heater doesnt work

[greenie60]

I have no heating in my 1987 Daimler xj40. looks complicated and hassle so apart from the obvious fuses/relays where do I start ?
fan works but must admit the controls baffle me

[Orkney]

Simple things first:
Assuming it’s the AJ6 engine and also assuming it’s the same set up as in the XJ-S I had, then there is a vacuum operated heater valve at the rear end of the engine, slightly offset from centre, nearer to the passengers side. These are known to stick after being shut for a while. It’s a plated steel unit with two heater pipes and a much thinner rubber vacuum pipe on the top. Try removing the vac pipe and with a length of plastic tube suck to check that the valve moves. You should see it at least move a little. You can also move it manually to open it to give you heat and it may carry on working after that but it probably would benefit from a new one eventually.

Let us know the outcome,
Ian

[greenie60]

cheers for that i'll give it a go

[naki]

Get the engine hot, remove the passenger knee bolster and feel the heater pipes go see if hot water is entering the heater matrix.
If it is, then you have a control problem. Which will likely be either the control panel, climate ECU, or stuck blend flaps.
You can remove the lower blend motors on the RH side of the HVAC box, and manually turn the belend flaps, using a flat head screw driver. This should unstick them.

[greenie60]

thanks for all the suggestions could be a week or so before I can get started on it.
because my car has only done 33k it makes sense that something could be stuck as its used so little

[naki]

Regardless of mileage, the heating systems can cause issues.
Its the process of elimination to check everything and get them working again. Its not long before the very cold weather could be here?

[greenie60]

Simple things first:
Assuming it’s the AJ6 engine and also assuming it’s the same set up as in the XJ-S I had, then there is a vacuum operated heater valve at the rear end of the engine, slightly offset from centre, nearer to the passengers side. These are known to stick after being shut for a while. It’s a plated steel unit with two heater pipes and a much thinner rubber vacuum pipe on the top. Try removing the vac pipe and with a length of plastic tube suck to check that the valve moves. You should see it at least move a little. You can also move it manually to open it to give you heat and it may carry on working after that but it probably would benefit from a new one eventually.

Let us know the outcome,
Ian

i sucked on the vacuum pipe as you suggested and it moved with a clonk a bit maybe 1/4". not sure if that would be enough also i moved it by hand and it didnt swivel i dont think. maybe you're right and i should just by a new one.
thanks

[Orkney]

Hi greenie,
Does the valve look all rusty and crud covered? Is one of the two water pipes going to that valve hotter than the other. If that’s the case, then the valve is closed. You should be able to move it to the open position with the engine running and the heater control set to hot. It might take a bit of effort to send it to the fully open position. As I say it might start behaving after that but the writing might be on the wall! If that doesn’t give heat then you are left with checking slightly more inaccessible stuff as others have said. Let us know the outcome,

Happy New Year to one and all,
Ian

[greenie60]

I got the heater vacuum valve just behind the engine l/h side to move fully by hand but not as smoothly as I would have liked or expected.
next stage as naki suggested was to check for hot water entering the heater matrix and there was so I will look at the blend flaps next.
I think it will be a controller type problem plus a new vacuum valve wouldn't go a miss.
i'll keep everyone informed. thanks for the help i'll get there in the end.

[greenie60]

dropped the passenger knee bolster and felt that the heater pipes going to the matrix are hot so i'll start looking at the stuff naki suggested.
thanks

[naki]

Does your control panel light up at all? You may need to check in the dark to see. There should be ted lights illumated when you press the switches.
They can fail outright.
If you have lights, but not fans at all, it may well be that the Darlington Transistors have failed outright. They all go eventually from age/ regardless of mileage.
It’s a DIY job to change them.

[greenie60]

I've noticed that when I turn the heater fan on the red 'AUTO' light comes on. if I press the 'MODE' button the auto light still is on and nothing I do can get it off auto. is this correct, should it go to auto straight away like that ?

[greenie60]

well its been 4 months since I posted my query about the lack of heating in my Daimler '40'.
I've dropped the knee pad on the passengers side and stripped out the old 80's alarm/immobiliser (see post) in the process but yup, all it was in the end was the dreaded heater/vacuum valve behind the engine.
I did the checks suggested and found one heater pipe warmer than the other. as I took the old one off it was crumbling with corrosion . new valve from martin robey, job done
thanks all

[greenie60]

the heater now works but is on 'AUTO' all the time and when I press the humidity buttons nothing illuminates.
any ideas please