Radiator fan constantly running

RZX

A2OC Donor
Hello everyone
My radiator fan is constantly running even when the car is turned off and no key in the ignition, any ideas please.
It is a 2001 1.4 petrol.

Thanks in advance.
 
I think the fan controller will have failed, probably due to water ingress. This is the box at the front of the engine bay mounted at the top of the radiator.
Try one of the members who breaks cars, maybe @A2Steve or @Clackers. In the meantime, to prevent a flat battery, you can disconnect the heavy current connectors on top of the controller. Do this by pushing down (to compress the seals) then simultaneously press the latch towards the wires and switch from pressing down to wiggling up.
You should reconnect before driving if there is any chance of getting stuck in a traffic jam otherwise the engine will overheat with no fan.
Good luck,
Matt


Sent from my iPhone using Tapatalk
 
I think the fan controller will have failed, probably due to water ingress. This is the box at the front of the engine bay mounted at the top of the radiator.
Try one of the members who breaks cars, maybe @A2Steve or @Clackers. In the meantime, to prevent a flat battery, you can disconnect the heavy current connectors on top of the controller. Do this by pushing down (to compress the seals) then simultaneously press the latch towards the wires and switch from pressing down to wiggling up.
You should reconnect before driving if there is any chance of getting stuck in a traffic jam otherwise the engine will overheat with no fan.
Good luck,
Matt


Sent from my iPhone using Tapatalk
Thank you, we were trying to disconnect the conectors but obviously doing it wrong, so will try in the morning.
Thanks again.
 
Andy, that’s an excellent point. See clip, it’s 40A if this is correct for year and model-non climate could be different.
9c8d69bfe4ac5b72e379e532833e29f0.jpg



Sent from my iPhone using Tapatalk
 
Glad to hear you are back up and running.

As I’ve suffered 2 failures myself, and also I’m an electronic engineer, I wondered 3 things:

A) why the water gets in (if it does)?
B) is repair possible?
C) when the supply of used units will begin run out?

Answering these in a random order hopefully without rambling on excessively:

The answer to (C) will of course be when the rate of A2s getting broken up for parts begins to exceed the rate of failures of the module of cars still in the road. Since the module is an A2-specific part (8Z0 prefix part number), presumably no other models fan controller module can be used, though it would’ve interesting to know other views on this.

As to (A), I disassembled both failed units.

To do this, lift the ends of the label showing the connectors and remove the 4 Torx screws from the plate underneath. This allows the plate to be levered out, destroying the mastic seal. Then, underneath is a spring steel clamp which clamps 3 transistors to casting rib as a heatsink to cool them. There is a thermal pad for electrical insulation (but thermal conduction) between the transistor tabs and the casting rib. The clamp can be levered up This then allows the plastic clips around the top to be peeled up gently a few at a time, wedging with toothpicks or similar until the whole connector/PCB can be slid out.

The mastic plate seal is pretty good, I didn’t see this as a route in for water. I think the only other routes in are:
1) Seal failure around the wires
2) Seal failure between the on-wire connector housing and the plastic part of the case.
3) Breakage of connector latches, resulting in no seal compression.
4) Seal failure between the plastic and metal parts of the case.
5) Porous casting.
6) Effect of pressure washing engine???

Both of my failed units had clear signs of water in the bottom of the case casting, with corrosion to the PCB traces and surface mount resistors and ceramic capacitors. I couldn’t see any issues with the connectors or seals in either module of mine, so it is still a mystery.

As to question (B), although I could have attempted repair, I decided to get a used one in both cases because of reasonable cost currently, and also the risk of overheating due to no fan operation leading to other much more expensive problems like a blown heat gasket if my repair did not last.

@RZX I’m not sure if you’re interested in disassembling your failed module, (no worries if not), but if you are able to get it apart it would be good to know if it had also suffered water ingress.

All the best,
Matt


Sent from my iPhone using Tapatalk
 
Glad to hear you are back up and running.

As I’ve suffered 2 failures myself, and also I’m an electronic engineer, I wondered 3 things:

A) why the water gets in (if it does)?
B) is repair possible?
C) when the supply of used units will begin run out?

Answering these in a random order hopefully without rambling on excessively:

The answer to (C) will of course be when the rate of A2s getting broken up for parts begins to exceed the rate of failures of the module of cars still in the road. Since the module is an A2-specific part (8Z0 prefix part number), presumably no other models fan controller module can be used, though it would’ve interesting to know other views on this.

As to (A), I disassembled both failed units.

To do this, lift the ends of the label showing the connectors and remove the 4 Torx screws from the plate underneath. This allows the plate to be levered out, destroying the mastic seal. Then, underneath is a spring steel clamp which clamps 3 transistors to casting rib as a heatsink to cool them. There is a thermal pad for electrical insulation (but thermal conduction) between the transistor tabs and the casting rib. The clamp can be levered up This then allows the plastic clips around the top to be peeled up gently a few at a time, wedging with toothpicks or similar until the whole connector/PCB can be slid out.

The mastic plate seal is pretty good, I didn’t see this as a route in for water. I think the only other routes in are:
1) Seal failure around the wires
2) Seal failure between the on-wire connector housing and the plastic part of the case.
3) Breakage of connector latches, resulting in no seal compression.
4) Seal failure between the plastic and metal parts of the case.
5) Porous casting.
6) Effect of pressure washing engine???

Both of my failed units had clear signs of water in the bottom of the case casting, with corrosion to the PCB traces and surface mount resistors and ceramic capacitors. I couldn’t see any issues with the connectors or seals in either module of mine, so it is still a mystery.

As to question (B), although I could have attempted repair, I decided to get a used one in both cases because of reasonable cost currently, and also the risk of overheating due to no fan operation leading to other much more expensive problems like a blown heat gasket if my repair did not last.

@RZX I’m not sure if you’re interested in disassembling your failed module, (no worries if not), but if you are able to get it apart it would be good to know if it had also suffered water ingress.

All the best,
Matt


Sent from my iPhone using Tapatalk
Hello Matt
Yes indeed Martin is interested in taking the failed unit apart, I will report his findings.
Thanks again for your help in this matter.

Mandy
 
I wouldn’t worry too much about supply. I get asked for one every few months at most and have 3 on reserve already but could easily up that number quite quickly should the demand increase.
 
I wouldn’t worry too much about supply. I get asked for one every few months at most and have 3 on reserve already but could easily up that number quite quickly should the demand increase.
Add to that the 7 or 8 I have on my shelf and we should be able to supply for a few years yet!
 
Fan controller dismantled and yes obvious signs of water ingress, the seal seemed to in place OK.

Took the car out today with the roof open as the sun was shining, went to my usual parking area to find a fellow A2, no sign of the owner though.
 

Attachments

  • IMG_20210518_174210~2.jpg
    IMG_20210518_174210~2.jpg
    1.2 MB · Views: 156
  • IMG_20210518_181216.jpg
    IMG_20210518_181216.jpg
    1.7 MB · Views: 158
  • IMG_20210518_110024.jpg
    IMG_20210518_110024.jpg
    2.5 MB · Views: 163
When you took that fan controller apart you totally damaged it. You have to remove the four T20 bolts behind the label with the part number. Remove the alloy plate and then carefullt take out the stainless blade spring that press the MOSFET transistors and the SCHOTTKY rectifier diod towards the heat pad on the (coolant) alloy casing.

You have now distroyed all transistors and the rectifier diode and most likely the PCB by just pulling the PCB out. :(
Fan controller dismantled and yes obvious signs of water ingress, the seal seemed to in place OK.

Took the car out today with the roof open as the sun was shining, went to my usual parking area to find a fellow A2, no sign of the owner though.
 
Back
Top