Heater issues XJ12. Delanair3 type.
Heater issues XJ12. Delanair3 type.
hi there,
This is my first post here.I have an 88 XJ12 series 3. I have heater issues. I was trying to take the heater valve off, but after dropping the ratchet down the back gave up. I found actually the lever would move with a screwdriver, but there does n't seem to be any vacuum at the flexible. I'm not sure what my next move is.There is hot air coming in on the drivers side vent, (LHD) and cool air on both foot well vents. That doesn't change whatever the heater controls are turned to. It will demist hot too. There's not really cold air air coming in and nothing from the center vents. also no temp change really. fan speed does n't change either.Could be the servo or vacuum system I suspect. I have the passenger side panel off and it looks a scary mass of plugs and wires. I notice in my Haynes manual that there is a fuse for the air con controls and air con fan as I have n't seen the electric fan working. It was working before. It is supposed to start when the system switches to full cold I believe. Hope this is not too many questions in one go! I'm not completely useless as I fixed a lot of things on my own before I got onto this great forum.
Any ideas would be great.
Jonnyjag37
This is my first post here.I have an 88 XJ12 series 3. I have heater issues. I was trying to take the heater valve off, but after dropping the ratchet down the back gave up. I found actually the lever would move with a screwdriver, but there does n't seem to be any vacuum at the flexible. I'm not sure what my next move is.There is hot air coming in on the drivers side vent, (LHD) and cool air on both foot well vents. That doesn't change whatever the heater controls are turned to. It will demist hot too. There's not really cold air air coming in and nothing from the center vents. also no temp change really. fan speed does n't change either.Could be the servo or vacuum system I suspect. I have the passenger side panel off and it looks a scary mass of plugs and wires. I notice in my Haynes manual that there is a fuse for the air con controls and air con fan as I have n't seen the electric fan working. It was working before. It is supposed to start when the system switches to full cold I believe. Hope this is not too many questions in one go! I'm not completely useless as I fixed a lot of things on my own before I got onto this great forum.
Any ideas would be great.
Jonnyjag37
Veteran Member
Joined: Mar 2008
Posts: 25,520
Likes: 11,712
From: Pacific Northwest USA
hi there,
This is my first post here.I have an 88 XJ12 series 3. I have heater issues. I was trying to take the heater valve off, but after dropping the ratchet down the back gave up. I found actually the lever would move with a screwdriver, but there does n't seem to be any vacuum at the flexible.
This is my first post here.I have an 88 XJ12 series 3. I have heater issues. I was trying to take the heater valve off, but after dropping the ratchet down the back gave up. I found actually the lever would move with a screwdriver, but there does n't seem to be any vacuum at the flexible.
Vacuum is applied to CLOSE the valve when max cooling is called for. For heating, or blending hot/cold, vacuum is turned off to open the valve.
So, if you're asking for heat there should be no vacuum
I'm not sure what my next move is.There is hot air coming in on the drivers side vent, (LHD) and cool air on both foot well vents. That doesn't change whatever the heater controls are turned to. It will demist hot too.
If you're getting hot air anywhere then the heater valve is working as it should. The fact that the hot air isn't going where it should go suggestes the the servo motors are not operating
There's not really cold air air coming in and nothing from the center vents.
The center dashboard vent operates only when max cooling is called for.
also no temp change really. fan speed does n't change either
Could be the servo or vacuum system I suspect.
Could be the servo or vacuum system I suspect.
Several possibilities.
Temp (and outlet flow) is changed by flaps operated by servo motors and a couple of vacuum actuators. The servos and/or actuator could be dead or perhaps they are not being commanded to operate
Spending a couple hours cleaning the connectors and grounds *might* be all that's needed. Scroll down a bit and read the "A/C Won't Shut Down" thread. Not exactly the same problem but there's some good reading there
I have the passenger side panel off and it looks a scary mass of plugs and wires. I notice in my Haynes manual that there is a fuse for the air con controls and air con fan as I have n't seen the electric fan working. It was working before. It is supposed to start when the system switches to full cold I believe.
Checking/cleaning/replacing fuses is a good place to start.
What Haynes book are you using? Does it cover the MkIII system? I'm betting it doesn't but make sure either way to avoid lots of confusion.
If cooling is asked for the fans (plural) should start right away. If heating is called for then the fans won't turn on until the engine temp reaches 150ºF or so
Cheers
DD
Thread
Thread Starter
Forum
Replies
Last Post
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)