Heater failure

[J44EAG]

Guys,

Help appreciated.

J44 suffered heater tap failure at 44k miles. Typical S-type fault - full cold.

Valve unit replaced and ok for around five years until last summer when the heating system went full hot. Turned the blower off and have generally run with the sunroof partially or full open to let the fugg out.

Last night the heating failed completely at 81k miles. No control at all.

Has anyone had this experience and what caused the problem. Heater valve again?

Mike

[Montana5]

This is something I have not had to deal with yet, but this is what I would do.

Mike...assume that you have tried all the cabin sensors and outside temp sensor, so looking at the Valve itself, yours should be the 5 pipe valve, a couple of things to try...

Any symptoms with the HVAC Panel not lighting up.

Stuck valves can sometimes open and work after a few blows to the valve with a hammer and screwdriver.

When warmed up, feel the Pipes going in and out of the DCCV, pull the electrical connector plug out, I think its held on with a strange clip, do any of the previously cold pipes get warm, does the cabin get warm.

Missing power supply...keeping connector plugged up, use needle probe on multimeter pierce each of the 3 wires going into the plug to check, set AC to low temp voltage on middle wire should be +12v, voltage on 2 outside wires should switch between +12 and +0 volts as climate control tries to adjust temp, if the two outer wires remain at +12v permanently its likely that the Climate Control Module, is never commanding the DCCV to close, which means its an electrical problem.

I believe earlier models are less likely to have the corroded wires as seen in newer models.

It is just possible that you have the dreaded Climate Control Module circuit board burnt tracking problem, Jaguar in their wisdom did not fit any overload current protection to the Climate Control Modules, so when the DCCV sticks or seizes, the Control Module keeps on trying to power up the Valve and eventually the circuit overheats and burns the component circuit board, easy enough to re solder or by pass the burnt tracking with a piece of cable, as long as not too much damage is done.
I hope its something simple and you get it sorted without too much bother.

You know about the diagnose it yourself site, lots of useful info on there.

Doug.

[J44EAG]

Thanks Doug.

I need to get under the car which is not easy here due to lack of facilities and low 100mm ground clearance on J44. I might just have to give it to a local guy to do.

As you say the module car burn if valves get jammed. I believe it is located behind the glove compartment.

Thanks for the advice.

Mike

[Martec]

Hi Mike, how is it going with your heater valve/CCM?

I've been looking at the wiring diagram for the early cars (1999 - 2002), fuse 32 (10amp) in the front fuse box supplies both the heater pump and the heater valve and from the diagnostic article (too good to lose so I've copied it) each solenoid should only draw '0.6 - 0.9 amps'.

Would it be worth adding an inline fuse of 2 amps to the centre terminal (+VE) to save over current to the CCM? If the fuse blew then the resistance of the coils could be measured to to find the current draw.

I realise this shutting the barn door after the horse has bolted.

Brian

[J44EAG]

Thanks to both Doug and Brian for their advice.

Undoubtedly the valve is probably shot. Was working partially prior to the total heating failure the other day.

Continued using the car then a full temperature gauge deflection occurred as I headed north out of Portsmouth up the M275 motorway. Fortunately I was able to do a left swerve off the start of the motorway onto a petrol station forecourt complete with water tap.

I added a litre or so of water to the previously installed strong antifreeze solution, ran the car up, burped out any air and made it home with heater once again in action. Very odd to loose coolant and something I haven`t had time yet to investigate. Loss of heat in this case was down to coolant loss.

Since the new water pump, thermostat and temperature sender saga of last year, things have been quiet. Then the heater loss, coolant loss and my very rapid limp home.

Nothing showing leak wise in header tank or other areas showing on the ground. Easy day tomorrow, so will have a poke around and see what I can find.

Watch this space. My mayhem usually gets worse before it gets better.

Mike

[Martec]

At least it isn't the expensive CCM (fingers crossed).

Just out of interest the fuse No1 in the forward fuse box (or at least on my early V6) is 10amp, this is supposed to supply power to the heater valve, auxiliary heater pump (V8 engines - not V6) and relay plus the A/C compressor clutch.

As the early V6 and early V8 both have the 10amp fuse this will allow the same heavy ampage to the CCM. Is it either auxiliary heater pump or the A/C clutch switched on??? if not then a smaller fuse could be fitted to the V6??

I had to use a mirror on a stick and small LED light on a stick to see the heater valve connection(god knows how you get meaty hands to it), but the cable rises and moves to the centre of the grill so it is feasable to fit an inline fuse.

Brian

[Montana5]

I can see where you're coming from Brian, however I believe the in line fuse would really have to be fitted at the Module side, the high current and eventual heat as you know are coming from the printed circuit board, fuses react to high temperature as well as over current, so in my opinion a fuse at the Valve side would blow/rupture a lot later, where as a fuse at the Module would detect the current and heat through the conductor wire much quicker and blow/rupture before the soldered track on the PCB is damaged, you could always go belt and braces and fit a fuse to both ends.

Doug.

[J44EAG]

Good stuff, guys. Most enlightening. Please keep the gen flowing.

Mike

[Martec]

Interesting comment Doug.

Working on old world values then current runs from positive to negative, but infact is the reverse so manufactures are begining to change from positive wire switching to negative wire switching, is this where your coming from??

So far I've seen the early S type has both, the reverse lights are negative switching hence having to fit a relay in this circuit. The heater valve seems to be the same, what I think is a live feed +12 volt to the centre pin and earth switching at the CCM for the two outer pins.

I can see problems in keeping a single 2 amp fuse near the radiator dry, but the two earth wires to (from) the CCM would need two 1amp fuses. The trim panel on the dash side is one I haven't removed yet so don't know how much room there is, also from the early wiring diagram they are contacts 11 and 12 at a junction block and 5 and 6 at the CCM.

I have no indepth knowledge of electronics (I struggle) so assumed the heat was a by product of current flow on the board, so take your point.

Something to look at tomorrow.

Brian

[oldtimer]

Hi Brian, Doug and Mike,
I have been re- reading this thread for the umpteenth time.

All the logic makes sense except;-
I know of two types of solenoid. The first and most common comprises of a coil of thin copper
wire and when a current is passed through a magnetic field is created. this in tern pulls the iron core to its centre. Hey presto some mechanical movement is achieved. The second type employs two coils. When the devise is switched on both coils are energized. The primary coil or pull in coil draws 40amps and the secondary or hold in coil draws approx 1amp On this type of coil a pin is attached to the end of the moving core and when energized and operates through its full travel the pin operates an off switch leaving the secondary coil to hold the core in position.

I suspect that the first type of solenoid as referred to above is used in this application.
As Brian points out this solenoid draws about 0.5 - 1.0 amp load (about the same as a 5-10 watt bulb.)

I'm really guessing now. But I guess the in car temperature is monitored by a Wheatstone Bridge (spelling)comprising of three arms of resistances, one reading in car temperature (thermistor) another reading outside air temperature and the third being the in-car temperature change control. When the temp control is moved the equilibrium is upset so a re- adjustment takes place. These readings will need to be amplified within the control module in order to operate the solenoids.

The above is me just burbling to myself.

The Amplified signal will be sent out to the appropriate solenoid coil saying more heat engineer.
The coil will remain live until such time as it is instructed to shut down. The coil does not give a "toss" if the core moves or not and has no bearing on its longevity.

It would be interesting to have a bulb wired across the solenoid and back into the cabin to see the frequency at which the water valve/solenoid operated. I would suggest that in very cold weather the solenoid remains energized most of the time. Guessing again!

OK then folks, do you agree or is this a load of old tosh. If you do agree, the theory put forward is flawed and need to go back to the drawing board. If you don't agree , that's fine but only if you support your reasoning

Meanwhile Mike have you got a working heater and what was the fix

Phil

[J44EAG]

Brilliant, Professor. Thanks old pal. Oldtimer engineer to the last.

What you say makes eminent sense. As always.

Regret, no, my fault not fixed yet. Battle between need and value of car. The old XJS has more systems working than J44! Suspect my heater operation problem is either a burned out thingy on the control module, or something akin to Brian`s recent post about fuses and behind front bumper wire issues). I`ll probably sweat my nuts off before I fix it!

Then again I have a more pressing problem with the drivers door card on J44. I need new clips, a couple of screws and other wotnots to stop it falling off in the street when I shut the door. This and my new floating workshop has stopped me fixing these problems!

Hijacked thread!

Back to the thread again. keep at it Phil. Great research. Would be good to see some of this on our pages in the magazine.

Mike

[Martec]

Looks a bit draughty mike?

Brian

[J44EAG]

Full of rain water again today due to diabolical weather conditions.

Rain stops play again. Fought conditions yesterday attempting to epoxy prime ten sections of plywood to infill the sides. Still, the weather looks fair tomorrow.

This floating heap of former marine excellence came to me for a song. Interior rotten, engine water damaged, rudder fallen off and skeg hanging off. Work benches, washing machine, Jag seat and other facilities being planned. One of my better buys.

Mike

[Martec]

Don't forget the wine rack and bottle bank.

Brian

[oldtimer]

Hey Up Mike
That's a fine looking hull, is it wood or fibreglass?
I reckon the V12 out of the XJ would fit a treat