Heater problems with climate control

[aceventura]

I have been reading a few posts regarding this problem, but they all seem to present in slightly different ways. I don't know when mine stopped working, because it has been fairly warm of late. These are the checks I have done:

All other aspects of the climate control work perfectly.

A diagnostic check on the temperature sensors comes back normal.

One of the heater pipes is hot while the other is warm

If I go to the engine bay and disconect the vacuum hose to the heater tap, both heater pipes get hot and I get plenty of heat (so the heater core isn't blocked).

So is this working correctly? If I have vacuum I don't get heat. If I don't have vacuum I do get heat.

This is strange to me: my understanding of the vacuum solenoids is that they must be energized to direct vacuum to the actuator, and when they are not energized there is no vacuum directed to the actuator. This means that when I set the climate control to H, that it is energizing the solenoid and directing vacuum to the heater tap valve, which closes it off - this stops the flow of hot water. This is all backwards - that said I have not found a setting on the climate control that will relax the heater tap valve, only removing the vacuum hose does the trick!

Can anybody shed some light onto normal behaviour of the heater tap (i.e. should vacuum turn it on or off)?

And if the valve operation is normal - what could be causing my heater problems?

Thanks.

[Harvs82]

I have been reading a few posts regarding this problem, but they all seem to present in slightly different ways. I don't know when mine stopped working, because it has been fairly warm of late. These are the checks I have done:

All other aspects of the climate control work perfectly.

A diagnostic check on the temperature sensors comes back normal.

One of the heater pipes is hot while the other is warm

If I go to the engine bay and disconect the vacuum hose to the heater tap, both heater pipes get hot and I get plenty of heat (so the heater core isn't blocked).

So is this working correctly? If I have vacuum I don't get heat. If I don't have vacuum I do get heat.

This is strange to me: my understanding of the vacuum solenoids is that they must be energized to direct vacuum to the actuator, and when they are not energized there is no vacuum directed to the actuator. This means that when I set the climate control to H, that it is energizing the solenoid and directing vacuum to the heater tap valve, which closes it off - this stops the flow of hot water. This is all backwards - that said I have not found a setting on the climate control that will relax the heater tap valve, only removing the vacuum hose does the trick!

Can anybody shed some light onto normal behaviour of the heater tap (i.e. should vacuum turn it on or off)?

And if the valve operation is normal - what could be causing my heater problems?

Thanks.

From memory, both pipes should be piping hot. Also, is the climate unit the correct one, as they are slightly different between VR and VS, as the temp up and temp down buttons are the other way around... this may affect the system in some way. Could the heater tap valve be faulty, or the air mix door also be faulty?

[aceventura]

From memory, both pipes should be piping hot. Also, is the climate unit the correct one, as they are slightly different between VR and VS, as the temp up and temp down buttons are the other way around... this may affect the system in some way. Could the heater tap valve be faulty, or the air mix door also be faulty?

I also believe both pipes should be hot, and this happens when I disconnect the vacuum hose from the heater tap valve. This could mean that the heater tap valve is faulty, but I have no idea what normal operation is - it certainly isn't ceased.

The climate controler is the original, and was working in the not too distant past.

The air mix door could also be faulty, I am not sure how to diagnose that. Would you expect that the air mix door to be faulty if I get hot air when removing the vacuum hose from the heater tap valve? Do you know what coloured vacuum hose runs the air mix door? The Gregory's manual talks about a black and a yellow hose relating to heater operation but I can't tell what is what based on the description in the book.

Thanks for your ideas, and any others.

[moff_man]

there shuld be a vaccume block somewhere (ither under neath the centre consol or near the heater fan) this is what gets switched from memory. i have seen these be foulty in the past and cause all sorts of issues.

[aceventura]

I will check the vacuum solenoids, I have had some problems in the past with them, but they seem to have been working fine lately.

Just to help sort the problem out: The Gregory's lists the following for the air conditioning control vacuum lines:

Red: Demister vent
Blue: Recirculate door
Orange: Floor duct
White: Centre vent
Black: Heater valve vacuum switch
Black: Vacuum source
Yellow: Heater water valve

I only have one black vacuum line (the vacuum source), where is the other one?

What is the difference between the "Heater valve vacuum switch" and the "Heater water valve"?

Which line controls the air mixer door that was mentioned earlier in the thread?

Thanks

[aceventura]

Ok - problem sorted (sort of ), thanks to moff_man who had it right, and everyone else who replied.

I had the vacuum solenoids pulled to pieces cleaning them cause they were leaking some time ago - When I put them back together, I managed to jam the valve (corresponding to the yellow vacuum hose) in the open state so that vacuum was always flowing to the heater tap. I thought I had run the diagnostics on the climate control properly - turns out I am just an idiot. All the sensors were running correctly, but I didn't know what I was looking for during the solenoid test.

Anyway everything is running ok, but the solenoids are leaking vacuum again, so it looks like I will have to fork out for a new one (or one from the wreckers). Cleaning the dust out inside the solenoids helped once before, but the air is switching to the floor vents under acceleration again as bad as ever

So in answer to my earlier questions:

If vacuum is flowing to the heater tap, the valve is closed and no water flows. For those having similar problems, just disconnect the vacuum line to the heater tap to diagnose this problem, if the heater starts working the vacuum solenoids are not working properly.

I think that both the "Heater valve vacuum switch" and the "Heater water valve" are not present in any given car. I think one relates to normal air-con and the other to climate control (but I may be wrong).

The yellow vacuum hose is the important one in this case.

For those that are interested, I checked the water temperature sensor for the climate control to see if it was working properly. It is clamped with a piece of black plastic to the return water pipe from the heater just behind the climate control. If someone needs to test theirs one day, these were my readings (and mine appears to work):

Temp (degrees) | Resistance (kOhms)
----------------------------------------
85 | 0.18
80 | 0.20
75 | 0.24
70 | 0.28
65 | 0.32
60 | 0.38
55 | 0.45
50 | 0.54
45 | 0.64
40 | 0.76
35 | 0.92
30 | 1.10
25 | 1.36

Hope this helps someone.

[VS_Pete_1]

I only just put a new tap in once a week I open it right up and down to keep it operational. They do seize.

[moff_man]

if you are getting air on your feet or screen under acceleration i would be look at the one way valve on the inlet manifold. being an older car now they do fail and it gets anoying.....