Low speed fans not coming on

RYAN TRACEE

MEMBER
2000 VOLKSWAGEN JETTA
2.0L
4 CYL
2WD
MANUAL
87,000 MILES

Fans will not come on. Here s what I have done thus far:
Changed coolant temperature sensor.
Manually verified that fans come on by jumping terminals at fan switch, low speed with no key, high speed with key on.
Checked two fuses on battery fuse box.
High speed fans come on when running AC.
Water leak passenger side possibly coming from water pump, I am leaning towards shattered impeller but top hose is warming up and I can feel water traveling, I would not think that would keep my fans from coming on, just the opposite.
Can someone point me in the right direction for my next step? Is there a separate fan relay under my dash I should be looking at? Aside from the control module?

4 Replies

JIS001

MECHANIC
3,411 POSTS

The propeller on the water pump is plastic and do fail. When they fail it would give symptoms of a bad thermostat. Since the coolant temperature sensor is used to signal the fans on, if the coolant is not flowing properly then the lower hose will not get hot enough to turn the fans on.

Since the water pump is starting to leak, I would recommend you start with replacing the water pump first and let us know if that solves the issue with the cooling fans.

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Friday, May 11th, 2018 AT 9:56 PM

RYAN TRACEE

MEMBER
9 POSTS

I was afraid you were going to say that, lol. Thank you, I will report back here with outcome.

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Friday, May 11th, 2018 AT 10:35 PM

JIS001

MECHANIC
3,411 POSTS

I know, I would cringe also when doing T-Belts on a VW as well, LOL.

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Friday, May 11th, 2018 AT 11:08 PM

F4I_GUY

MECHANIC
3,302 POSTS

For future reference there is a quick way to determine if the water pump is working.
Open the rad cap, there is a single coolant hose at the very top of the coolant bottle.
Disconnect this hose and place it into the coolant bottle (this is because coolant should be flowing out of it soon).
Have a helper start the engine and rev to 3,000 rpm's while you hold the small hose pointing into the coolant bottle.
While the engine is being revved, pressurized coolant should be flowing out of this hose and into the bottle.
If there is no, or very little coolant the water pump, as previously mentioned, has failed

Another item you might want to check if the problem persists, is the fan control module located under the battery tray. Very common failure point with A/C and coolant fan issues.

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Saturday, June 9th, 2018 AT 10:42 AM