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89 relay problem

ken mohr

Well-known member
Joined
Nov 29, 2007
Messages
166
Location
usa
New guy can use a little help. I have an 89 coupe that the main fan (the one in front of radiator) doesn’t run. The high volume aux fans turns on and off properly (on 228 & off 210). I have jumped the main fan and it will operate. Question, Is the relay the one on the radiator shroud drivers side under the radiator hose? Does it run both fans? One parts store shows it runs the aux fan and the other shows it runs the main fan.

Thank you
Ken
 
The Aux fan is set to run a 237F check the sensor at the RH cylinder head.
 
The Aux fan is set to run a 237F check the sensor at the RH cylinder head.


The aux fan is runnig OK. The main fan will not run. I'm not sure of the temp the main fan should turn on but I let the car idle until the aux fan turned on at 227F. Never got any response from the small fan.
 
Turn on the AC the main fan should start up quickly providing your not in a cold climate or below about 45F.
 
New guy can use a little help. I have an 89 coupe that the main fan (the one in front of radiator) doesn’t run. The high volume aux fans turns on and off properly (on 228 & off 210). I have jumped the main fan and it will operate. Question, Is the relay the one on the radiator shroud drivers side under the radiator hose? Does it run both fans? One parts store shows it runs the aux fan and the other shows it runs the main fan.

Thank you
Ken

The Aux fan is set to run a 237F check the sensor at the RH cylinder head.

Most C4 models use two cooling fans,a primary and a secondary.During normal operation the ECM will command the primary cooling fan on when engine coolant temperature reaches 226 deg F,when the air conditioning is on or if a cooling system or coolant sensor diagnostic code is occurring.

The ECM will command the secondary fan to run when the primary fan is running and the air conditioning is on if the vehicle speed is below 55 mph,if the engine temperature exceeds 235 deg F,or if a cooling system or sensor diagnostic code is occurring.

The primary fan is behind the radiator, the secondary is in front of the radiator!!

Welcome to :CAC:Steer:lou:bu:bu:bu :upthumbs
 
We are below 45. I don;t beleive the temp fan between the front of the raditor and bumper has worked since I purchased the vette. The fan visable from the engine compartment does turn on when the air is on. If I am correct the main fan should turn on before the aux fan.
 
Most models use two cooling fans,a primary and a secondary.During normal operation the ECM will command the primary cooling fan on when engine coolant temperature reaches 226 deg F,when the air conditioning is on or if a cooling system or coolant sensor diagnostic code is occurring.

The ECM will command the secondary fan to run when the primary fan is running and the air conditioning is on if the vehicle speed is below 55 mph,if the engine temperature exceeds 235 deg F or if a cooling system or sensor diagnostic code is occurring.

The primary fan is behind the radiator, the secondary is in front of the radiator!!

Welcome to :CAC:Steer:lou:bu:bu:bu :upthumbs

The secondary fan is the one not working. I jumped the fan and it is OK and does run. Now need to check the relay and or thermal switch but don't know their locations.
 
The secondary fan is set to go on at 237F and is the front fan. The sensor is at the RH cylinder head & grounding the lead will run the fan.

We are below 45. I don;t beleive the temp fan between the front of the raditor and bumper has worked since I purchased the vette. The fan visable from the engine compartment does turn on when the air is on. If I am correct the main fan should turn on before the aux fan.
 
The secondary fan is the one not working. I jumped the fan and it is OK and does run. Now need to check the relay and or thermal switch but don't know their locations.
The temp sensor is in the head between # 6 and #8 spark plug!!(2 rear cylinders Rt Head!) :upthumbs

attachment.php
 
Ok too late tonite. I will look tomorrow and let you know. These look diff than the one I thought was it.
 
Junk. thanks for that pic. I am having problems siting the newer hood prop on my oldie!
 
Junk. thanks for that pic. I am having problems siting the newer hood prop on my oldie!
If you need more photos,I've got a 94 here I can take some good ones of what you need!!:upthumbs
 
The temp sensor is in the head between # 6 and #8 spark plug!!(2 rear cylinders Rt Head!) :upthumbs

Found 2 relays. One where you said and one on the wheel well.
temp sensors one on right where you said and one drivers side head between 1 & 3, Not sure which one is the one that may need replaced. Have to check both.;shrug Tried to attach pics. Don't know if I did it right
 
Check out the thread I had going on this exact issue, called "Cooling Mystery", in this forum. Both of the fans died one day on my '88, and I eventually figured it out but it took physically tracing the wires through the harnesses to figure out which relay, switch and sensor does what. Anyway, the pictures and descriptions are all there.
 
This did help. My fan that operates at 228 works fine. The other one which is in front of the radiator on my 89 does not. I will check the relay on my fender well. I need a fan operation around 195 to 200 degrees.

Thank You and Merry Christmas
 
Thank all who have helped and Merry Christmas to all.

Ken
 
I believe you primary fan is working fine because the GM specs is 228+-2F is correct for the fan to start. The secondary if working starts at 237F. Just ground the wire from the sensor at the RH cylinder head with ign. on and the pan should start up if everything is OK.

This did help. My fan that operates at 228 works fine. The other one which is in front of the radiator on my 89 does not. I will check the relay on my fender well. I need a fan operation around 195 to 200 degrees.

Thank You and Merry Christmas
 
Those relays are damn cheap, I recommend just replacing it and keeping one or two new ones on hand.

Happy Holidays to you as well!!!​
 

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