I have a XK8. 2002 model. The coupe heater has not been working so I changed both the heater pump and the valve. Still not working. When I set 12V direct on the pump it runs and the heater blow warm air as it should. My understanding is that the pump should start immediately when the ignition is turned on. Is this correct? Or is it controlled by the A/C control module? And what is regulating the magnetic valve allowing water to flow through? The A/C control module? I have checked the fuse for the pump = OK. So where is the missing link??

Bengt

 

Pump runs all the time ...flow controlled by the valve behind the expansion tank. It could have no supply or be stuck. Put controls on max heat. Not much else to the system but that.

 

Hi.

Thanks for your reply. Issue is that the pump do not run when engine is turned on. With direct supply of 12 V it runs then I got heat into the car. The valve is not stuck. Fuse is ok, where is the short? 😂

 

If Fuses #3 (5A) and #15 (10A) in the engine compartment fusebox are OK, then check the heater pump relay in the same fusebox:


You can swop it temporarily with one of the other brown relays

 

The front fog lamp relay is right next to the heater pump relay. I believe it has the same pin-out as the heater pump relay. If so, try swapping those two relays to see if the pump comes alive.

Here's the circuit for the heater pump. The circuit is protected by engine compartment fuse box Fuse #15 (10A):




Also, the ignition-switched power circuit 58 is protected by engine compartment fuse box Fuse #3 (5A):



You can download the wiring schematics for your 2002 at this link, thanks to Gus who hosts his jagrepair.com website and motorcarman, a former Jaguar dealership mechanic who supplied the documents in pdf format:

Jaguar X100 Electrical Guide 2002

Another common issue that affects heater performance is a stuck-open engine coolant thermostat. If your engine is slow to warm up or runs a little on the cool side, suspect a stuck-open thermostat. The temperature gauge in the instrument cluster reads in the middle position between around 82°C/180°F and 115°C/239°F, so it is not useful in monitoring actual engine coolant temperature. A scan tool with Live Data capability or an infrared thermometer aimed around the thermostat housing are more helpful.

One other issue to be aware of is the potential for the heater core to be clogged, especially if a previous owner has intermixed coolants of different types (inorganic, organic, hybrid-organic).

Cheers,

Don

 

If you have fitted a non standard relay to replace the pump relay you will have buggered the final transistor in the ECU.
Let me know if that is the case and I will tell you how to get around it.

 

Hi
Thanks for good advice and also showing me the el circuit for the heater pump and valve. All going back to the A/CCM. All fuses are ok, did switch relays and pump is still not running. Can I now conclude that I need to change out the A/CCM? Another option is to bypass the A/CCM and give the pump direct 12V supply from another circuit? Say the fog lamp circuit. Can then turn on the pump as required??

Comments to this?

Bengt

 

Pull the relay and join 3 and 5 on the relay base and the pump will run with the igniton on.( see diagrams in posts above)
Job done ..mine runs like this no problem as there is a clutch in the motor when the valve is closed

 

Service Training course 703 implies that the pump will normally run when the coolant temp is above 30°C and engine is running. Both of these would be satisfied by normal driving so the issue will be elsewhere.

I'd suggest grounding the Red/White wire in Don's circuit snip somewhere along its length to simulate what the ACCM should be doing. Simply bridging the relay will result in the pump running irrespective of the ignition state as its 'hot' side is permanently at B+.

You can either leave it at that or investigate around the ACCM module at some later point.

 

Hi. Thanks for good advice. First I joined 3 and 5 on the relay, yes the pump started - but ran even if af the ignition was off, as Michael advised.
Under the fuse box there are 4 connectors, white, green,. blue and black. I found 2 each white/Red on the white connector. Tried to short each of the cut ends to ground, pump did not start (after running the engine for 5 min).
Am I missing something?

Bengt

 

OK - that's good because it proves that the power circuit through the relay to the pump is fine. What we need to do now is to get the relay to fire when the ignition is turned on.

Check that you have B+ (~12 volts) on pin 1 of the heater pump relay socket with the ignition on. This will confirm that the relay coil is getting its supply.

Sorry, I'm not clear what you mean here. You are looking for a Red/White wire which connects to pin 2 of the relay. It is this which needs to be grounded. There are some connectors which will clip over the wire and make contact through its insulation. There's no real need to cut anything.

Note that we' re bypassing the ACCM here, so whatever conditions it requires can be ignored:- the relay should operate and the pump start as soon as the red/white wire is grounded (with ignition on). No need for the engine to be warm or running, etc.

 

AS always micheal you are right ...I meant to say 5 and 1 one being an igniton fed live. Pump is only 24 w
I had a similar problem on mine where the ECU would not provide an earth for the relay . So not being happy with the pump running all the time in summer ( though it is designed to do so ) I fitted a relay powered by the wiring to the water solenoid to turn it off when the water solenoid was not allowing water flow, Works fine

 

I didn't realise that the pump was such a low draw - or did you replace the original? That would be simpler than grounding the other side of the relay coil.

I don't like the idea of the pump running full bore continuously either: I'd considered fitting a separate switch. Just need the round tuit...

It would make sense to me if the pump didn't run when the A/C is on, but I can't find anything documentation-wise in that regard. I can't check that atm as my A/C is offline (again, sigh). There are a couple of feeds from ECM to ACCM that might be worth investigating before condemning the latter module.

 

In the early days I buggered the output transistor in the ECU by using a non jag relay.
I fitted a change over relay by connecting its coil to the water valve wires and then switched the pump with the N/C contacts picking up a live from pin 1 ie when the valve is not engergised the pump is. I agree its silly to have it running in the summer

Been working fine for months

 

You fixed the heater yet ?? Nothing worse than an unfinished thread just hanging in the air ....hot air I hope

 

Hi
Worked a bit with grounding R/W wires, No success. I did find 2 wires that are W/R (red stripes), both connected up to the white connector (as mentioned no success). I gave up and connected the pump direct up to the fog light (for now). Not according to the book - but now I have control of the pump😊 And heat in the car.
Anyway, thanks for all good advice.
Bengt

 

Ah, it's clicked. The white wires with the red stripe are power feeds to various relays via F3.

The one you want is a red wire with a white stripe: it should connect to the base where the relay plugs in, not the 10-way connector.

Yeah, I know - easy to mix up. Reminds me of 'The Abyss' where Brigman is miles underwater deciding which wire to cut to defuse the bomb when they all look grey...