When i bought my XK i realised that the cupé heat did not work, it was stone cold dead. In the back of my head i was thinking it was that water cirkulation pump for the heater core that had given up. Easy fix.. or?

I bought a used but "checked" pump from a dealer and when replacing the cracked, big plastic piece abbove/behind the engine, i had a go at the pump. Carefully taking a note of where all the hooses go, i removed them all and yanked the heatervalve/pump assembly up and out. Before i installed the "new" pump i opend it and checked the bruhes on the motor, they where half way worn out... good enough for me.. so i put it all back and fitted all hooses again.. a PIA but doable.

No help. No heat in cupé. Stone cold.

Digging in a little deeper to the problem i realised that the hooses that are conneceted to the heater core where quite cold to the touch even after a nice tour on the countryside, meaning the water refuses to circulate. That promted me to suspect two things; 1) the left hoose (water exit) from the heatercore has a very sharp bend before the checkvalve.. too sharp? 2) The heater valve.

-After scouting a parts site for a suiteble hoose to cut a nice bend from, bought it, cut it to fit, and i replaced that flat bend to make sure thre was no unnessesary restrictions of the waterflow.

-When checking the heater valve by supplying 12V directly nothing happend. I was expecting some kind of "klick/klock".. but no, dead. I replaced the heater vavle but did not connect it yet, when not connected the valve are supposed to be "open" and let water through.. witch it did. Before installing the "new" control valve i did check it with a battery and it did do the "klick/klock" satisfactory.
With engine up and running, settings to "hot" the electrical pump did pump water through the heater core, hooses got really hot and so did the cupé.. unbeleivable hot..

The reason i did not connect the heater valve directly, was that i had read that a faulty/shorted heater vavle could burn out the driver cirquit in the "Climate Control Module"... so i just played it safe. Since i got water through the core again i reasoned that i might as well connect the plug to the control vavle.... witch did absolute noting to control the heat.. it was gushing hot air on my feets.. and anywhere it felt like..

Soo ..i bought a second hand climate control module and replaced it and hoped for the best. ...did the in the manual described test, resetted a few residual faultcodes and yeeees! it all started to work as it should.. hot, cold and any configuration worked just fine again. :-)

-The climate control module are in a LH drive XK, installed in the passenger footwell, behind the glovebox towards centerconsole. (se picture) The climate module drive the electrical water circulation pump via a fused relay and the water control valve are driven directly from the module.. witch means that if the watervavle somehow draw to much current, the module might give up i one way or another.. Maybe it can give up anyway due to fatique. (i did ofcourse opend the old module to see if there was anyvisible signs of why it had given up.. but no, nothing..
-I also (ofcourse)took apart the old faulty water control valve and i noticed one important thing; the stroke of the valvething inside, is not more than 5-6 millimeter. The rubber seals had swollen up really bad, making it impossible for the valve to move, completely blocking the water... i.e. no "klick/klock. So, the water vavle can be shot, even though the coil itself may be ok.

In my case, everything involved was broken.. but are now ok again.. :-)



Position of the "Climate Control Module"

 

Well done on resolving it and thanks for sharing 👍