I had a module lying around. So I swapped the two. Exact same result. And I know that the other module works

Next step would be to somehow check if the signal is being sent to the valve by the module by checking at the module

My guess is that that signal is being sent and something is happening in the wiring btw the module and the valve

That, I am afraid, I do not know how to check…

 

I cleaned the sensor. And the wiring. Fault still exits. The sensor is likely at fault. I will try to find a good one and see if that changes

But I agree with you, it shouldn’t make a difference at the valve level

 

if you get the signal coming from the unit all good, then you either need to follow the wire to find the fault or splice a new wire.
cut the wire coming out from the control unit, run a new cable and splice it into the connector at the valve. Totally bypassing the old wire.

 

That would have been a good idea but I dug further into the technical guides and it seems that that valve is controlled by another sensor inside the heater core. That sensor should be fine bc it doesn't show a code for it when you do the climate control test Parker7 posted earlier...

 

checking the wiring diagram i cannot see that at all.
it appears as just the ires from the ac module to the valve.
so the valve is telling it what to do.

all those sensors connect into the ac control module and then the ac control module outputs the corresponding signal.
the only wire to the heater valve is from the ac module.


sensors connecting into module can be seen here




so the sensors may well have an effect on what the valve does however they do not talk directly to the valve.
all the talking to the valve is done via the climate control module

so if the module is sending out the signal the fault lies in the wiring to the valve. re running that wire should fix it.
if the module is not sending out the signal (and you say you have tested a known working module so we rule out faulty module)
then the problem may lie with one of the sensors.

so the next step is definitely test if the module is sending the signal and then go from there.
if the

 

The climate control module has a known fault where it burns out two traces on the board inside the module that controls that heater flow valve in the engine compartment that’s on the right hand side right behind the radiator. Climate control model is under the glove box in the right hand side passenger seat foot area. It’s easy to get the module out and open it up and look for the two burnt traces. A repair can be done to it where they put some resettable fuses in there. and you’ll need to replace your heater control valve under the hood because that causes the climate control module to fry. But do a search on climate control module and you’ll be able to find a lot of information on it

 

See page 143 , particularly the wire " break out " sheet in the page before the schematic diagram

See pin CC28 - 2 which is the blue wire at the heater water valve / solinoid connector

If with a somewhat cool cabin run the temp selector numbers up and down

To know if the climate control module is correctly commanding the heater valve you should see a change of state on the blue wire as a DC value around 13 volts to 0

There may be a time delay in the climate control swinging the command / muscle volts , dampening

If the heating system is working correctly as a put together system a hair dryer on the cabin temp sensor will close the heater valve

Note that it takes a ground for the valve to swing open / close

This ground point is LSG19L which is located on page 29 top right corner ( on the firewall ? )

To know if the ambient temp sensor is working at the sensor it should read 1500 to 2000 ohms on the resistance scale with a 9 volt battery powered meter.

 

well...I gave most of today to this problem. And I finally found the solution

I looked up the climate section of the detailed manual I had (see page 100 in the attachment). The heat valve was fine, as I suspected. The resistance was spot on. The ground wire had continuity. The power wire, however, had no continuity between it and pin 52 (page 83 in the attached manual) on the climate control module!

That was the easy part. But for the life of me I could not find plug CC18 as listed in the wiring diagram. It said the access was from the glove box. But there was no blue plug there. After some frustration, I ended up taking apart the entire centre console. Et Viola! There it was right under the storage box (please see attached photo). I guess in Britain, the centre console storage box is also called "glove box"?! A very logical location for it -.-

Anyway, that blue plug was only partially locked in -.-

I clicked it in. Started the engine. Let it warm up to operating temperature. Turned on the AC. Yep cold as ice! Checked for a signal at the heater valve. Yep

A whole host of other functions like defrost, heated side mirrors etc also go through that plug. But I didn't notice their absence bc we have a heat wave these days ...

AND, the ambient temperature sensor also started to work too! I suspect it also had a function going through that blue plug

Other issues that were solved by that plug properly being plugged in were:
-the control panel for the climate control section of the centre console got a lot brighter (I suspect the dimmer function of the interior lights also went through that plug)
-the engine would stall out and die almost every time I would stop at an intersection while the AC was on (I assumed that this was due to a dying CPS but turns out the engine also supplies a crank signal to the climate control module when the AC is on). Side note: the engine dies about 90% less now but it still dies every now and then when stopping, so I can not completely rule out a dying CPS
-overhead console lights and courtesy back interior lights now go out when the car is locked or after a door is closed (after <1 min or so). I suspected some issue relating to the overhead console itself was to blame for the lighting situation

Who knew eh? I hope this helps some poor soul out in the future. And I wish to thank everyone who helped me out with their advice


CC18 blue plug

CC18 plug location

 

yep, you were correct. For a more thorough education on climate control, I attached the detailed service manual with my previous post!

 

I tried to look at page 143 but of the two attachments you posted, I could not see what you were referring to...for posterity's sake: what was it?

The rest of your suggestions were spot on

 

hmmm, interesting, thankfully that didn't come to pass but I will keep that in the back of my mind