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The relay is the stock relay. Do you have a suggestion for a replacement that has the diode you are talking about? I am being serious.
Frankly I do not know how to do continuity using a multimeter. Off to YouTube.
Is there any chance that I should be switching the A to the battery and E to the fan.
Thank you.
https://www.gmpartsgiant.com/parts/g...-10038311.html
For continuity check find the Ω symbol on the meter, then touch the probes to each pin till you get a reading, relays are typically 800 ohms.
Switching A and D will have no effect on operation.
1985 is different. The drivers side head temp switch works the temperature gauge in the dash and the passenger side head temp switch works the front of radiator pusher fan if you have one. The temp switch in front of engine in the intake works the puller fan behind radiator and that switch sends signal to ecm. The 1986 and up switches on the heads are switched. pull your drivers side switch from head and your temp gauge will not work just to prove.
1985 is different. The drivers side head temp switch works the temperature gauge in the dash and the passenger side head temp switch works the front of radiator pusher fan if you have one. The temp switch in front of engine in the intake works the puller fan behind radiator and that switch sends signal to ecm. The 1986 and up switches on the heads are switched. pull your drivers side switch from head and your temp gauge will not work just to prove.
You are absolutely correct,FSM says temp switch by dipstick will trigger main fan, should have fact checked myself lol.
So... to bring it all together:
Front temp sender-->ECM coolant temp sensor
pass side by dipstick --> overheating switch
driver side under between 1 and 3 ex runner-->dash signal
Disconnecting the temp sender will cause the main fan to run at full speed, this verifies the ECM can control the fan, grounding out the passenger side temp switch verifies the overheating circuit works.
Disconnecting the front sender will cause running problems though, but the fans will run in the key on engine off position IIRC.
It's funny you say this. I have an 89 and this weekend. I opened the hood and a fan was running but the one behind the radiator was not moving. I went home and grounded the GRN/WHT wire in the driver's side head and the puller fan did not come on but the small fan in the front of the radiator did. I also found a GRN/WHT wire that seems to go to C100 but it is not connected to anything. I ground it and no fans ran. I need to look at the 89 FSM to see WTF.
So then there is another wire that goes from a switch in the front of the engine. And that wire needs to be connected to the relay. Correct?
I went to look at the 85 Corvette I took a picture of the front of the motor. For two reasons. One to verify that the connector with the yellow wire is the one that is the temperature sensor that activates the fan. Two the nipple with no hose on it where does it go to. I cannot find it on the AC schematic or the cooling fan drawings.
I went to look at the 85 Corvette I took a picture of the front of the motor. For two reasons. One to verify that the connector with the yellow wire is the one that is the temperature sensor that activates the fan. Two the nipple with no hose on it where does it go to. I cannot find it on the AC schematic or the cooling fan drawings.
Is your 85 dual fan or single fan?
Single fan models have the overheat switch and the ECM controlling the main fan, dual fans only the ECM can control the main fan, the temp switch is reserved for aux fan control.
The hose fitting is for the throttle body heating circuit, most people bypass it.
Last edited by ThatOneKid; Jun 15, 2021 at 12:58 AM.
Hello, I got off my lazy *** and took apart the radiator shroud. The 85 is a dual fan. I ordered and received the relay. But it is four pin and only takes a four pin connector. I will have to order one. I am reading something you sent me
Front temp sensor - ECM coolant sensor-- this is in the intake manifold?
pass side dip stick-- overheating switch
Drivers side ------ dash signal
From the picture above there are two sensors in the intake under the thermostat housing. I think the fan one is the switch/sensor with the black and yellow wire.
I have the two fan wiring diagram in front of me"Y-CAR-124". It dos not have that wire on the diagram/schematic.
I really appreciate your help
Hello, I got off my lazy *** and took apart the radiator shroud. The 85 is a dual fan. I ordered and received the relay. But it is four pin and only takes a four pin connector. I will have to order one. I am reading something you sent me
Front temp sensor - ECM coolant sensor-- this is in the intake manifold?
pass side dip stick-- overheating switch
Drivers side ------ dash signal
From the picture above there are two sensors in the intake under the thermostat housing. I think the fan one is the switch/sensor with the black and yellow wire.
I have the two fan wiring diagram in front of me"Y-CAR-124". It dos not have that wire on the diagram/schematic.
I really appreciate your help
Yep, the temps sensor is located in the coolant passthrough made into the intake base immediately before the thermostat.
Yellow wire is the ECM input, red is the thermo-time switch for the cold start injector, it is not part of the cooling system.
Last edited by ThatOneKid; Jun 19, 2021 at 09:22 AM.
So this morning. I ground the switch, passengers side head. The relay clicks. But the fan does not turn. I put a probe on the fan wires no power.
I removed the ground from the switch. Both the GRN/Whit and Blue wires have power.
I disconnected the GRN/Wht wire from the relay and turned on the key. It has power. Should it?
If I run a wire from A to D the fan runs. Oh and I had an old relay lying around. Same thing clicking but the fan is not running.
I went to my FSM and I cannot find any of the information that you shared with me. I mean the ECM and temp sensor. Where is it. I am in the COOLING SYSTEM (dual fan) TROUBLESHOOTING HINTS nothing
"Front temp sensor - ECM coolant sensor-- this is in the intake manifold? pass side dip stick-- overheating switch Drivers side ------ dash signal"
Where should I be looking so I can see this information.
I went to my FSM and I cannot find any of the information that you shared with me. I mean the ECM and temp sensor. Where is it. I am in the COOLING SYSTEM (dual fan) TROUBLESHOOTING HINTS nothing
"Front temp sensor - ECM coolant sensor-- this is in the intake manifold? pass side dip stick-- overheating switch Drivers side ------ dash signal"
Where should I be looking so I can see this information.
Thank you
Cold start injector is part of thr starting system on page 116, coolant temp sensor is ECM inputs on page 129. Looking at the diagrams something ain't right with your car, you should have a purple and tan wire for the thermoswitch.
So this morning. I ground the switch, passengers side head. The relay clicks. But the fan does not turn. I put a probe on the fan wires no power.
I removed the ground from the switch. Both the GRN/Whit and Blue wires have power.
I disconnected the GRN/Wht wire from the relay and turned on the key. It has power. Should it?
If I run a wire from A to D the fan runs. Oh and I had an old relay lying around. Same thing clicking but the fan is not running.
Thank you all
The switch in the head won't run the main fan but it should run the aux fan, the small fan in front of the radiator.
If you disconnected the coolant temp sensor and the main fan did not run that means the issue is between the main fan relay and the ECM.
Here's a pic with the different locations of the two relays:
Can you confirm which relay you are working on?
So to take a step back:
The main fan has its own relay and is controlled solely by the ECM, it has no redundant switch to get it to turn on.
The aux fan is solely temperature switch switch controlled and has no connection to the ECM.
To test the main fan, disconnect the coolant temp sensor with the yellow wire, which is located at the front of the motor in the intake base.
To test the aux fan, ground the green and white wire on thr passenger side head.
Hope this helps, you're making progress but I think it's time to pull the passenger side hush panel and jump the pin D2 TO D3, if that gets the fan to work but unplugging the coolant temp sensor does not, the ECMs internal circuitry for the fan is toast.
Last edited by ThatOneKid; Jun 19, 2021 at 02:47 PM.
Yes, you are correct. This is a replaced TS. As I went further along the wires are tan and dark purple. I found the auxiliary fan relay. I tested the red wire. It dos not have power. The wire goes into C100. I turned on the key still no power. Because it is a fusible link. I am going to run a fused wire from the battery. The blue wire has power with the key on. The other wire in the relay does not have power with the key on.
I am thinking that the problem I am having with the main relay is that with the key on both the blue and GRN/White wires have power. So when the relay kicks in the voltage goes crazy.
Any ideas?
Thank you
The switch in the head won't run the main fan but it should run the aux fan, the small fan in front of the radiator.
If you disconnected the coolant temp sensor and the main fan did not run that means the issue is between the main fan relay and the ECM.
Here's a pic with the different locations of the two relays:
Can you confirm which relay you are working on?
So to take a step back:
The main fan has its own relay and is controlled solely by the ECM, it has no redundant switch to get it to turn on.
The aux fan is solely temperature switch switch controlled and has no connection to the ECM.
To test the main fan, disconnect the coolant temp sensor with the yellow wire, which is located at the front of the motor in the intake base.
To test the aux fan, ground the green and white wire on thr passenger side head.
Hope this helps, you're making progress but I think it's time to pull the passenger side hush panel and jump the pin D2 TO D3, if that gets the fan to work but unplugging the coolant temp sensor does not, the ECMs internal circuitry for the fan is toast.
I found in a lot of cases you cannot go by the fsm concerning the 1985 model year as they refer to 86 and up in a lot of cases. I am guessing you found the aux fan relay piggybacked behind the main fan relay? And so on it could go.
OKAY, THANK YOU ALL.
IT IS ALIVE!!!
So I wired the fan relay exactly the same as the fan auxiliary fan relay and it WORKS, YiPPIE!!!!
Al kidding aside. You guys are great. Without you this would have ended up at some shop and costing me god knows what. Thank you all
Happy Father's Day
Here is the secret formula
5 pin relay and five pin connector
E power
D- empty has no blade in the relay
C-Blue -fuse panel
B- GRN/White wire
A- Fan
Before this the GRN/White had power with the key on. Now when I probe the GRN/White, key on, the fan spins. I have not run the car. The block on the heater hose bypass broke. So I lost a lot of coolant. I am going to try and clean up the heater core piping. Maybe replace the heater core. Then run it. But, I am sure it will work correctly. Grounding the switches turns the fans.
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