Hi fellas,

 

Do you have any idea if the main radiator fan(s) have multiple speeds or only one? 

I managed today to do a bit of logging while driving the car.
This is the graph after driving the car at about 3000-3500rpm in 2nd with outside temp of 20/25 Celsius. It looks pretty good imho.


The last one has been done after leaving the car idling in the sun for about 5 minutes.


Both graphs look ok. The fans are starting when the coolant gets at about 97.5 Celsius and are blowing til the temp drops to about 85. Should the fans have two speeds? Is there a way I can tell if those are blowing on the lowest or the highest setting? I saw that both of them were running each time. Is it normal?

If fan has only two wires going into it, it's a single speed, if three wires - two speed. On my phone just now so can't see graphs well, but switch on temp sounds about right for low speed.

Fans are shown as being in parallel on wiring diags so both should do same at same times if both have same number of speeds.

Edited 22 May, 201610 yr by Wino

Both fans have 3 wires..

When should the fans kick at each speed level? Is it based on engine load vs temp or only temp?

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Both your fans are twin speed then, and they should do the same as each other. There are only two relays in the Fan Control Module, one for low speed operation, one for high. You can test the two speeds by unplugging the big four-way connector from the underside of the module and shorting either the two smaller contacts (for low speed) or the two wider contacts (for high speed). Expect to see sparks (and use a thick bit of copper wire not a paperclip), especially on the high speed, as the surge current at switch on is pretty high.

 

The radiator thermoswitch is actually two switches, one kicks in when the coolant it is sampling exceeds 95C, switching on fan(s) at low speed. The other when it gets to 102C I think, putting fans on at high speed. Usually the first speed is enough to stop the temperature going higher, so the high speed rarely gets used unless there's a problem with the low speed operation (in the UK...).

In cars with AC, that module can turn on fans at both speeds too, I think, according to refrigerant pressure sensed by G65 (?). And possibly temperature info from engine coolant sensor (via CAN from engine ECU)?

In cars without AC, I think the only thing that brings the fans on is the radiator thermoswitch.

Edited 23 May, 201610 yr by Wino

So basically it should kick into high speed only if there would be something wrong with the low speed and this would happen only if the temp would exceed 102C ? Both fans should be working at the same time also ?

Here's a snapshot of a typical wiring diagram, with some annotations added to try to explain a bit. I've added a green 'wire' showing a link that is indicated by the track numbers in the rectangular boxes.

There are some variations on this diagram, with the thermoswitch sometimes directly carrying fan currents rather than just energising the relay coils by grounding their low sides. I think in those cases both fans are still in parallel, with links D167, 168 as below:

 

 

So if only one of the fans operates at low speed, the other one probably has a burnt out internal resistor. Can check by measuring resistance 'up' the relevant connector, T3i or T3u, pin 2 to pin 3.

hi guys new to this forum and would like to share my problem

 

 i have a skoda fabia 1.9tdi 2001 i recently checked the ac which needed a slight top up  and guess what the fans did not cut in when the ac

was turned on

so on further checking the fans by way of disconnecting  the main radiator fan connectors thats the two three wire plugs i hot wired the wires that

lead to the fans  by placing one wire from the earth of the battery to the brown that leads to the small radiator then another wire from the live of the battery to each of the remaining two needless to say both fans are inoperative on the low side that is stage 1

today i removed the small fan and pulled it apart

 

my findings are that the resistance is actually intact what has happened is the heat of sed resistance has melted the plastic around it and the heat had de soldered it 

i could of re soldered it back in again but the same thing would happen again  

:who puts a resistance in anywhere where it gets hot enough  to melt  plastic and solders it to the other side with no cooling not me thats for sure

so the fix take the resistance out altogether make good the melted plastic and re solder every connection i soldered a piece of wire between where the resistance was removed   place back together and checked again through the plug while still out of the car using the wire that i used to test and hey presto fan now works on FULL speed on both wires

now i can do the 1ome 100w risister mod which means both sides of the fan stage 1 and stage 2 both work an normal all i have done is put the resistance external instead of in the fan

 just thought i would share my experience 

 

alls well that ends well

 

kebe