'90 cooling fan adjustment?
Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
'90 cooling fan adjustment?
I recently had the thermostat and cap replaced but the car still almost reaches the cross hatched area on the coolant gauge before only one fan kicks on; the second does not turn on (passenger side). I read up a little on this and was wondering if there was some sort of adjustment to the cooling fans. Also, should I get a lower temperature thermostat? The dealership claimed that both fans engaged at the proper temps, but I think they lied because the temp is pushing 250 at idle. Cools down when driving
(Edit) I am aware that the vette normally operates at a higher temp. My concern is that only one fan turns on once I hit the red while i'm not moving. Didn't have this problem last year
(Edit) I am aware that the vette normally operates at a higher temp. My concern is that only one fan turns on once I hit the red while i'm not moving. Didn't have this problem last year
Last edited by escamilla; Jun 11, 2014 at 10:59 AM. Reason: too many replies for the extreme temp being normal
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
If you want to see both fans come on short Pin A to Pin B on the diagnostic connector located above the drivers right knee. Turn the ignition to On both fans should run.
The relays for the fans are fastened to the driverside of the radiator shroud. They are both the same so you can swap them around.
The relays for the fans are fastened to the driverside of the radiator shroud. They are both the same so you can swap them around.
Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
[QUOTE=Stang-etr96;1587100362]250 IS ABOUT RIGHT FOR THE SECOND FAN TO KICK ON....it comes on sooner if A/C is turned on. C4's run hot. Its an emission
°250 is touching the red. I think the secondary should come on at °230 and the primary at °205. A vehicles fans should come on before the red
°250 is touching the red. I think the secondary should come on at °230 and the primary at °205. A vehicles fans should come on before the red
Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
If you want to see both fans come on short Pin A to Pin B on the diagnostic connector located above the drivers right knee. Turn the ignition to On both fans should run.
The relays for the fans are fastened to the driverside of the radiator shroud. They are both the same so you can swap them around.
The relays for the fans are fastened to the driverside of the radiator shroud. They are both the same so you can swap them around.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
You need a scan tool to monitor the temperature of the Engine Coolant Temperature sensor. This is the sensor the ECM uses to turn on the fans.
It's screwed into the front edge of the intake manifold above the water pump. Has a two pin connector with a Yellow and Black wire going to it.
Shorting Pin A to B puts the ECM in a diagnostic mode.
If both fans turn on when you turn the ignition ON (Don't start the engine) it tells you the fans and the wiring for the fans are good. It also tells you the ECM can control both fans.
If the fans are good but not coming on at the correct temperature the Engine Coolant Temperature Sensor could be out of tolerance.
Example. If you used an ohm meter to measure the resistance of the sensor.
210F the resistance=185 ohms
160F the resistance=450 ohms
100F the resistance=1.8K ohms
70F the resistance=3.4K ohms
40F the resistance=7.5K ohms
20F the resistance=13.50K ohms
In general the Primary fan comes on around 226F
Secondary fan around 232F
Example: If the primary fan comes on when the temperature reaches 226F but the temperature continues to rise above 232F, the secondary fan will come on.
The fans are also controlled by the AC coolant fan switch. When the AC high pressure reaches 240 psi the fans will also come on..
The Coolant Temperature sender for the dash temperature gauge could also be out of tolerance. It's screwed into the passenger side head between the 6 and 8 spark plug. it has a single Dark Green wire going to it.
As for which fan is primary and secondary. I've heard people say the primary fan is on the left side and some people have said it's on the right side.
If you look at the fan relay socket.
Primary fan relay will have a Light/Blue/Black wire going to it.
Secondary fan relay socket will have a Blue/White wire going to it.
It's screwed into the front edge of the intake manifold above the water pump. Has a two pin connector with a Yellow and Black wire going to it.
Shorting Pin A to B puts the ECM in a diagnostic mode.
If both fans turn on when you turn the ignition ON (Don't start the engine) it tells you the fans and the wiring for the fans are good. It also tells you the ECM can control both fans.
If the fans are good but not coming on at the correct temperature the Engine Coolant Temperature Sensor could be out of tolerance.
Example. If you used an ohm meter to measure the resistance of the sensor.
210F the resistance=185 ohms
160F the resistance=450 ohms
100F the resistance=1.8K ohms
70F the resistance=3.4K ohms
40F the resistance=7.5K ohms
20F the resistance=13.50K ohms
In general the Primary fan comes on around 226F
Secondary fan around 232F
Example: If the primary fan comes on when the temperature reaches 226F but the temperature continues to rise above 232F, the secondary fan will come on.
The fans are also controlled by the AC coolant fan switch. When the AC high pressure reaches 240 psi the fans will also come on..
The Coolant Temperature sender for the dash temperature gauge could also be out of tolerance. It's screwed into the passenger side head between the 6 and 8 spark plug. it has a single Dark Green wire going to it.
As for which fan is primary and secondary. I've heard people say the primary fan is on the left side and some people have said it's on the right side.
If you look at the fan relay socket.
Primary fan relay will have a Light/Blue/Black wire going to it.
Secondary fan relay socket will have a Blue/White wire going to it.
Last edited by Hooked on Vettes; Jun 11, 2014 at 06:50 AM.
Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
[QUOTE=Hooked on Vettes;1587106692]You need a scan tool to monitor the temperature of the Engine Coolant Temperature sensor. This is the sensor the ECM uses to turn on the fans.
Thank you. That is very helpful
Thank you. That is very helpful
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Whats been posted is CORRECT.
Its YOU thats uncomfortable....
This is NOT an older car that ran at 160. Anywhere below 190 is BAD for a C4. I might even go as far as saying anything below 210....it MUST get that hot for at least a little while each time its driven....its NOT just emissions. ITS engine LIFE and longevity ! !
This is a modern, computer controlled engine that's DESIGNED to run at 200+. It needs to in order to be healthy.
The primary fan comes on at 228 and the 2nd is at 238+. Perfectly normal. The car is designed to MOVE to get its fresh air. You cannot defeat the engineering of a car without a front grill. Don't even try. It can't be done.
Now IF, you do a bunch of engine modifications and end up with eng tuning that needs a slightly lower operating temp, then that MUST be done in the COMPUTER. Its called the "tune". But you really do not want to go too far. The engine is designed to run and be healthy at 225* avg,. and perform well. If you notice, ALL big engines made today run in these exact same temp ranges....
There is a reason and its NOT all emissions. Its longevity.
If you live in an extreme climate like S. Az. or Nevada, then you need a larger radiator and a better fan. A modified engine that makes more heat, and makes it faster then has to have more of a heat exchanger. The stock engine and its exchanger are adequate.
A lower t-stat only allows the coolant to get hotter faster. Won't help the upper temps. That's a FALACY ! the t-stat only controls the MIN temp, NOT the max !
If the ambient temp is HOT then the coolant temp HAS to also be HOT.
its called "temp differential". For my particular engine, that's almost exactly 100 degrees. ie: 87 outside....eng wants to cruise at 187ish...+ or - 3*.
If its 112 out, engine tries to hang @ 212 as the norm or cruise temp.
This differential is "set" by the heat exchange rate, the ability to dump heat and how fast its replaced with more heat. Engine mods effect this as does the exchanger itself.
If you stick a HD radiator on there now, it will be more stable, BUT it will still try to go up in traffic when the a/c is running BECAUSE it has no frontal area for free flow air to enter...but it will cool instantly when you move again. The fans just help...its not designed to survive on fans alone. Vettes want to move...
Don't worry over this. Its normal You as a new vette owner have to change your way of thinking. C4 and the later models ALL RUN HOT and if you do the maint, you get way over 200,000 miles out of a hi-performance engine. That's UN-heard of in the muscle car era...
the reason? Because they now run HOT and that is how they last so long....Heat is the friend of your engine.
Also as a regular maint issue, you have to take the radiator shroud OFF and clean out the gap between radiator and condenser once every couple years. That collects debris and leaves and blocks airflow to the radiator. That CANNOT be accessed unless you pull the top radiator shroud.
There isn't really anything to change on the engine. The people/engineers that designed it might know what they were doing.
your car is normal.
if anything needs to be done,. clean out the shroud. INSIDE. Its an all day project.
Good luck !
Its YOU thats uncomfortable....
This is NOT an older car that ran at 160. Anywhere below 190 is BAD for a C4. I might even go as far as saying anything below 210....it MUST get that hot for at least a little while each time its driven....its NOT just emissions. ITS engine LIFE and longevity ! !
This is a modern, computer controlled engine that's DESIGNED to run at 200+. It needs to in order to be healthy.
The primary fan comes on at 228 and the 2nd is at 238+. Perfectly normal. The car is designed to MOVE to get its fresh air. You cannot defeat the engineering of a car without a front grill. Don't even try. It can't be done.
Now IF, you do a bunch of engine modifications and end up with eng tuning that needs a slightly lower operating temp, then that MUST be done in the COMPUTER. Its called the "tune". But you really do not want to go too far. The engine is designed to run and be healthy at 225* avg,. and perform well. If you notice, ALL big engines made today run in these exact same temp ranges....
There is a reason and its NOT all emissions. Its longevity.
If you live in an extreme climate like S. Az. or Nevada, then you need a larger radiator and a better fan. A modified engine that makes more heat, and makes it faster then has to have more of a heat exchanger. The stock engine and its exchanger are adequate.
A lower t-stat only allows the coolant to get hotter faster. Won't help the upper temps. That's a FALACY ! the t-stat only controls the MIN temp, NOT the max !
If the ambient temp is HOT then the coolant temp HAS to also be HOT.
its called "temp differential". For my particular engine, that's almost exactly 100 degrees. ie: 87 outside....eng wants to cruise at 187ish...+ or - 3*.
If its 112 out, engine tries to hang @ 212 as the norm or cruise temp.
This differential is "set" by the heat exchange rate, the ability to dump heat and how fast its replaced with more heat. Engine mods effect this as does the exchanger itself.
If you stick a HD radiator on there now, it will be more stable, BUT it will still try to go up in traffic when the a/c is running BECAUSE it has no frontal area for free flow air to enter...but it will cool instantly when you move again. The fans just help...its not designed to survive on fans alone. Vettes want to move...
Don't worry over this. Its normal You as a new vette owner have to change your way of thinking. C4 and the later models ALL RUN HOT and if you do the maint, you get way over 200,000 miles out of a hi-performance engine. That's UN-heard of in the muscle car era...
the reason? Because they now run HOT and that is how they last so long....Heat is the friend of your engine.
Also as a regular maint issue, you have to take the radiator shroud OFF and clean out the gap between radiator and condenser once every couple years. That collects debris and leaves and blocks airflow to the radiator. That CANNOT be accessed unless you pull the top radiator shroud.
There isn't really anything to change on the engine. The people/engineers that designed it might know what they were doing.
your car is normal.
if anything needs to be done,. clean out the shroud. INSIDE. Its an all day project.
Good luck !
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Thread Starter
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 0
[QUOTE=leesvet;1587106885]Whats been posted is CORRECT.
First of all, I think you don't really know what you're talking about because while driving the temperature is less than °190.
Second, I'm not a "new vette owner"
furthermore, the temperature is right on the red before the fan kicks on, and only one fan. It's never had this problem before. It started a couple times last year but now its every time it sits idol. Also, the radiator is clear
And lastly, I don't appreciate being patronized
First of all, I think you don't really know what you're talking about because while driving the temperature is less than °190.
Second, I'm not a "new vette owner"
furthermore, the temperature is right on the red before the fan kicks on, and only one fan. It's never had this problem before. It started a couple times last year but now its every time it sits idol. Also, the radiator is clear
And lastly, I don't appreciate being patronized
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
You can switch the fan ground signal to a lower temp cylinder head switch, or have you memcal (chip) reprogrammed to lower temps, and even use a lower temp t-stat. Lower temps also create less pressure. GM used the higher heat for improved burn at the expense of better performance. A cooler engine performs better.
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
Gauges on the 90 may be reading high as they were on my 90.
Primary fan starts @ 228 or anytime AC is selected. With AC off: Check radiator temp @ the top hose connection with a pyrometer when the primary fan starts. If temp is higher than 228 replace the fan sending unit located front / lower intake manifold.
Secondary fan on a 90 is triggered by AC high side pressure not coolant temp. IIRC AC high side pressure must exceed 260 psi(?) before the secondary fan will operate.
What I did: The fan relays always have 12V & operate via the ground circuit. Connect both fan relay ground wires together with a jumper wire. Both fans will operate @ turn on temp or when AC is in use. You may experience faster cabin cool down & colder vent temps. Additional air flow through the AC condenser = a more efficient system.
Good luck.
BTW: In traffic with AC on coolant temp is always mid gauge = where the stat opens.
Primary fan starts @ 228 or anytime AC is selected. With AC off: Check radiator temp @ the top hose connection with a pyrometer when the primary fan starts. If temp is higher than 228 replace the fan sending unit located front / lower intake manifold.
Secondary fan on a 90 is triggered by AC high side pressure not coolant temp. IIRC AC high side pressure must exceed 260 psi(?) before the secondary fan will operate.
What I did: The fan relays always have 12V & operate via the ground circuit. Connect both fan relay ground wires together with a jumper wire. Both fans will operate @ turn on temp or when AC is in use. You may experience faster cabin cool down & colder vent temps. Additional air flow through the AC condenser = a more efficient system.
Good luck.
BTW: In traffic with AC on coolant temp is always mid gauge = where the stat opens.
Last edited by Churchkey; Jun 11, 2014 at 09:07 AM.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Just for clarification:
In the 1990 model year both fans are controlled by the ECM. Primary is set at 107.75C (225.95F), secondary 113C (235.4F), and the secondary will also come on when a signal from the AC is received. A head switch may be substituted, but never came on the original car. The temp signal is received from the CTS at the front of the intake just below the fuel inlet.
In the 1990 model year both fans are controlled by the ECM. Primary is set at 107.75C (225.95F), secondary 113C (235.4F), and the secondary will also come on when a signal from the AC is received. A head switch may be substituted, but never came on the original car. The temp signal is received from the CTS at the front of the intake just below the fuel inlet.
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
[QUOTE=escamilla;1587107101]
welcome to the forum...
first..he does know what he's talking about....don't see the patronization..
if you search threads, you will see all new members complain about the temps in one form or another....everyone tries to help.... his posting was factual and imformative for many of us.... get a thicker skin and stay with us...you'll learn a lot...nobody writes that long a thread to patronize you....we all want to help and get help when we need it.
Paul
Whats been posted is CORRECT.
First of all, I think you don't really know what you're talking about because while driving the temperature is less than °190.
Second, I'm not a "new vette owner"
furthermore, the temperature is right on the red before the fan kicks on, and only one fan. It's never had this problem before. It started a couple times last year but now its every time it sits idol. Also, the radiator is clear
And lastly, I don't appreciate being patronized
First of all, I think you don't really know what you're talking about because while driving the temperature is less than °190.
Second, I'm not a "new vette owner"
furthermore, the temperature is right on the red before the fan kicks on, and only one fan. It's never had this problem before. It started a couple times last year but now its every time it sits idol. Also, the radiator is clear
And lastly, I don't appreciate being patronized
welcome to the forum...first..he does know what he's talking about....don't see the patronization..
if you search threads, you will see all new members complain about the temps in one form or another....everyone tries to help.... his posting was factual and imformative for many of us.... get a thicker skin and stay with us...you'll learn a lot...nobody writes that long a thread to patronize you....we all want to help and get help when we need it.
Paul
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
it is not....seems like they have given you enough information to check on why it isn[t.....if not, keep asking.... nobody is trying to argue with you...just help...I have a 85 with a different fan set up so i[m not much help ...just moral support...there are trouble shooting guides in the fsm for these types of problems....if you don't have one, check on e bay for the gm manual....Paul 
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
welcome to the forum...first..he does know what he's talking about....don't see the patronization..
if you search threads, you will see all new members complain about the temps in one form or another....everyone tries to help.... his posting was factual and imformative for many of us.... get a thicker skin and stay with us...you'll learn a lot...nobody writes that long a thread to patronize you....we all want to help and get help when we need it.
Paul
He comes across as a matter of fact when this argument is as old as time. A cooler intake charge equals more power. Hotter is more fuel efficient. The programming sees it as fully warmed at 170 degrees.
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
for what it's worth, I put in manual switches with a 160 t stat....later had it all tuned to come on at 175.....I always stay around 190....sometimes 200 in traffic in s fl a/c on....so I agree with Mr ***** but.......long winded or not, I appreciate every post that I can learn something about my car......you can condescend my *** off...as long as I learn something......woohoo:
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
Just for clarification:
In the 1990 model year both fans are controlled by the ECM. Primary is set at 107.75C (225.95F), secondary 113C (235.4F), and the secondary will also come on when a signal from the AC is received. A head switch may be substituted, but never came on the original car. The temp signal is received from the CTS at the front of the intake just below the fuel inlet.
In the 1990 model year both fans are controlled by the ECM. Primary is set at 107.75C (225.95F), secondary 113C (235.4F), and the secondary will also come on when a signal from the AC is received. A head switch may be substituted, but never came on the original car. The temp signal is received from the CTS at the front of the intake just below the fuel inlet.
Reference to condenser pressure in the 90 FSM page 6 B-1.
See 1990 FSM 8A supplement circuit operation description page
8A-31-3.
The only thing that is different than what I had posted before from memory is the fan turn on PSI which happens to be lower @ 190 PSI.
Racer
Joined: Jun 2014
Posts: 332
Likes: 1
So i am new to the vette world with my 94. My car runs really hot in traffice and town as well but fine on the highway. Noticed in town with ac on it stays cool fine but without it on it will not stay cool. From what i have gathered here it seems like my ac cooling fan is doing all the work and my primary isn't coming on at all. I have been under the hood waiting for it to come on and it never does even when car is in the red. I found the information here helpful and i am going to try to jumper the connections to see if the fans come on. If they don't please clarify for me jumping the 2 grounds on the relay will make the fans both fans come on when the ac calls but that wont help me a bunch unless the ac is on?