VW Golf Mk2 Owners Club

heater matrix bypass

September 04, 2023, 11:07:26 AM

Hi.  There is no heat coming from my sons heater in his mk2 Golf driver.  I've checked the hoses to the matrix and they are cold, so I'm assuming the bypass device is seized.  I know I could just remove it, but the car is on its original matrix.  Its a very late 1991 model.  Has anyone tried to repair one of these?  I'm assuming the aluminium take off point is what clogs up inside.  I've no idea how it works.  Does it have a diaphram inside like the main thermostat?
Thanks

Re: heater matrix bypass

Reply #1 – September 06, 2023, 10:55:22 AM

Hi,

If you still have the bypass valve, your best bet is to remove the valves completely for a piece of metal tubing.
If you're certain you still have the original heater matrix, you may as well swap it out for a new one, they're pretty cheap, though a little bit of a pain to swap out. There is a guide somewhere on here to do the swap.

Re: heater matrix bypass

Reply #2 – September 06, 2023, 01:05:51 PM

100% change the matrix.
I would expect the foam covering on the airflow direction flaps has all disintegrated by now anyway and will need replacing. So even if you get hot water to the matrix you'll never get heat into the car as you won't be able to close off the cold air from outside.

It sounds daunting, but it really is quite easy to remove the dash. Many people do the heaterbox removal with the dash in place but my personal experience it that its really not worth the effort and hardship.

With the dash out you can also check, and repair if needed the windscreen vents as the dash tends to delaminate and separate here.
It's also a good chance to change the dash speakers and it gets you a good view of the bulkhead, especially below the windscreen to check for rust and rot.

With a new matrix, get a decent branded one and you'll be fine. You can then remove the bypass and fit new hoses which are available fror B&B components (tierod69) on eBay among other places.

Re: heater matrix bypass

Reply #3 – September 06, 2023, 09:17:51 PM

Agreed Tim.
I'd shake the dash too to get rid of any bits of sponge that are in the dash void. You may need to reinforce the dash aperture which fits over the heaterbox since it can get mis-shapen. Best do all you can whilst the dash is out.
Disintegrated foam on the heaterbox vents can be a sticky mess to sort. But pre autumn is the best time to do it.

Re: heater matrix bypass

Reply #4 – September 07, 2023, 02:04:06 PM

Thanks everyone.  I've ordered a new matrix and hoses.  I've looked at the various youtube videos and it doesn't look to difficult to pull the unit out.  I've already had the lower dash out to seal up the holes in the heater flaps, and taking the whole unit out doesn't involve that many extra steps.