Heater fan speed reduced after slave cylinder and flywheel were replaced?

MRPAULHARRIS

MEMBER
2012 VOLKSWAGEN TRANSPORTER
2.0L
4 CYL
2WD
MANUAL
205,000 MILES

After my concentric slave cylinder failed, I had it replaced as well as flywheel and transmission parts.

The Gears and clutch pedal now work very well, but strangely when I turn on heating inside the van it does not blow very strongly. This change occurred exactly when I picked my van up with the new slave cylinder. It seems at all fan speeds 1 through 4 the air does not blow strongly but when I put it into reverse and pull back on the clutch pedal the fan blows much stronger (at the strength it should be and indeed was before the transmission repair).

I typically back into my driveway and the full fan strength only comes on when I start to release the clutch pedal in reverse. Also, when I stop the van and put it into neutral, the fan speed goes slower again. This only happens in reverse: when I park forwards, the fan strength does not increase.

Also, when I turn the ignition off, there is an electrical humming for about 1-2 minutes that never happened before the transmission repair. I opened up the bonnet and I can hear the humming. It seems to come from the area of the master cylinder and brake fluid area.

Any ideas?

8 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,947 POSTS

Yep, it sounds like they left a ground wire off when the repair was done, I would take it back to them and have them recheck there work. Let me know how it goes.

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Friday, June 23rd, 2023 AT 11:53 AM

MRPAULHARRIS

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17 POSTS

The van was taken back to recheck the work. An auto electrician ran over it and I was told that changes in fan volume is a feature built into the Volkswagen. When reversing it switches to air recycling mode, so that fumes don't get sucked into the vehicle when reversing. And on my vehicle the recycle mode does cause the fans to spin faster.

The electrical humming, I hear after I turn the engine off, was proposed to be the fuel filter doing some final pumping (not sure why). Alternatively, it has been proposed there may be some electrical interference that would require additional investigation.

I am not sure I am completely satisfied by this humming explanation. But as it is not really affecting me, I have left it at that for now.

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Monday, October 2nd, 2023 AT 12:47 PM

KEN L

MASTER CERTIFIED MECHANIC
42,947 POSTS

Did this problem happen before the repair? If so, it will not be related, and we will need you to start a new thread. It still sounds like they left something off like a ground wire or an electrical connector is dirty or not plugged in completely. There is a ground G304 at the base of the right-side door pillar I would check, here is the blower motor wiring diagrams so you can see how the system works, if the ground is okay, we should do a CAN scan. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

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Tuesday, October 3rd, 2023 AT 10:31 AM

MRPAULHARRIS

MEMBER
17 POSTS

I found a disconnected wire (photo attached).

Thanks for the electrical diagrams, I traced them and found my G304 ground near my pillar. The electrical diagram says G304 is "Base of right D Pillar". "D" means the rear pillar. I had attached 2 years ago additional wires to this ground: my house battery, inverter and dcdc charger. These all predate the problem with the fan speed and have all been working flawlessly for me for the past 2 years.

I have been researching which odb2 CAN scanner to buy so I can run some diagnostics for you. I am leaning towards a Bluetooth scanner, hopefully that supports CAN as well as has the ability to turn off the 'service due' indicator.

So how did I find a disconnected wire?

One week ago, I started hearing some rattling sounds whenever I drive. It's happening all the time but erratically. I imagine there is a tool or something loose in the engine, rolling around.

So, I took the bottom plastic shroud off and had a look. To my surprise, I found an electrical socket that looked like it should have something plugged into it. Then I found a cable not plugged in to anything. So, I have plugged them together and they fit well.

I am in disbelief at my mechanic. Even when I took it back to them and explained the problem, how could they miss this? I am pretty annoyed.

Do you know what this cable does?

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