Fan/Teamp Switch: I'm Confused
Thread Starter
Team Owner
Joined: Jun 2002
Posts: 21,510
Likes: 0
From: On a Wisconsin Death Trip
Fan/Teamp Switch: I'm Confused
Sorry - I found an answer to my question in Tech Tips.
Ok, I did a search and I'm still confused about this whole deal. The fan on my 87 comes on like it should but I don't know if the Aux fan comes on at all. The reson this started is I installed a 160-degree stat and want to put a low temp fan switch in. Here's where my confusion starts: Where is the switch for the main fan? What switch is located on the driver's side between number 1 and number 3 cylinders? The wire's been cut by someone on whatever switch is located between 1&3 on my car. :confused: :jester
[Modified by loiq, 7:01 PM 8/11/2003]
Ok, I did a search and I'm still confused about this whole deal. The fan on my 87 comes on like it should but I don't know if the Aux fan comes on at all. The reson this started is I installed a 160-degree stat and want to put a low temp fan switch in. Here's where my confusion starts: Where is the switch for the main fan? What switch is located on the driver's side between number 1 and number 3 cylinders? The wire's been cut by someone on whatever switch is located between 1&3 on my car. :confused: :jester
[Modified by loiq, 7:01 PM 8/11/2003]
Burning Brakes
Joined: Nov 2001
Posts: 1,189
Likes: 2
From: Austin TX
Re: Fan/Teamp Switch: I'm Confused (loiq)
I can't speak exactly to your '87, but from the '85 wiring diagrams there
is only one fan switch. The ECM controls the main fan based on coolant
temp, and if the car only
has one fan (no aux fan) then the switch will also turn the fan on independent
of the ECM if the engine gets hot enough. The ECM should always kick it on
first though, so this must be a safety backup. On cars with two fans, the ECM
is the only thing that controls the main fan and the switch is the only thing
that controls the aux fan. The main fan will come on first, and if the temp
continues to rise, then the aux fan kicks on at a higher temp.
This lets the factory build the engines the same (with one switch) for
either fan option.
Hope that helps. I imagine the '87 is the same.
edit - And I'm pretty sure the fan switch is on the passenger side between
6 & 8. On the drivers side between 1 & 3 I'm pretty sure is actually a temp
sending unit for a gauge on the dash, and there is another temp sender
in the front of the intake for the ECM.
Dan
[Modified by danno85, 1:06 PM 8/11/2003]
is only one fan switch. The ECM controls the main fan based on coolant
temp, and if the car only
has one fan (no aux fan) then the switch will also turn the fan on independent
of the ECM if the engine gets hot enough. The ECM should always kick it on
first though, so this must be a safety backup. On cars with two fans, the ECM
is the only thing that controls the main fan and the switch is the only thing
that controls the aux fan. The main fan will come on first, and if the temp
continues to rise, then the aux fan kicks on at a higher temp.
This lets the factory build the engines the same (with one switch) for
either fan option.
Hope that helps. I imagine the '87 is the same.
edit - And I'm pretty sure the fan switch is on the passenger side between
6 & 8. On the drivers side between 1 & 3 I'm pretty sure is actually a temp
sending unit for a gauge on the dash, and there is another temp sender
in the front of the intake for the ECM.
Dan
[Modified by danno85, 1:06 PM 8/11/2003]
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Fan/Teamp Switch: I'm Confused (loiq)
I own an 87. The main fan is controlled by the ECM from temp info from the sender under the MAF which is also used for a/f etc. The main fan comes on at 228 F. The aux fan comes on at 238 F from a thermostatic switch between cylinders 1 and 3. The temp sender between cylinders 6 and 8 operates ONLY the dash temp gauge.
You can install a small toggle switch to ground the green/wh wire on the fan relay and manually turn on the fan at will. You can install a memory chip with the main fan turn on temps different than factory. A 160 stat will do nothing for lowering your summertime coolant temps as it will be wide open and have NO control of the coolant temp.
I cleaned out the debris in my radiator, replaced the water pump with a Stewart pump and installed a manual fan switch. The higher flow Stewart made the most difference.
You can install a small toggle switch to ground the green/wh wire on the fan relay and manually turn on the fan at will. You can install a memory chip with the main fan turn on temps different than factory. A 160 stat will do nothing for lowering your summertime coolant temps as it will be wide open and have NO control of the coolant temp.
I cleaned out the debris in my radiator, replaced the water pump with a Stewart pump and installed a manual fan switch. The higher flow Stewart made the most difference.
Thread Starter
Team Owner
Joined: Jun 2002
Posts: 21,510
Likes: 0
From: On a Wisconsin Death Trip
Re: Fan/Teamp Switch: I'm Confused (jfb)
jfb,
I'm planning on installing the lower temp fan switch (from MAD) in place of the Aux fan switch between 1&3 and this will turn both fans on at 200 degrees overriding the ECM, at least this is how I understand it. This should make my 160-degree stat work. I thought about going the manual switch route but I'm lazy and the wife sometimes drives the car - she likes things all set up and ready to go.
[Modified by loiq, 7:37 PM 8/11/2003]
I'm planning on installing the lower temp fan switch (from MAD) in place of the Aux fan switch between 1&3 and this will turn both fans on at 200 degrees overriding the ECM, at least this is how I understand it. This should make my 160-degree stat work. I thought about going the manual switch route but I'm lazy and the wife sometimes drives the car - she likes things all set up and ready to go.
[Modified by loiq, 7:37 PM 8/11/2003]
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Fan/Teamp Switch: I'm Confused (loiq)
Even with both fans on, in summer temps and below 35 mph, the C4 radiator is not big enough to transfer heat fast enough to maintain 160 F. Your 160 thermostat will be wide open and the temperature will settle to the same temperature that your factory stat did (because it was wide open too). I own an 87 with 195 stat, and at stoplights in 90 F temp and my main fan on, temp goes to 200 and when I get underway it falls to 195. With the factory waterpump it would go to 210-220 and would take a much longer time to drop to 195. My Stewart waterpump with higher flow makes the most difference.
Burning Brakes
Joined: Jul 2002
Posts: 972
Likes: 0
From: Springdale AR
Re: Fan/Teamp Switch: I'm Confused (loiq)
jfb,
I'm planning on installing the lower temp fan switch (from MAD) in place of the Aux fan switch between 1&3 and this will turn both fans on at 200 degrees overriding the ECM, at least this is how I understand it. This should make my 160-degree stat work. I thought about going the manual switch route but I'm lazy and the wife sometimes drives the car - she likes things all set up and ready to go.
I'm planning on installing the lower temp fan switch (from MAD) in place of the Aux fan switch between 1&3 and this will turn both fans on at 200 degrees overriding the ECM, at least this is how I understand it. This should make my 160-degree stat work. I thought about going the manual switch route but I'm lazy and the wife sometimes drives the car - she likes things all set up and ready to go.
Thread Starter
Team Owner
Joined: Jun 2002
Posts: 21,510
Likes: 0
From: On a Wisconsin Death Trip
Re: Fan/Teamp Switch: I'm Confused (jtfrog)
Quote:
Even with both fans on, in summer temps and below 35 mph, the C4 radiator is not big enough to transfer heat fast enough to maintain 160 F. Your 160 thermostat will be wide open and the temperature will settle to the same temperature that your factory stat did (because it was wide open too). I own an 87 with 195 stat, and at stoplights in 90 F temp and my main fan on, temp goes to 200 and when I get underway it falls to 195. With the factory waterpump it would go to 210-220 and would take a much longer time to drop to 195. My Stewart waterpump with higher flow makes the most difference.
Yes, this is a concern of mine, but after cleaning the radiator and installing the 160-degree thermostat it is running cooler already even without the re-programmed fans. I know the thermostat isn't going to be a magic fix but it's a start. I'm going to see how far the stat and the re-programmed fans will take me. Yesterday it was about 80 degrees here and the car never got over 200 where before the cleaning and the stat it would have been up to 220 easy, so I'm happy with that. The most important thing is it actually cools down at highway speeds where before it would struggle to get below 200.
Even with both fans on, in summer temps and below 35 mph, the C4 radiator is not big enough to transfer heat fast enough to maintain 160 F. Your 160 thermostat will be wide open and the temperature will settle to the same temperature that your factory stat did (because it was wide open too). I own an 87 with 195 stat, and at stoplights in 90 F temp and my main fan on, temp goes to 200 and when I get underway it falls to 195. With the factory waterpump it would go to 210-220 and would take a much longer time to drop to 195. My Stewart waterpump with higher flow makes the most difference.
Yes, this is a concern of mine, but after cleaning the radiator and installing the 160-degree thermostat it is running cooler already even without the re-programmed fans. I know the thermostat isn't going to be a magic fix but it's a start. I'm going to see how far the stat and the re-programmed fans will take me. Yesterday it was about 80 degrees here and the car never got over 200 where before the cleaning and the stat it would have been up to 220 easy, so I'm happy with that. The most important thing is it actually cools down at highway speeds where before it would struggle to get below 200.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: May 1999
Posts: 1,478
Likes: 3
From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Re: Fan/Teamp Switch: I'm Confused (loiq)
loiq,
As has already been mentioned, the switch from MAD that installs between cylinder 1&3 will only turn on the aux. fan. It will not affect the main fan. I installed one in my 88 and it turns the aux. fan on at 205 and off at 195. Turning the aux. fan on early will make a difference since it will now start earlier and will stay on longer. It is a very easy and worthwhile upgrade.
Your 87 radiator is mounted the same as my 88 and if you have a free Saturday morning and a few hand tools I strongly recommend pulling the radiator and cleaning it. Clear all debris and wash it with some diluted Simple Green. That will drop temps another 10 degrees across the board. I used to see 235 all the time in traffic. Since installing a 180 thermo, the aux switch, and completely cleaning the radiator last year, I have yet to see anything above 217 no matter what the temp outside. Highway temps are always between 182 and 187 day or night.
As has already been mentioned, the switch from MAD that installs between cylinder 1&3 will only turn on the aux. fan. It will not affect the main fan. I installed one in my 88 and it turns the aux. fan on at 205 and off at 195. Turning the aux. fan on early will make a difference since it will now start earlier and will stay on longer. It is a very easy and worthwhile upgrade.
Your 87 radiator is mounted the same as my 88 and if you have a free Saturday morning and a few hand tools I strongly recommend pulling the radiator and cleaning it. Clear all debris and wash it with some diluted Simple Green. That will drop temps another 10 degrees across the board. I used to see 235 all the time in traffic. Since installing a 180 thermo, the aux switch, and completely cleaning the radiator last year, I have yet to see anything above 217 no matter what the temp outside. Highway temps are always between 182 and 187 day or night.
Burning Brakes
Joined: Jul 2002
Posts: 972
Likes: 0
From: Springdale AR
Re: Fan/Teamp Switch: I'm Confused (Mike_88Z51)
loiq,
As has already been mentioned, the switch from MAD that installs between cylinder 1&3 will only turn on the aux. fan. It will not affect the main fan.
As has already been mentioned, the switch from MAD that installs between cylinder 1&3 will only turn on the aux. fan. It will not affect the main fan.
The instructions that came with it said I couldn't do it, but I did it anyway and it worked.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Fan/Teamp Switch: I'm Confused (loiq)
loiq, since you have a 160 deg stat I suggest you use a 160 deg aux fan switch. HyperTech makes them and are available through Summit Racing.
You can then use my C4 Tech Tip to wire that switch to bring on both fans around the thermostat's operating range. This will give best overall operation.
You can then use my C4 Tech Tip to wire that switch to bring on both fans around the thermostat's operating range. This will give best overall operation.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Fan/Teamp Switch: I'm Confused (65Z01)
loiq, since you have a 160 deg stat I suggest you use a 160 deg aux fan switch. HyperTech makes them and are available through Summit Racing.
You can then use my C4 Tech Tip to wire that switch to bring on both fans around the thermostat's operating range. This will give best overall operation.
You can then use my C4 Tech Tip to wire that switch to bring on both fans around the thermostat's operating range. This will give best overall operation.
RACE ON!!!
PS. GM DID swap locations of the fan switch and the guage temp sending unit several times.
