mk4 heater control valve???

[Andy52]

Hi can anyone shed some light on how this works, and what exactly is it supposed to do.

I have had no heater since xmas as i thought the matrix was leaking into the cabin. But have now found this not to be the case. So today i re-connected the pipes back to the heater control valve. I did however, before connecting all the pipes, connect the valve up and turn on the ignition and the heater. But the valve did not turn or click. Heat is circulating from the engine through the heater and there is no leaks. So i was wondering what is the valve supposed to do.??? 

[Cragrat]

Had this a few years ago on a 51 plate 1.25.  Found it was a bad earth.

[rustyroger]

It seems the heater control valves are a noted troublespot. I learned the hard way that cheap replacements from eBay and other websites are not much good. However my local motor factor supplied me with a good one for about £25 if memory serves. It's still working fine.

 

Roger.

[MJNewton]

The valve is a solenoid that switches between letting hot water through the heater matrix or not. On max temp setting the valve remains constantly open, on min temp setting constantly closed. For any setting in between the valve is operated on a pulse width control with a varying proportion between open and closed depending on the set temperature. With it being a mechanical part in near-constant use it is very prone to failure. Most cars have a simple flap that just adjusts the proportion of air passing through the heater matrix - really simple and really reliable. Ford have made an absolute killing in replacement valve costs though so who can blame them?

With the temp control set to a middle setting you should hear/feel the valve opening and closing of 1-2 seconds or so. If it isn't then either the valve or control board has failed (I'd suspect the former in the first instance).

[Andy52]

hi thanks for the info about this. I will check it out in the morning, have noticed that the heater gets really hot then it goes luke warm . It is now running quite cold. What would happen if i bypassed it completely. ?? 

[MJNewton]

When the solenoid is fully closed there is an internal bypass loop that keeps the flow going so bypassing it (i.e. connecting one pipe to the other) would just have the same effect (and it'd run cold). I did exactly that, using a short length of 15mm copper pipe and a couple of jubilee clips, one summer as I would've been cooked alive otherwise!

[Andy52]

So if I put the pipes direct to the heater matrix rather than going through the control valve would only make it hot inside the car then. That would be a bonus at the moment.

[MJNewton]

It would indeed.

(Apologies; I should've suggested that straight away given the time of year - I couldn't shake off the nightmare summer days being roasted!)

[Goochy81]

Andy52 sorry to hijack your post mate but it seems we are in the same boat (cold fiesta). Ive got a mk4 im trying to restore. The heater isnt blowing hot air into interior. Ive replaced thermostat. Renewed coolant. Bled system. Hot pipes going into hcv and coming out into the matrix. Also hot pipes coming out of matrix back into hcv. Heater blower working. Im at a total loss. Any ideas? Mjnewton you seem knowledgable. Any ideas? P.s im a amateur mechanic using a haynes manual but exhausted all their pages on the topic lol

[Andy52]

Hi Goochy81, It sounds like a popular problem on the mk4. Although my previous mk4 had a brilliant heater. When I got this one, the heater wasn't working, it was suggested that it could be the hcv, I changed it for the one off my old car, as I knew that worked, and I had a heater for about 3 months. Then I noticed it wasn't getting as hot as normal, and my footwell was getting wet. So I assumed matrix had split, and bypassed the whole heater. Carpet dried out, but its been a cold Xmas. Flushed heater matrix and no wet carpets. Reconnected the heater through the hcv, and its been very intermittent with heat. Some have said hcv, and some have said that the controls themselves could be at fault. That's my next step before bypassing hcv. Your problem seems more heater controls. Have you checked to see if the controls on the dash are operating the heater properly. It heat is going in, and coming out, then unless the heater is stuck in a cold setting, you should have heat. 

If I can't find a problem changing the controls, I'm going back to basics and going to run heater pipes from engine to matrix to engine, and forget the hcv. 

Good luck with your restoration, sorry can't be more help. 

Andy52.

[Goochy81]

Thanks Andy. Really appretiate the help. I think its a problem with the electric control on the dash. Yesterday afternoon. Ive had the heater matrix out. Flushed it no problem. Its not leaking too. Hcv is letting hot water through and letting it return back through via the matrix. Im thinking the control dial has packed up. Thought it might be cable operated but its an electrical unit. Trying to hunt for one of them now but they seen rarer than rocking horse s....t.

[MJNewton]

I think I might have a control panel available - will check this evening. It might be a different colour to yours given the varying trim levels but you might be able to just swap the PCB over. 

[Goochy81]

That would be great if you have one. Thanks for that mate.

 

[MJNewton]

Just had a look but couldn't find it - I suspect I chucked it when we sold our Mk 4. Annoying that as I don't like throwing anything away in case it might come in useful one day!

You said they seem rare but there are loads on eBay at the moment?

[Goochy81]

No worries. Thank you for looking. eBay it is then lol 

[Andy52]

Well i checked controls, and it is definately the hcv. So i will be investing in a new one at some point. Heater pipes now run straight to heater, so once engine is at running temp, we are toasty inside. 

Next job is changing front wishbones. Here's hoping for some dry days, as i don't have a garage. .Wish me luck....