heater runs cool

ijiopel · 07-02-16, 07:29 PM

hi guys the heater runs luke warm on my ur quttro gets a bit hotter when sat ticking over. new thermostat thats been checked everything flushed clean good flow threw heater matrix. car holds correct temp and fan cuts in as it should. any ideas? many thanks mark

Mellis46 · 07-02-16, 07:46 PM

The matrix could still be fubar-ed. it only needs to be partially blocked for it not to heat up yet still allow water through. Was the Same on both my B3 90s and my B5 A4 in fact.

Sandro · 07-02-16, 07:59 PM

Sounds like heater matrix

leggy · 07-02-16, 09:41 PM

Had same problem with my 80...
Not sure of set up on UR, but having had the matrix replaced on mine and with it giving out after just 18mths, well I tried :
Thermostat replacement (located inside coolant housing)
Temp sender replacement (blue thing near plugs)
Coolant flush/change
- all to no avail mind!

Then a friend suggested flushing heater matrix independently from coolant system, and viola! Hot heater again.

Looks like you've tried most of those things though, so aliken to previous comments, sounds like your matrix is foo-bared.

Sandro · 07-02-16, 09:59 PM

Quote:

Originally Posted by leggy

Had same problem with my 80...
Not sure of set up on UR, but having had the matrix replaced on mine and with it giving out after just 18mths, well I tried :
Thermostat replacement (located inside coolant housing)
Temp sender replacement (blue thing near plugs)
Coolant flush/change
- all to no avail mind!

Then a friend suggested flushing heater matrix independently from coolant system, and viola! Hot heater again.

Looks like you've tried most of those things though, so aliken to previous comments, sounds like your matrix is foo-bared.

The problem usually is - using tap water mixed with antifreeze instead of deionised water which affects heater matrix first

leggy · 07-02-16, 10:17 PM

Quote:

Originally Posted by Sandro

The problem usually is - using tap water mixed with antifreeze instead of deionised water which affects heater matrix first

Nah, the problem was a performance car garage that didn't know what the heck they were doing when I entrusted them with replacing my boys heater matrix, or rather a rush job which resulted in loads of crap being left in the hoses and after a time the hoses became blocked and the heater only blew cold-warm air....not to mention a scu-iff(sp?) dash, loose shelf on drivers side, and a broken steering-column switch which they made worse when I took it back the next day to complain!

Flying Frank · 07-02-16, 10:16 PM

Quote:

Originally Posted by ijiopel

hi guys the heater runs luke warm on my ur quttro gets a bit hotter when sat ticking over. new thermostat thats been checked everything flushed clean good flow threw heater matrix. car holds correct temp and fan cuts in as it should. any ideas? many thanks mark

No mention of what your water temp gauge is indicating ? If its indicating cool , I'd try another thermostat.

Assuming its normal , how about an air lock in the heater matrix ?

ijiopel · 07-02-16, 10:23 PM

thanks guys confirms what i thought just did/nt want to take heater box out to find i'd missed something obvious. many thanks mark. there was a lot of crap in system when flushed so would guess even tho water flows through theres stiill vanes blocked up

Mellis46 · 07-02-16, 10:31 PM

Good luck with it, if you havent already try back flushing it as well, you never know? If its ever had anything put in it that shouldnt be in there, heaven forfend rad weld etc, it may be beyond it...

jimh · 08-02-16, 01:10 AM

Before you open anything up, have a look at the heater valve under the bonnet.

The heater valve is a black plastic valve with a couple of water hoses attached. It is down the radiator side of the block at the back, near the firewall and has a bike brake type cable going to a lever on it.

What usually happens, is the outer sheath of the cable slides in it's clamp at the valve. Full movement of the heater lever in the cabin then no longer results in full movement at the valve.
Check you get full movement of the valve to its stops when you move the heater lever. If not, unclip, reposition and reclip the cable at the valve until you do. Once you see what you have to do, it's a one minute fix.

07-02-16, 10:23 PM	#8
ijiopel Newbie! Join Date: Aug 2013 Posts: 8	heater thanks guys confirms what i thought just did/nt want to take heater box out to find i'd missed something obvious. many thanks mark. there was a lot of crap in system when flushed so would guess even tho water flows through theres stiill vanes blocked up

07-02-16, 07:46 PM	#2
Mellis46 Aero Advocate Classic Audi Club Member Join Date: Aug 2014 Location: Lancashire Posts: 1,455	The matrix could still be fubar-ed. it only needs to be partially blocked for it not to heat up yet still allow water through. Was the Same on both my B3 90s and my B5 A4 in fact.

07-02-16, 07:59 PM	#3
Sandro Grown up member Join Date: Feb 2011 Location: Chelmsford Posts: 651	Sounds like heater matrix

07-02-16, 09:41 PM	#4
leggy Senior Member Join Date: Nov 2014 Posts: 1,650	Had same problem with my 80... Not sure of set up on UR, but having had the matrix replaced on mine and with it giving out after just 18mths, well I tried : Thermostat replacement (located inside coolant housing) Temp sender replacement (blue thing near plugs) Coolant flush/change - all to no avail mind! Then a friend suggested flushing heater matrix independently from coolant system, and viola! Hot heater again. Looks like you've tried most of those things though, so aliken to previous comments, sounds like your matrix is foo-bared.

07-02-16, 10:31 PM	#9
Mellis46 Aero Advocate Classic Audi Club Member Join Date: Aug 2014 Location: Lancashire Posts: 1,455	Good luck with it, if you havent already try back flushing it as well, you never know? If its ever had anything put in it that shouldnt be in there, heaven forfend rad weld etc, it may be beyond it...

08-02-16, 01:10 AM	#10
jimh Grown up member Classic Audi Club Member Join Date: Dec 2008 Posts: 122	Before you open anything up, have a look at the heater valve under the bonnet. The heater valve is a black plastic valve with a couple of water hoses attached. It is down the radiator side of the block at the back, near the firewall and has a bike brake type cable going to a lever on it. What usually happens, is the outer sheath of the cable slides in it's clamp at the valve. Full movement of the heater lever in the cabin then no longer results in full movement at the valve. Check you get full movement of the valve to its stops when you move the heater lever. If not, unclip, reposition and reclip the cable at the valve until you do. Once you see what you have to do, it's a one minute fix.