Heater matrix size of connections

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pointer
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Passat model: 1741 estate 1991

Heater matrix size of connections

Post by pointer » Wed Nov 20, 2019 5:22 pm

Does any one know the internal size of hose connections to the heater matrix as I am contemplating a flush due to no heat in the car?

gtijames
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Re: Heater matrix size of connections

Post by gtijames » Wed Nov 20, 2019 8:10 pm

Are both hoses nice and warm when the cars up to temp? If its sludge in the matrix in my experience no amount of flushing will budge it and its dash out with new matrix time!
I've tried with a hose pipe down the pipes of the matrix before it's almost the right size

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fonzooorooo
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Re: Heater matrix size of connections

Post by fonzooorooo » Thu Nov 21, 2019 3:18 pm

^exactly this!

I'm sure you've heard of the evil foam covered doors in the heat distribution box... 1 of them regulates hot/cold on these cars (the matrix remains hot regardless of heat position) so your issue could be there. ... Personally, if I need to do a matrix, I do the foam on the doors at the same time (or vice versa) so it's only 1 strip down instead of 2.
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pointer
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Re: Heater matrix size of connections

Post by pointer » Fri Nov 22, 2019 10:48 am

Not sure what you mean about foam covered doors or heat distribution box. I will try the flush through first anyway as the return from the matrix is cooler than the flow. Let's hope it is just that :-?

maclee
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Re: Heater matrix size of connections

Post by maclee » Fri Nov 22, 2019 4:33 pm

Here is the parts illustration for a 91 Passat air distribution system.

The 'heat distribution box', (VW term, 'Air Distribution Housing') is item 1 (circled).

It has doors at each of its outlets that open or close to allow or prevent the flow of air to certain areas, such as the windscreen, dashboard or footwells. These doors are fitted with seals made of foam. The foam can degrade over time and become sticky, holding the doors in place, or, more likely can disintegrate and impinge on the movement of the doors.

Item 2 is the matrix.

Please bear in mind that, like most VW diagrams, this one is for LHD cars. The RHD arrangement is practically a mirror image, but many of the parts are different as a result.


91passatair.png
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maclee
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Re: Heater matrix size of connections

Post by maclee » Fri Nov 22, 2019 4:59 pm

Just re-read this thread.

Have you checked the operation of the hot/cold knob on the heater panel?

This is an evil mechanism that relies on vertical gears on the back of the knobs turning horizontal gears which have channels or cams formed in them. In the channels run pins that are mounted on levers. The position of the pin in the channel dictates the position of the end of its lever. These levers pulls on cables that are attached to the doors in the air distribution housing.

The outer of these cable are clamped in place to the heater control frame with metal spring clips.

The frame, gears and almost everything else is made of that really brittle plastic that only German manufacturers seem to use, (used to find it all the time in old Grundig and Telefunken TVs).

Often, when the heater control fails to make any difference to the temp, or the air distribution knob makes no difference to where the air escapes, it is down to the plastic gears having broken or lost teeth, or, more usually, to one or more of the cable clamps for the cable outer having broken away from the control frame. When that happens the cable no longer alters the door position, instead the cable just moves itself, not the item to which it is attached.

Here are a couple of photos, (again, I believe this to be the LHD version which cannot be fitted to a RHD car)


a.jpg
b.jpg
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pointer
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Passat model: 1741 estate 1991

Re: Heater matrix size of connections

Post by pointer » Fri Nov 22, 2019 11:40 pm

Thanks Maclee. I had already taken the heater controls out and found the temperature regulator knob was not moving the cable. I removed the gearing (with difficulty) and found that on the reverse side there was a 'concentric' channel for a 'spigot'on the end of the inner cable to move where the spigot was not in that channel.

I refitted every thing including relocating the spigot and operated the control knob in a hope I would have heat but, alas not to be! Consequently my thoughts centered on flushing the matrix.

However, seeing the the last few posts there could be other problems with either the 'doors'/flaps or the securing of the cable it self at the heater control.

Weather permitting, I will try a flush first and if that doesn't improve matters, it looks like in depth dismantling of both the heater controls and/or 'door'/flaps. Oh joy Oh Rapture #-o

maclee
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Re: Heater matrix size of connections

Post by maclee » Sat Nov 23, 2019 1:41 pm

Those heater controls are the work of the devil!

Here is what might be an easier diagnostic you could try, (sorry, my B3 days were too long ago to recall all details):

Trace the path of the hot/cold cable to its lever on the air distribution box.

Disconnect the cable from the lever, (I think it just hooks into a hole), and set the lever to the hot position. (You may be able to do this without disconnecting the cable but I cannot remember for sure).

Alternatively, disconnect the cable at the controls end and move the cable to the hot position, (I really do not recommend you ever disturb the cables at this end though, a the plastic will almost certainly disintegrate and give you another headache of you do).

If you then have hot air from the heater you will know that the matrix is OK and that you have an air-control problem.

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