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Greg A
Greg A, Master Troubleshooter
Category: Buick
Satisfied Customers: 8914
Experience:  Working with Electronics & Cars for 25+ Years
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2000 Buick century: 3.1L - coolant fans do not turn..jump..voltage

Resolved Question:

2000 Buick Century 3.1L - coolant fans do not turn on as temperature gauge rises almost to red including when putting the A/C on Max. I plan to jump the fan motors from the hot on the battery and then ground the motors to see are working. Pull the 3 fan relays and check to see if there is voltage going to them (Any idea how many ohms the the relays should read at on a multi meter when good?). Test the coolant temp sensor to see if it's closing the circuit with volt meter when fully warm. Am I going in the right direction? Is this a common issue with this car?
Submitted: 8 years ago.
Category: Buick
Expert:  Greg A replied 8 years ago.

Hello & Welcome,


Can you tell if the cooling fans are coming on at all (like when the AC is switched on?



Customer: replied 8 years ago.
No, the fans do not come on at any time under any condition.
Expert:  Greg A replied 8 years ago.

OK - thanks.


Let me send along the schematic of the system so that you can do the basic tests first. That would be to check (with the meter) that the fuses are OK. Make sure power is making it to both sides of each fuse as the test.


Your plan to apply power and ground directly to the fan motor connectors is a good one, to make sure that each fan works.




As you might be able to tell, the PCM is what controls the relays, which in turn control the fans. I will also see if I can grab the description of the system and send it to you.


Please let me know what you find.


Thanks, XXXXX

Greg A and other Buick Specialists are ready to help you
Expert:  Greg A replied 8 years ago.

Hi again,


Here is the description of the system.


Engine Cooling Fan Description - Electric

The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.



The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the powertrain control module (PCM). The PCM turns the cooling fan ON by grounding the coil of the cooling fan relays when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.

Power for the cooling fan motors are supplied through Maxifuses®. The cooling fan relays are energized when current flows from the fuses in the Underhood Accessory Wiring Junction Block , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.


I hope this helps. Please let me know if you need more information.


Thanks, XXXXX