it its just solid on and i cant get it to flash, is my ecm or prom bad"
ECM may be on the way out , or gone!

kaNt reed 2 well man - whent too pUblik skool

spelchek makes mi cpu smoke to! Im a whiz reedin' piktures tho.

 

[85c4yellow]

i took the ecm off and got it look at this local corvette shop and they told me it was fried so i got a replacement for $140 so now the car runs no prob fan comes on ac is great, the prob now is that i get a code 52 wich is my oil temp switch so i got a new one threw it in connected the batt and i get the same code again so i have to check the wiring to the switch but thanks for the help guys.

 

[vetteoz]

the prob now is that i get a code 52 wich is my oil temp switch so i got a new one threw it in connected the batt and i get the same code again

Shouldn't have a DTC 52 on your car

Code #52 (1990-91 Corvette Only): Engine Oil Temperature Sensor Low.

 

[Schrade]

i took the ecm off and got it look at this local corvette shop and they told me it was fried so i got a replacement for $140 so now the car runs no prob fan comes on ac is great, the prob now is that i get a code 52 wich is my oil temp switch so i got a new one threw it in connected the batt and i get the same code again so i have to check the wiring to the switch but thanks for the help guys.

Told? Or SHOWED??? GO BACK RIGHT AWAY, AND GET IT BACK, UNLESS THEY CAN SHOW YOU THAT IT NEEDS BUTTER (like a DTC 51, for starters (depending on year))...

 

[85c4yellow]

well i droped it off and thats what they told me that i needed a new one so i get the new ecm and they took the prom off my old me and i plug it into the new one and if im not supposed to get a code 52? because of my car being too old then why do i get that code? the light will flash 5 times then 2 three consecutive times then it will start all over again

 

[vetteboy86]

I think you are getting a code 12. The SES light flashes 12 three times I think than flashes the codes, than 12 three times again at the end of the codes. It's been a while but I think this is correct.

So what should happen.

1 flash pause 2 flashes longer pause 1 flash pause 2 flashes longer pause 1 flash pause 2 flashes longer pause (this is the section the codes will flash in the same order the 12's did) than flash 12's again like at the beginning.

 

[85c4yellow]

yeah and after that then it will flash 5 times then 2 times in that same sequence three times then it will do the 12 again

 

[vetteboy86]

Well that does sound like a 52. I'll have to dig a little bit more.

 

[Schrade]

If 52 is an ECM code, it does NOT mean the ECM is necessarily bad. It MIGHT mean that the fuse for power TO the ECM is bad, or a wire with power INTO the ECM is shorted (less likely, since you have comm's), OR, the primary ground for the ECM is bad...

DTC's are for a CIRCUIT, not necessarily for the device ON the circuit.


From here... (notice faulty ECM is LAST yup...)
CODE 52
Trouble Code 52 indicates that the ECM sensed a fault with the CALPACK. The CALPACK is a plug-in module separate from the PROM, that contains preset calibrations used by the system during "limp home" (backup) mode. The ECM continuously checks for its presence while power is applied.
The conditions for setting this code are:

• the ECM does not sense the CALPACK

Typical causes for this code include:
1) Incorrectly installed CALPACK module
2) Incorrect CALPACK module for this vehicle
3) Defective or incorrectly inserted PROM
4) Defective ECM

 

[85c4yellow]

well i got a new chip from hypertech with a new thersmostat and the car runs way better performance wise but i keep getting the same code 52 and i hooked up my scanner and the scanner reads no codes but if i do the jumper thing then it gives me code 52 where is the ground to the computer located at?

 

[WhalePirot]

You should get a FSM for your car. Then you can locate ALL the grounds and check them for a good connection, while quite probably saving yourself the cost of the manual in parts/services that do not fix the problem. I added extra ground straps as these ECM cars need good electricity flow, meaning good connections, from big grounds to the small weather pack plugs for the 'exposed' circuits.