UrS6 - Heater Fan Query

**UrS4boy** · 9 May 2015, 17:00

C4 HVAC Fan info

Originally posted by macspring

While I know I should search the forum, this one might be just specific to my car. ... Sorry Dave in advance if your maintenance items posts cover this specific item.

C4 heater fans commonly fail due to squeeky bearings. Some have tried lubricating the bearing (fan is cantilevered from the motor end) :

In your intermittent fan working/not working situation, I would start by investigating the electrical connections to the fan:

1. The connections at the motor end of the fan:

(but it could be internal connections between those pins and the motor brushes)

Thanks to ECS Tuning for those two photos.

2. Checking the connections at the 4D0820521A fan control module/unit:

Its the gismo with the three wires going into it:

In my case I had weirdness because somebody hacked (and I mean HACKED) day-time running lights on my UrS4 V8 avant before I got it by tapping into the switched power on the HVAC fan control module. Made the fan run weirdly until I killed that hack.

At the worst, you will have to replace the fan, PN 4A0959101A. You could follow the basics of Fred Munro's HVAC fan replacement DIY:

http://12v.org/urs/HVACblowerRR.pdf

BUT because your UrS6 has an additional fan flap controlled by this "Mystery box"
(actually a flap control motor - which the UrS4 does NOT have)

you will need to read my C4 heater core replacement post first (based on replacing the heater core in my 98 C4 avant - since sold):

http://12v.org/urs/C4UrSHeaterCoreRe...ntDIY_Rev1.pdf

There is various pricing for the 4A0959101A HVAC blower fan, depending on quality, as noted here:

http://www.ecstuning.com/Search/SiteSearch/4A0959101A/

Good luck

**macspring** · 9 November 2015, 01:20

Had a quick look at this again today.

Does anyone know how I can tap into the power connection of the heater blower fan 'in' the engine bay to allow me to attempt to trigger the fan to operate.

This will allow me to determine if the fan is definitely working or not. I want to know if it is working or not before having to take it out seeing that it is quite involved.

There is a two pin white connector with a green / white wire and a blue / black wire that looks like it connects directly into the fan motor.

Where do I connect the positive and negative wires to ?

Thanks for any help, as with the weather now I need to fix the fan first and also then subsequently re-do the non working heat flap servos.

**UrS4boy** · 9 November 2015, 01:41

From one of my previous posts in this thread:

At worst it will try to run backwards if you get (+) and (-) backwards.

**mcandmar** · 9 November 2015, 03:19

Climate control not working properly, now there is a surprise

As for the motor test, it would be easier to grab a multi meter and see if there is power at the fan connector.

**macspring** · 24 January 2016, 23:49

Update, was all set to do battle to take out the heater fan.

One step at a time, so disconnected the fan's electrical power connector block, tested same with a mutli meter and the loom had 12v power in it to give to the fan's motor and was about to set up two wires and a battery, when I noticed that one of the male spades on the fan motor was 'pushed' back in it's housing meaning that only one of the two power connectors male spades was mating when the loom's connector block was pushed home.

So rigged up two wires with female connectors to run from the fan's two male electrical spades, making sure the female connector engaged fully with the 'loose' male spade connector, and then at the other ends of the two respective wires, two male connectors to mate to the original connector block on the loom, and the fan works as it should.

Hope this is clear, much simpler in practice than how I seem to have described it.

See Dave's photo of the two electrical connectors on the 'top' of the fan in post # 4.

Haven't heard of this fault before, so may be worth checking for this fault if your fan stops working all of a sudden. Mine must have happened when I took of the fan's two wire connector before when checking 'stuff' for the no heat fault.

The fan motor on this car has to be original, and so this fault has happened to an oem fan rather than a cheap spurious fan.

Anyway fan now works lovely, but still no heat.

So I think the heat fault is one of the following three items.

1. Heater Valve - 983819809 - Is there a way to test this to see if I need a new one or not, without having to swop them between cars ?

2. Solenoid Valve 437906283A - Similarly, is there a way of testing these easily ? I have spares I can swop in from other cars, but an easy test would be handier ?

3. Bleeding the Heater Matrix, I don't think it is this as I've 'used' both bleed screws in the HVAC area under the bonnet to bleed any possible air pockets. Don't believe the matrix is blocked either. Just reapplied I need to feel the heat of the in and the out hose when the car is warmed up.

Still not sure how to test stuff using the heater controls. Can put it into engineer mode easy enough, but do not know what some of the codes mean that I have 'found'.

Any comments, or experiences to cure the no heat issue would be appreciated.

Half way there - now have a fan, just need heat.

**UrS4boy** · 25 January 2016, 02:09

Maybe your no heat problem is the things you are thinking. But maybe not.

Set the heater to 24C and after the engine is warmed up, check whether there is hot water in both the feed and return hoses at the end of the heater matrix.

Both these hoses need to be hot(ish). You can probably test the heater valve with a Miti-vac sucking on the vacuum hose nipple on the valve - assuming the valve is in the closed position when you lift off the rain tray.

If it isn't a valve issue, then it might be the heater flap (BTDT) that allows air to be blown through the heater matrix. Heater matrix might be hot but without air going through it, the cabin will not be warmed up.

DIY pdf: http://12v.org/urs/FredMsTempFlapMotorR&R.pdf

**igor136** · 25 January 2016, 07:42

You need new brushes, thats all

**macspring** · 4 February 2016, 20:36

Originally posted by UrS4boy

Tested this heater valve with my new Mityvac - ( It's a great bit of kit btw, well with the money / getting one). You suck on on the valve and it opens the 'shutter' to let the water flow through the valve. After a say 10 minutes the valve has shut again. When the valve is installed as designed in the car, am I correct to think the solenoid allows a constant vacuum to 'flow' to this valve, so the closure of the valve after 10 minutes whilst just sitting there on the Mityvac is irrelevant ?

and that what's important is that the diaphragm opens the value every time when the vacuum is applied to the valve ???

Anyway as part of the testing to determine why the car's heating doesn't work, mcandmar used his vagc*m to check for stored faults in the heating blocks, there was none and all the valves and solenoids appeared to cycle through their respective functions correctly.

On disconnecting engine's coolant pipes, it now appears that there is no flow in and out of the heater matrix. Unfortunalty for me, what now appears to be the cause of there being no heating is that the heater matrix itself is blocked.

I think I recall in the dim and distant past when it wasn't relavent to me then but it is now, is that it might be possible to clean the coolant system using dishwasher powder added to the coolant for a few days driving. Does this just clean the rust out of the pipes and block etc. assuming it does clean the rust, but would it also unblock a blocked matrix ?

In summary, is there any way of unblocking the C4 heater matrix without having to take it out and replace it. The monetary cost of the matrix is not the overriding issue, the hassle of taking it out of the car is the bigger issue.

Thanks for any assistance.

**UrS4boy** · 4 February 2016, 20:55

It should be possible to confirm a blocked heater matrix by attempting to flow water through it via garden hose connection, T'd into the feed or return lines with the opposite line disconnected. They also sell coolant sytem flushing liquids that are made for automotive applications.

http://www.peakauto.com/products/antifreeze-coolants/flush-and-fill-accessories/flush-fill-kit/

**macspring** · 5 February 2016, 00:35

Used the garden hose, so I know the heater matrix is blocked.

Need some acid based radiator flush to dissolve the blockage ?

Thanks.

**mcandmar** · 5 February 2016, 02:36

Just an after thought, did you try disconnecting the water hose from the valve? We verified the diaphragm is working, but the valve part could be stuck internally.

**UrS4boy** · 5 February 2016, 04:07

Originally posted by mcandmar

Just an after thought, did you try disconnecting the water hose from the valve? We verified the diaphragm is working, but the valve part could be stuck internally.

If possilble, the best way to eliminate the heater valve as an issue would be to remove it before the matrix flushing.

**diesel des** · 5 February 2016, 06:58

Also be careful with the garden hose. I have 7 bar water pressure from the mains here which would burst a matrix. Kill or cure I suppose?

Sent from my LG-H955 using Tapatalk

**macspring** · 5 February 2016, 18:30

Originally posted by mcandmar

Just an after thought, did you try disconnecting the water hose from the valve? We verified the diaphragm is working, but the valve part could be stuck internally.

Sorry, didn't type that I took the valve, pictured earlier in thread, out of the 'circuit' and tested the valve off the car in the garage with the Mityvac. While doing this I temporarily joined the resultant break in the circuit with the hose pipe. Left the coolant circuit empty, and today bought some radiator flush, so going to use two containers of the stuff 'to be sure to be sure', and leave it in longer than the instructions direct, and see how I get on. As Des says 'kill or cure'. But agreed re the mains water pressure, not the ideal way 'forward' to burst it in situ..

Will post results in due course.

Thanks lads for for sticking with this thread, if it comes to it, I know I'll have to take out the complete heater box out of the 'water box' access the matrix to replace, but naturally want to exhaust all options to cure the blockage with the matrix in place if I can.

If it does have to come out, going to 'enjoy' cutting it open to see what went wrong.

Going to order an oem matrix anyway as I never want to have to re-vist this issue again. If it not used, I have one before it goes nla.

My motivation is I really want a heater - when you have one you don't always fully appreciate it.

This is the fourth S car I had with heater issues.

Any further comments or assitance would still be appreciated, as it is not cured until it is cured.

UrS6 - Heater Fan Query

UrS6 - Heater Fan Query

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