Fan Control Module (FCM) Blowing the 20A fuse constantly

[ABV-VR6 12]

Maybe one of you would have an idea of what does that? 

There's 2 fuses on the FCM,  a 5A for the auxiliary pump and a 20A for the cooling fan. The 20A always burns out, like every drives. Everything is new... The cooling system works flawlessly other than that. 

What comes to mind is it's either the new Meyle FCM (couldn't find an OEM one) that is faulty? I'm running two electric Spal fans wired properly to the OEM harness just like Charles the humble mechanic did on his VR6. 

I'm not sure what to think of it, any idea? Cheers 

[Cressa 44]

Are you able to test and make the fans run? Not by driving, but by linking out the sensors to make them come on. Maybe have the car on a charger too so that you have a good voltage and can spend a long time looking

If a fuse blows straight away, it is an incorrect connection somewhere shorting it out.

If a fuse blows after a while of usage the circuit is drawing too much current.

If the wiring is of a larger size, you could try a 25A fuse say, as long as it is below the current carrying capacity of the cable

Your fixing bolts to the controller do look good 👍 

Good luck with solving this problem. 

[ABV-VR6 12]

7 hours ago, Cressa said:

Are you able to test and make the fans run? Not by driving, but by linking out the sensors to make them come on. Maybe have the car on a charger too so that you have a good voltage and can spend a long time looking

If a fuse blows straight away, it is an incorrect connection somewhere shorting it out.

If a fuse blows after a while of usage the circuit is drawing too much current.

If the wiring is of a larger size, you could try a 25A fuse say, as long as it is below the current carrying capacity of the cable

Your fixing bolts to the controller do look good 👍 

Good luck with solving this problem. 

Thank you Cressa, all good points! 

I'm going to head out to the garage and jump the sensor first like you said. Won't take long to check that out. 

The problem happens after a while, not instantly. 

I might reinstall the old but factory FCM to see if I get the same problem. I've read there's been a recall a long time ago with FCM. Original one had 3 speeds for the A/C and upgraded version operated differently. Make me wonder if the A/C delete as something to do with this. 

One step at the time and hopefully I can figure it out! Cheers 

[ABV-VR6 12]

Ok well a little update. So like you said, I started with the basics and I jumped speed one, the one fan came one like it should. But when I bridge for speed 2, I got nothing... I opened the loom to find out something that I've done and forgot the mental note and a year went in between. Anyways, in my process of deleting the factory installed AC, I had made the call to not wire up the third speed since the car would not have AC anyway. I had forgotten this and the loom was ready to go if I wanted to install that wire again, so I did. I'm not 100% sure it will make a difference for the 20A fuse that blows every trips but now I have speed 2 that works... So that's progress. I'll have to wait for a sunny day and test drive it to see what happens with the fuse. 

I'll report back. Thanks for your guidance, I was so sure everything was done by the book and by going back doing those tests, I found out that I'm loosing my memory ha haa. 

[Cressa 44]

Well done in hopefully sorting it. Sometimes it is hard to go back to the beginning to check things as we are 200% confident they were done right. Always catches me out and I end up back at the beginning 2 weeks later.

We can always send you a non AC FCM unit across the water if you need it 👍

[ABV-VR6 12]

Well thanks to you because I was so sure and that incited me to go back. Ya, I was 200% sure... Done so much that I forgot things... The FCM I purchased is a 506. What's the part number for the ones you guys uses? 

Cheers mate 

[tonedef 9]

Mine’s. 506 too, only number I can read on the photo I’ve got as I’m away from home at the moment. I bought it without a/c but have since fitted Climatronic from a Passat which uses the FCM, I had to add extra pins to the plug for the additional signals.

I seem to remember somebody posting here years ago that all the run out cars came with the same FCM a/c or not.

[ABV-VR6 12]

Thanks mate for jumping in the discussion. I originally bought a FCM that was made for non AC cars but there's no after run pump fuse to it and only one plug. I wonder if it is the UK cars without AC got? 

[tonedef 9]

From the VIN number, mine was produced 342 from the end of the production run so they were probably using up the parts they had left, and I’ve owned it since it was less than five years old so I expect it’s the original one too as it was too new for things to have started breaking! No UK cars were built with a/c but mine is definitely 2 plug and I’m sure that both plugs were wired when I fitted the Climatronic, I just had to add extra wires to the smaller plug.

 

[ABV-VR6 12]

Thank you, so that confirms that the 506 is definitely the right one. Thanks for checking it out! I think the one that was sold to me as a non AC car FCM was from a MK3 VR6. That could be it! At least, now I know for sure that I have the right one. 

The weekend looks sunny, I'll take it for a spin and see if my latest wiring modification made a difference. Cheers 

[ABV-VR6 12]

I've ordered a new FCM on eBay a couple of weeks ago, Hüco brand made in Germany. It was supposed to be a 506 version but they sent me a 506A. They look identical apart from the fact that the 20A fuse is now a 30A and there's no 5A fuse on it. Is this a newer version and they merged both fuses together or it's a totally different one? Anyone tried a 506A before? 

[Cressa 44]

Just checked mine, which is just a 506 same as tonedef. Even my spare is the same.

Both 20A

[ABV-VR6 12]

Thanks mate. 

I wonder if there's a difference between 357 and 3A0 then? 

At this point, I don't think 506A will work, probably more for 95+ MK3 with obd2 maybe? 

I finally went for a drive yesterday, nothing as changed, I left with a new fuse and came back burned. 

 

[tonedef 9]

From a set of Passat wiring drawings I used when fitting my Climatronic, the terminals associated with the 4 pin plug on the FCM are:

T4/4 12V Feed from battery

T4/3 Signal from F18 the radiator thermo switch

T4/2 Fan speed 2

T4/1 Fan speed 3

The fuses are:

S78 5A fuse for the coolant pump

S108 20A fuse for fan stage 1 and a/c magnetic coupling (although to me it appears that stage 1 is fed directly from the thermo switch which may then suggest this fuse is stage 2….hypothesis only!).

S107 50A fuse for fan stage 2 & 3

So if the 20A fuse keeps blowing, is there a chance you have a short to ground on the  a/c magnetic coupling wiring from when you removed it? The magnetic clutch feed is on the 10 pin plug T10/10…or it is on mine which replicates the Passat at least. Or is the short on one of the fan stages, 1 or 2 dependent upon which stage fuse S108 feeds.

[ABV-VR6 12]

You are bringing a very good point and I can't thank you enough for taking the time to help me out with this. Because honestly, I know some stuff but this got me totally baffled. 

So, ya I'm incline to think it's AC delete related. Maybe I'll have to go back to my "how to" file and double check everything... Make sure everything is completely isolated. From there, I'll see if there's any changes. Weekend project! The rad thermo switch is new and oem btw. 

Thank you kindly! Cheers 

[fendervg 32]

The AC cars would have had a different fan control module installed, with an extra stage, and there would be additional wiring. There is also a different third temperature sensor in the thermostat housing for AC cars - I forget the colour, but it would be 4 pin.

[Dox 23]

If this was me I’d unplug the fans, replace the fuse and test drive. If the fuse remains intact it’s something to do with current draw of the fans themselves.

if the fuse burns, you have a wiring issue (the power consumers were disconnected).

[tonedef 9]

4 hours ago, fendervg said:

The AC cars would have had a different fan control module installed, with an extra stage, and there would be additional wiring. There is also a different third temperature sensor in the thermostat housing for AC cars - I forget the colour, but it would be 4 pin.

I  agree there’s a different 4 pin sensor in the stat housing as I remember having to source one, although I don’t remember the colour either. The FCM didn’t need changing when I installed the Climatronic, although I did have to add a few wires and pins to the ten pin plug that weren’t on the Corrado loom. Since then I’ve installed another loom when I converted to OBD2 from a Golf  but it went straight on the same FCM.

I’m sure I remember that the later cars had a different controller installed which is how I expect mine came with this one, it definitely worked fine without the additional a/c hardware and the car was less than five years old when I bought it so I doubt anything had been messed with by then.

[fendervg 32]

Only seems to show two different versions for the ABV engined cars  - with air con or without

[ABV-VR6 12]

On 10/4/2023 at 7:05 AM, fendervg said:

Only seems to show two different versions for the ABV engined cars  - with air con or without

 

On 10/4/2023 at 12:04 AM, fendervg said:

The AC cars would have had a different fan control module installed, with an extra stage, and there would be additional wiring. There is also a different third temperature sensor in the thermostat housing for AC cars - I forget the colour, but it would be 4 pin.

That's correct, it's brown or black. When I deleted the AC system I left that one unplugged. After checking my wiring again following Cressa's advice and found my third speed wire not connected to the fan, I plugged this sensor after the work. Maybe that's something else I could check, unplug the sensor and see if it changes anything... 

[ABV-VR6 12]

On 10/4/2023 at 12:13 AM, Dox said:

If this was me I’d unplug the fans, replace the fuse and test drive. If the fuse remains intact it’s something to do with current draw of the fans themselves.

if the fuse burns, you have a wiring issue (the power consumers were disconnected).

That is such a good call! Very good idea and simple logic that makes total sense. It's colder on evenings now, I could go for a short drive and test that out. Thank you! 

[ABV-VR6 12]

On 10/4/2023 at 5:07 AM, tonedef said:

I  agree there’s a different 4 pin sensor in the stat housing as I remember having to source one, although I don’t remember the colour either. The FCM didn’t need changing when I installed the Climatronic, although I did have to add a few wires and pins to the ten pin plug that weren’t on the Corrado loom. Since then I’ve installed another loom when I converted to OBD2 from a Golf  but it went straight on the same FCM.

I’m sure I remember that the later cars had a different controller installed which is how I expect mine came with this one, it definitely worked fine without the additional a/c hardware and the car was less than five years old when I bought it so I doubt anything had been messed with by then.

My car is one of the last as well, SK001010. So technically the 506 is definitely what I need and that's what is installed. 

[ABV-VR6 12]

5 minutes ago, ABV-VR6 said:

 

That's correct, it's brown or black. When I deleted the AC system I left that one unplugged. After checking my wiring again following Cressa's advice and found my third speed wire not connected to the fan, I plugged this sensor after the work. Maybe that's something else I could check, unplug the sensor and see if it changes anything... 

It's actually the brown one on the right formerly yellow colored. 

[ABV-VR6 12]

On 10/4/2023 at 7:05 AM, fendervg said:

Only seems to show two different versions for the ABV engined cars  - with air con or without

The interesting part is that it shows the replacement for it being 506A which is what I received when I ordered a 506. 506A as the one 30A fuse, not the 20+5 on the 506 

[fendervg 32]

I think it is meant to be read as the 506 being the replacement for the 506A. It's a bit of a minefield really - is it worth doing a poll of other late cars that had AC installed to see what they have? The E certainly just seems to be for other engine types. 

The other thing to bear in mind is that no UK cars had factory air conditioning installed, they were always a dealer retrofit - so did they replace the fan conrol unit with the correct one, or simply use the existing standard VR6 one and maybe change the wiring? Hard to know.