Can someone plz guide me on the working sequence of bother radiator fans. I think there are acting up. So much on this matter on so many forums, but to be frank there a bit confusing. Car is a OCTI VRS 

What year is the car?

It's a 2003 mk1 with AC

OK, well as far as I can see, both fans are wired in parallel, and both are two-speed. So if coolant temperature gets above the first temperature threshold of the radiator thermoswitch both should come on at low speed. If the coolant temperature continues to rise and exceeds the threshold for high speed fan function, both should accelerate to high speed.

When A/C is on, the fans are governed by refrigerant pressure also, low speed being triggered at one pressure, high speed at another. On (VAG group) cars I'm familiar with, the thresholds are 9 bar at G65 sensor for low speed, 16 bar for high speed. In all cases both fans should do the same thing at the same time.

 

What are yours doing?

Right now only the small one is triggered when the a/c is On and also when the temp climbs to 90. Not sure if it is running fast or slow. I tried giving direct battery current to the pins of the big fan but no movement noticed.

 

7 hours ago, skoda5232 said:

Right now only the small one is triggered when the a/c is On and also when the temp climbs to 90. Not sure if it is running fast or slow. I tried giving direct battery current to the pins of the big fan but no movement noticed.

Well, that's how the fans on mine work (1.9TDi with Climatronic). I've never got it hot enough to get a "demand fast" signal for the fans.

56 minutes ago, KenONeill said:

Well, that's how the fans on mine work (1.9TDi with Climatronic). I've never got it hot enough to get a "demand fast" signal for the fans.

 

What, only the small fan coming on? What year is yours @KenONeill?

Pulled the damn thing out and to my surprise one of the carbon brush was stuck due to dust, cleaned all the much up and now it looks OK. The 1ohm resistor looks fine so no prob with the low speed setup also I guess. But now I have to find heatsink paste to bond the resistor to the motor caseing.

Good work!

 

Reminds me of a comedy incident while fixing my Polo fans. Initially, the small fan (single speed on mine) was working, but the main fan wasn't working at low speed, but was at high speed. After fitting an external resistor for the main fan, I discovered when testing it that now the main fan started up OK but the small one didn't any more! 

Turned out that - following a similar route to what you took - two opposite brushes out of the four (like the first image here, except in that pic two adjacent brushes look stuck!) on the small fan were stuck, held away from where they needed to be by dust/debris like you found. When the main fan wasn't starting up, this still worked, but with the local voltage dip (shared wiring from fan control unit) of the main fan coming on, the small fan no longer worked.  Freeing those two brushes had everything back working as designed.

Edited 14 February, 20197 yr by Wino

Did a detailed check, I think one of the brush holders have overheated and started melting the brush housing anyway will fix it back and give it a go.

Fixed it all back and the fan is working ok though a bit noisy.. Meanwhile broke a coolant line while fixing it all back... My bad..