Manual fan switch
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
On earlier models, the fan is switched on by the ECM grounding the wire from the relay.(battery to relay to ground)
Usual way of manual operation is to splice into this wire and ground it through a switch so still have ECM control over fan with manual overide when required.
Usual way of manual operation is to splice into this wire and ground it through a switch so still have ECM control over fan with manual overide when required.
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
dont know what your problem is but i bought an aftermarket fan relay and temp sensor made by painless from jegs. it turns the fan on at 175 off at 160 around there for right at 50 bucks. no manual toggle needed.
Pro
Joined: Oct 2005
Posts: 557
Likes: 1
From: Ottawa Ontario
Manual control of your cooling fans.
I have a 92 LT-1 convertible with the 6-speed transmission. I, also, have a Meziere HD electric water pump installed. This Tech Tip will explain how I installed switches that allow me to turn on the primary and secondary cooling fans. When the switches are turned off, the ECM regains normal control over the cooling fans. Placement of the switches is up to the owner, but I will explain where I installed mine. List of materials (things you need to get): 14-16-gauge wire, I chose colors to match the wires I spliced into. (green and blue for my car) Two rocker switches, just on-off type (don’t get the lighted rocker switches). Hardware to mount the switches Some tie wraps Electrical tape Soldering gun and solder First a lesson on how the fans work on a 92 Corvette. The 92 uses a primary and secondary fan system, as compared with the two-fan system that uses low and high speeds used in later models. The ECM controls the fans by grounding the signal circuit of the relays. The ECM first turns on the primary fan when it reads a preset oil or coolant temperature. At a higher temperature, the ECM will turn on the secondary fan for additional cooling. There is also an input to the ECM from the VSS (vehicle speed sensor) that turns the fans off at certain speeds. When the A/C is turned on, the fans are also turned on. What we’re going to do is intercept the ground side of the signal circuit of the relays and put a switch inline to ground. Once grounded, the signal circuit is complete and the relay closes and the fans come on. Simple. Now, let’s find the two relays that control the fans. They are located on the driver’s side of the engine compartment mounted on the side of the radiator housing. Notice that each relay has four wires running to them. Two wires are heavier gauge and two are lighter gauge wires. Of the two lighter gauge wires, one is “key-on” power and the other goes to the ECM for grounding. You can identify the “key-on” power by its color. Both relays will have this same color wire going to the relay. Once you find this same color wire running to both the relays, the OTHER lighter gauge wires are the ones going to the ECM and they are the ones we want to work with. On my 92, the primary fan relay ground side of the signal circuit is green and the secondary one is blue with a white stripe. I unwrapped these two from the harness wrap so I could work with them. There is a very convenient ground just aft and below the fan relays. If you choose to put your switches in the engine compartment, this is a good place to mount the switches. I placed my two switches in the center console inside the cockpit. I never used the cup holder so I removed the rubber lining and fabricated a switch panel that fit right over the cup holder. That way I could cover the switches with the lid that slides in and out. I used the ground wire that is part of the accessory plug in the console to connect to one side of the switches. Then, using colored wires for identification, I ran the two wires from the switches to the engine compartment. Yes, I removed the lower trim panel, to gain access to the grommet that holds the hood release cables which is where I ran the wires through the fire wall. (Hardest part of the project) Now, just make the connections, primary ground side signal wire splice wire to switch. Then, secondary signal wire to the other switch. I soldered these connections and taped very well and stuffed them back into the harness wrap. Reconnect the battery and turn the key on. Turn the newly installed primary cooling fan switch on and you should hear or see the primary fan come on. Try the secondary switch also. You’re done! A few notes about the use of this modification, These fans are high draw items and will run your battery down if you turn them on and forget them. At the track, I’d use your tow vehicle and a set of jumper cables so you won’t let “Murphy's Law” get you. For normal driving, turn them off once you are going into cruise mode. This mod along with the electric water pump allows you to keep the C-4 a lot cooler.
I have a 92 LT-1 convertible with the 6-speed transmission. I, also, have a Meziere HD electric water pump installed. This Tech Tip will explain how I installed switches that allow me to turn on the primary and secondary cooling fans. When the switches are turned off, the ECM regains normal control over the cooling fans. Placement of the switches is up to the owner, but I will explain where I installed mine. List of materials (things you need to get): 14-16-gauge wire, I chose colors to match the wires I spliced into. (green and blue for my car) Two rocker switches, just on-off type (don’t get the lighted rocker switches). Hardware to mount the switches Some tie wraps Electrical tape Soldering gun and solder First a lesson on how the fans work on a 92 Corvette. The 92 uses a primary and secondary fan system, as compared with the two-fan system that uses low and high speeds used in later models. The ECM controls the fans by grounding the signal circuit of the relays. The ECM first turns on the primary fan when it reads a preset oil or coolant temperature. At a higher temperature, the ECM will turn on the secondary fan for additional cooling. There is also an input to the ECM from the VSS (vehicle speed sensor) that turns the fans off at certain speeds. When the A/C is turned on, the fans are also turned on. What we’re going to do is intercept the ground side of the signal circuit of the relays and put a switch inline to ground. Once grounded, the signal circuit is complete and the relay closes and the fans come on. Simple. Now, let’s find the two relays that control the fans. They are located on the driver’s side of the engine compartment mounted on the side of the radiator housing. Notice that each relay has four wires running to them. Two wires are heavier gauge and two are lighter gauge wires. Of the two lighter gauge wires, one is “key-on” power and the other goes to the ECM for grounding. You can identify the “key-on” power by its color. Both relays will have this same color wire going to the relay. Once you find this same color wire running to both the relays, the OTHER lighter gauge wires are the ones going to the ECM and they are the ones we want to work with. On my 92, the primary fan relay ground side of the signal circuit is green and the secondary one is blue with a white stripe. I unwrapped these two from the harness wrap so I could work with them. There is a very convenient ground just aft and below the fan relays. If you choose to put your switches in the engine compartment, this is a good place to mount the switches. I placed my two switches in the center console inside the cockpit. I never used the cup holder so I removed the rubber lining and fabricated a switch panel that fit right over the cup holder. That way I could cover the switches with the lid that slides in and out. I used the ground wire that is part of the accessory plug in the console to connect to one side of the switches. Then, using colored wires for identification, I ran the two wires from the switches to the engine compartment. Yes, I removed the lower trim panel, to gain access to the grommet that holds the hood release cables which is where I ran the wires through the fire wall. (Hardest part of the project) Now, just make the connections, primary ground side signal wire splice wire to switch. Then, secondary signal wire to the other switch. I soldered these connections and taped very well and stuffed them back into the harness wrap. Reconnect the battery and turn the key on. Turn the newly installed primary cooling fan switch on and you should hear or see the primary fan come on. Try the secondary switch also. You’re done! A few notes about the use of this modification, These fans are high draw items and will run your battery down if you turn them on and forget them. At the track, I’d use your tow vehicle and a set of jumper cables so you won’t let “Murphy's Law” get you. For normal driving, turn them off once you are going into cruise mode. This mod along with the electric water pump allows you to keep the C-4 a lot cooler.
