Cooling Fan Switches
Thread Starter
Cruising
Joined: Jul 2005
Posts: 10
Likes: 0
From: Ewing KY
Cooling Fan Switches
I am relative new to the forum. I purchased a '94 LT1 about six months ago. It is practictly all stock and runs great. I know that this subject gets a great deal of attention and I do not have the knowlege or experience to form a concrete conclusion on it. I live in central Kentucky and the summers are very hot and humid, and when I stop or am in heavy traffic my engine temp raises to 220+. I usually drive with the windows down and the AC may be on or off. If it is off I turn it on to get both cooling fans running and this helps in preventing the temp from raising as fast.
I would like to add two switches in the driver compartment to manually turn the fans on when I need additional cooling. I plan to install two more relays to make it a clean installation. I would like to know how to get the wiring thru the firewall and where to pick up the voltage. The switches I purchased contain LEDs to indicate when they are on. They switch 12V to the end device and are rated at 30 Amp DC. In other words, I cannot switch the ground... only the Hot.
The only reason I am doing this is because the engine runs at 194 to 197 driving at 55 mph and I would like to keep the temp about the same in traffic.
I would like to add two switches in the driver compartment to manually turn the fans on when I need additional cooling. I plan to install two more relays to make it a clean installation. I would like to know how to get the wiring thru the firewall and where to pick up the voltage. The switches I purchased contain LEDs to indicate when they are on. They switch 12V to the end device and are rated at 30 Amp DC. In other words, I cannot switch the ground... only the Hot.
The only reason I am doing this is because the engine runs at 194 to 197 driving at 55 mph and I would like to keep the temp about the same in traffic.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
First, you won't keep your coolant temp in the summer at 195-197 when stopped or under 35 mph even with the fans on, the radiator is not big enough and the car was never designed to maintain the opening temp of the thermostat under these conditions. It will help some to turn on the fans when you know you are going to be stopped.
You only need a small switch to switch each fan relay coil terminal to ground to turn on each fan. You do not have to use any 30 amp switches or additional relays, nor do you need a switch with an LED on it. I don't know why you insist on switching 12v to the fan motor when you only need to turn on the fan relay through its low current relay coil! The switch wires can be passed through the rubber grommet on the front of the drivers door that the door wires go through. The wires are then inside the cockpit.
You only need a small switch to switch each fan relay coil terminal to ground to turn on each fan. You do not have to use any 30 amp switches or additional relays, nor do you need a switch with an LED on it. I don't know why you insist on switching 12v to the fan motor when you only need to turn on the fan relay through its low current relay coil! The switch wires can be passed through the rubber grommet on the front of the drivers door that the door wires go through. The wires are then inside the cockpit.
Thread Starter
Cruising
Joined: Jul 2005
Posts: 10
Likes: 0
From: Ewing KY
Thank you for this information. My reasoning for adding the new relays was to keep from feeding back into the control module when I turn the fans on. The switches are nice looking and easy to mount and only cost $5 at walmart.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
What lights the switches? The current through them? (12V vs ground current doesn't matter in this case)
You don't even need two switches, one DPST will work.
I don't think the control module is capable of receiving backfeed from the fans. It doesn't use "proof" points on them like it does on the fuel pump circuit.
Here's my how-to for my 85, yours should still be similar, except for relay locations, maybe wire colors.
http://webpages.charter.net/khasting...noverride.html
You don't even need two switches, one DPST will work.
I don't think the control module is capable of receiving backfeed from the fans. It doesn't use "proof" points on them like it does on the fuel pump circuit.
Here's my how-to for my 85, yours should still be similar, except for relay locations, maybe wire colors.
http://webpages.charter.net/khasting...noverride.html
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Centralcoasters tip is a good one but the I think the 85's relays were different so this may help.
You dont need extra relays or even a different 12v source. What you need to do is determine what terminals on your 94's relays are grounded by the ECM when AC high pressure switch or CTS tells ECM to activate fans. Then wire a ground to switch(s) and tap into that wires location on relay(s). When you flip the switch the relays think the ECM is grounding them which causes them to switch the 12v that they are holding at bay to the fan(s). There is no chance of overload or feedback, It's no different than when your AC or coolant temp sensor tells ECM to activate fans via relays by grounding.
I wrote a tech tip on this but keep in mind that the relays discussed are in my 1990 and not a 94, but the relays part #'s may be the same and are listed in the tech tip. Hope this helps. Good luck.
https://www.corvetteforum.com/techti...=282&TopicID=2
You dont need extra relays or even a different 12v source. What you need to do is determine what terminals on your 94's relays are grounded by the ECM when AC high pressure switch or CTS tells ECM to activate fans. Then wire a ground to switch(s) and tap into that wires location on relay(s). When you flip the switch the relays think the ECM is grounding them which causes them to switch the 12v that they are holding at bay to the fan(s). There is no chance of overload or feedback, It's no different than when your AC or coolant temp sensor tells ECM to activate fans via relays by grounding.
I wrote a tech tip on this but keep in mind that the relays discussed are in my 1990 and not a 94, but the relays part #'s may be the same and are listed in the tech tip. Hope this helps. Good luck.
https://www.corvetteforum.com/techti...=282&TopicID=2
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Thread Starter
Cruising
Joined: Jul 2005
Posts: 10
Likes: 0
From: Ewing KY
Excellent article skateparkdave. I can see that I need to scrap the idea of switching the hot and stay with the design concept and switch the ground.
As I said earlier, I know there is a lot of discussion on this "overheating" thing and I see pros and cons both ways, so I look at it this way- This car is 11 years old and has 100k miles on it and has no fan over rides and is basically stock. Overheating has not affected it yet, so why should I think it will be a problem in the future.
Thanks again.
As I said earlier, I know there is a lot of discussion on this "overheating" thing and I see pros and cons both ways, so I look at it this way- This car is 11 years old and has 100k miles on it and has no fan over rides and is basically stock. Overheating has not affected it yet, so why should I think it will be a problem in the future.
Thanks again.
