Electric cooling fans will not turn on

Tiny
DEANLANDIS
  • MEMBER
  • 1998 BUICK CENTURY

Electric cooling fans will not turn on when engine gets too hot. I checked the fuses and relays. They are good. I replaced the CTS and it did not fix the problem. I did discover that if I disconnect the electrical connector to the CTS, the electric fans will turn on and stay on. I have left the connectors disconnected temporarily so that the engine does not over heat. In doing this, I've noticed a drop in gas mileage. Please help. Oh, the radiator fluid level is good.
Do you
have the same problem?
Yes
No
Sunday, October 3rd, 2010 AT 10:32 AM

24 Replies

Tiny
HMAC300
  • EXPERT
The reason your gas mileage dropped is you disconnect the cts and it doesn't control the fans. plug it back in. There are 3 relays not 2 and 2 large fuses. they all must be checked. I'm including a diagram. If it's not a relay, then you'll have to have a pro check it for a bad connection or shorted wire coming from or to the pcm....

Heres a guide on checking relays and one on testing wiring, they will help you figure this out

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

https://www.2carpros.com/articles/how-to-check-wiring


http://www.2carpros.com/forum/automotive_pictures/406719_relay_diag_1.jpg

Was this
answer
helpful?
Yes
No
+5
Sunday, October 3rd, 2010 AT 12:56 PM
Tiny
DOUGLASEBOGGS
  • MEMBER
How do you test the relays for the coolant fans
Was this
answer
helpful?
Yes
No
+10
Monday, September 17th, 2012 AT 3:06 PM
Tiny
JIMBO_KIRKO
  • MEMBER
  • 1999 BUICK CENTURY
  • 3.1L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 69,500 MILES
My cooling fans do not want to come on when the temp begins to climb, until it reaches an unsafe temperature range above normal. I have replaced the Temperature Sensor with no luck. The issue remains. The dual fans come on when the a/c is turned on, but still they will not come on due to engine temp until like I said, when engine reaches an unsafe temperature. My book shows 3 relays, Relay 1, relay 2 and Relay 3, they are identical, why does it need 3 relays for dual fans wired in conjunction and why wont they come on at the correct water temp?
Was this
answer
helpful?
Yes
No
+1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
First of all, temperature gauges are notoriously inaccurate. They are most useful when you know from plenty of experience what "normal" is, and you notice when something abnormal is occurring. Second, a lot of GM cars are designed for the fans to not turn on until coolant temperature gets well above the boiling point of water, 212 degrees F. A switching point if 220 degrees is common and acceptable. Third, there are usually two different coolant temperature sensors; one for the Engine Computer which controls the radiator fans, and one for the dash gauge. It's common to find a discrepancy between them. To know for sure if there really is a problem, you need a scanner to view live sensor data. That will show you the actual coolant temperature.

The reason for the multiple relays is you may have a high-speed relay and a low-speed relay, and there could be a third one that turns the fans on when the AC compressor turns on. The low-speed relay is used when the manufacturer wants less noise to be heard and lower air flow is sufficient. You may not hear the fan turn on low speed if the hood is closed.

Also, a scanner will allow you to command the relays to turn on and off. That will let you verify the circuitry is operating properly.
Was this
answer
helpful?
Yes
No
+2
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CSM1992
  • MEMBER
  • 1987 BUICK CENTURY
  • 83,000 MILES
I recently acquired a 1987 Century with the 2.5L engine. The car runs great however the cooling fan only runs with the A/C on. I checked a basic wiring diagram and find that the wire from the ECM to the fan is grn/yellow. There is a plug near the fan hanging in space that has two wires: grn and grn/yellow. The problem is I can't find a home for it. The plug that goes on the fan has a blk and blk/red wire and there are no other plugs. I even checked at the parts store to see if it had the wrong fan and no it apparently has the correct fan. Traced the black and red wire up the harness a bit looking for another plug but no luck. Any suggestions?
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
Does your temp gauge work?Also do you have a multimeter to do some testing?
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
Check the coolant fan switch located on upper left side of engine, at end of exhaust manifold. It has a Dark Green/White wire.
Was this
answer
helpful?
Yes
No
-1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CSM1992
  • MEMBER
I am an above average shadetree mechanic and have tools etc. The plug in question has grn and grn/yellow wires. The coolant temp sensor has one wire attached.
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
Post a pic of the connector showing it and where its located. The single wire is the gauge the two wires is the coolant temp sensor connector
Was this
answer
helpful?
Yes
No
+1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
HOMER2210
  • MEMBER
  • 1997 BUICK CENTURY
  • 6 CYL
Are the cooling fans supposed to run all the time or just intermittenly? I notice that they do not run at idle, but after driving I stopped and ran out quickly to check and they were moving.

Also, I just had my water pump replaced, afterward the low coolant light came on, I filled the radiator up and the light went of but still comes on. Today when I got to work I opened the hood and felt the radiator hoses, which were extremely hot, I removed the radiator cap and I could hear air escape and then antifreeze flow/gurgle into the radiator. My temp gauge did not go up saying the engine was hot, but I think that antifreeze was not flowing, there must have been air in there from my first fillup of antifreeze. I bought a new thermostat and am replacing that tonight. Thoughts?
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Try the thermostat and bleeding it out and see what happens start here, also check and test the coolant temperature sensor-
Was this
answer
helpful?
Yes
No
-1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
It says the temp sensor is on left side of engine bellow coolant outlet.
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
The cooling fan come's on at 212 degree's here is a description of the fan operation.I also posted the draining and refilling of the coolant along with bleeding the air out of it. Let me know what happens after your done with thermostat replacement and the bleeding of the air in the coolant.

WARNING: An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.

All vehicles use two 360 mm (14.2 inch) fans to aid air flow through the radiator/condenser. Each fan is driven by an electric motor and is attached to the radiator. Electrical motor size varies with engine option. The fan motors are activated by a coolant temperature switch. A transducer can also activate the circuit, depending upon A/C request or A/C compressor head pressure to the condenser.

NOTE: This procedure significantly increases the amount of used coolant and diluted hazardous waste.

DRAINING

Park the vehicle on a level surface.
Remove and clean coolant recovery reservoir.
Remove the radiator cap when the engine is cool by:

Slowly rotating the cap counterclockwise to detent. Do not press down while rotating pressure cap.
Wait until any residual pressure (indicated by a hissing sound) is relieved.
After all hissing stops, continue to rotate counterclockwise until the cap is removed.

NOTE: Recover coolant and store in a used coolant holding tank and submit the used coolant for recycling on a regular basis. This procedure significantly increases the amount of used coolant and diluted hazardous waste.

Place drain pan under vehicle to collect all drained coolant.
Open the radiator drain valve located at the bottom of the radiator tank. For procedures requiring the cooling system to be partially drained, opening the radiator drain valve should provide sufficient draining and no further actions should be necessary.

Open the air bleed vent(s): Open the air bleed vents on the thermostat housing and above water pump. The air bleed vents should be opened two to three turns.

Remove the engine block drains: Remove both engine block drains. The front engine block drain is located between the starter and the engine oil filter. The rear engine block drain is located in the same area in the center of the block.
Disconnect inlet hose to engine oil cooler (if equipped).
Allow the coolant to drain completely.

WARNING: Dispose of used coolant in a proper fashion, i.E, in a used coolant holding tank. NEVER POUR USED COOLANT DOWN THE DRAIN! Ethylene glycol antifreeze is a very toxic chemical; disposing of it into the sewer system or ground water is both illegal and ecologically unsound!

REFILLING

Close the radiator drain valve. Reinstall all engine block drains.
Install the coolant recovery reservoir. Flush the reservoir with clean water, drain and reinstall.
Slowly fill the cooling system through the radiator neck using the following procedure:

If the coolant system has been flushed, first add 100 percent ethylene glycol in the amount listed for the appropriate engine application. Then slowly add clean water to the system until the level of the coolant mixture has reached the base-of the radiator neck. Wait for two minutes and recheck the level of the coolant mixture, add clean water if necessary to restore the coolant mixture level to the base of the radiator neck.
When refilling the engine cooling system, add three engine coolant supplement sealant pellets, GM P/N 3634621 or equivalent, and GM approved new Ethylene Glycol Coolant DEX-COOL GM P/N 9985809.
If the cooling system is being refilled ONLY (no flush), a 50 percent ethylene glycol and 50 percent clean water mixture should be used to fill the system. Fill the system until the level of the 50/50 mixture has reached the base of the radiator neck. Wait two minutes and recheck the level of the coolant mixture, add a 50/50 ethylene glycol/water mixture as necessary to restore the coolant mixture level to the base of the radiator neck.

Install the radiator cap making certain the arrows line up with the overflow tube.
Close all air bleeds. DO NOT over torque the air bleed valve. The air bleed valve is made out of brass.
Fill the coolant reservoir with a 50 percent ethylene glycol and a 50 percent clean water coolant mixture. The proper amount of this mixture to be installed into the coolant reservoir is listed below:

Add 0.65 liters (0.68 quarts) of a 50/50 mixture of ethylene glycol and clean water to the coolant recovery reservoir.

CAUTION: The low coolant indicator lamp may come on after this procedure. After operating the vehicle so that the engine heats up and cools down three times. If at any time the "TEMP" warning indicator comes on, immediate action is required.
Was this
answer
helpful?
Yes
No
-1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CADIEMAN
  • MEMBER
Find the fan relay try swapping the relay with another 1.I would replace the coolant sensor that is what controls the fan oper. It grounds the fan relay to turn the fans on when the a/c is off.
Was this
answer
helpful?
Yes
No
-1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
HOMER2210
  • MEMBER
Ok that explains why I cant see the fans running at idle. When I drove the car home yesterday it seemed fine, temp did not go up and low coolant light did not come on, I think that the problem was just that there was that air had gotten in there and when I opened the radiator cap and release the pressure and it filled back up it fixed it. Thanks for you help.
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
If the fan comes on with the ac I would say the fan relay is working wouldn't you cadieman?
Was this
answer
helpful?
Yes
No
+1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
Your welcome keep us posted on how it turns out or if you have anymore questions.
Was this
answer
helpful?
Yes
No
+1
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CADIEMAN
  • MEMBER
Yes but the coolant temp. Sensor tells the cpu when to turn the fans on when the temp. Is to high. The fans are turned on auto. As soon as u turn the a/c on.
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
SATURNTECH9
  • MEMBER
Correct but the same relay is used to turn the fan on at the correct temp or when the ac is turned on. So when you said to check the relay that's why I said what I said.
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)
Tiny
CADIEMAN
  • MEMBER
I was thinking the a/c grounds the relay directly from the a/c head when turned on. When u let the sensor ground the relay thats from the temp. Sensor. So u have 2 circuts controlling the fan funshion by grounding the relay.1 is the cts and the other is the a/c head. Seeya tomarrow im falling asleep. Ltr
Was this
answer
helpful?
Yes
No
Monday, June 24th, 2019 AT 6:16 PM (Merged)

Please login or register to post a reply.

Sponsored links