Thanks Sparkenzap. Is that diode in the motor housing? I put the 12V on the leads going directly into the motor.

 

Yep. Several folks have reported messing theirs up while testing. It will probably work fine without the diode, since it is mostly there for radio noise, I assume.

If you think you have a bad pump, I would certainly give a shot at disassembling it and changing the brushes. I found my brushes years ago at a little hardware store in Jonesboro, but their stock is hit and miss. Getting the pump out is pretty easy on a X-308 with a 1/4 socket and some extensions. Just be careful to not drop the nuts.

BTW, the brushes are not a precision fit. If you can find some that are close, but a little large, you can file and sand them to fit.

 

Thanks Sparky. I c/n do the math so became a mechanical engineer not electrical. I enjoy learning about these electrical things. Do you think the diode is in the motor body, I put the voltage to the leads. I have already wrestled the pump out but will check the electrical drawings - statistically I had an even chance of applying the voltage correctly. Can one know which terminal is + or - on the connector? I pulled the pump at night in the rain and cant say if the wires are designated.

 

The wires are definitely designated. As you can see on the schematic, the ground wire (-) is shown as Black, and the Positive is shown as yellow with a white stripe. (BTW, Notice the Diode) You could measure the car side of the connector and find that one side has zero volts and the other has 12 volts when it should be running, as defined in the service manual, quoted

"Located in the same area as the water valve, the water pump continually circulates coolant through the heater matrix except when the conditions below apply:
The engine coolant is below 16°C .
The ignition is OFF.
Under engine stall conditions, when ignition is ON.
Control panel OFF"

If you do not find 12 volts there, then you are most likely looking for a fuse or relay.

 

Backside of impeller in my hand shown and worn spot on separation plate.


Heater not working so now I think the follow is the way to trouble shoot.
1) Check fuse and relay. All the relays are the same so if you swap the horn relay with pump relay and the horn works - pump relay OK.
2) Pull leads off heater solenoid valve and put 12VDC and listed to see if it actuates.
3) Pull leads off pump and hook 12VDC and see if pump works. There is a diode there that prevent the motor from running backwards and keep the current in one direction. After I removed my pump I repeatedly applied the voltage backward without damaging the motor.
4) So if all this works in theory I should have heat unless the main computer is not sending a signal to the relay. In that case a jacket is likely much cheaper than a main board. Dunno.
5) I had already pulled the pump because I did not know the diode was in the motor. So when I tested it and applied the voltage backwards it did not turn making me think the motor was bad and thus pulled the pump.
6) Now, I do not know if the impeller is any good. Turns out the motor and impeller are magnetically coupled. The impeller is always in the glycol/water mix so there s/b pretty good lubrication. However I find a well worn spot on the separation plate and though the impeller turns, I can't say what sort of head it produces. Any advice is appreciated to know if this wear is acceptable - see pix attached. I guess I am going to rig something up tomorrow to see how the impeller functions on a test bench with water piped into it.
7) I will also flush with air and water the heater core. Hopefully some gunk will come out.
8) If no gunk comes out I guess I will have to assume the impeller is hanging up and I need a new-used one for $175.00 - a new-new one is over $400.


Any/all advice is welcomed before I finish my tinkering tomorrow.
Thanks

 

You are giving very bad advice. The print shows the correct connection of the diode and anyone with the slightest understanding of how a diode works will understand that applying power backwards will short through the diode. Maybe you burned yours open, maybe your test battery was weak, but either way, you are lucky to have not burened it up.
But, carry on, my man. Just don't give others bad advice.

 

The EASIEST way to power the pump for diagnosis is to 'JUMP' the heater pump relay (#1 relay, engine compartment fuse box).

Use a short length of wire to 'jump' between terminals 30 and 87 (#3 and #5 if the relay is numbered that way).

This way the polarity is correct AND the fuse is still in the circuit to provide protection.

Just listen for the pump with KEY-ON-ENGINE-OFF after the relay is 'jumped'.
You can put your hand on the pump to feel the motor run if you cannot hear it.

bob gauff

 

sparkenzap - you could be right. Most of my practical knowledge is low voltage - ie 600VAC or less. A diode is an electrical check valve. In the case of the car, multiple inductors are on the same bus. Therefore it is less expensive to use diodes than individual 'home runs'. On research, the tiny electrical flux back to a solid state board is an additional reason for a diode. What is true is jaguars fully deserve their reputation as unreliable and temperamental POS'.

 

Frankly sir, most of us on here do not regard Jaguars as a "POS". You might not either if you would stop being so pig headed and try and learn something. There is still time!

 

Frustrated at XJ, but I got the heat running pert the following steps. It is truly an exquisite machine.


1) Clear self diagnostic code thru the temp interface on dash and rule out damper issues 2) test fuse and relays for pump 3) put properly polarized 12 VDC on connection to pump & solenoid - repair as necessary 4) back flush heater core or system 5) add coolant as necessary

 

Attah boy, I knew you could!

 

The pump in this case is made by Denso, Japan. Not Jaguar. The diode in this case is known as a flyback diode. It is to reduce large voltages that would be generated by the inductance of the electric motor when the brushes commutate. As current is flowing in an inductance, any attempt to interrupt it causes a voltage change much greater than what was powering it. It is there, through good electrical engineering in an effort to protect other components on the electrical bus. There is nothing temperamental or unreliable in any of my Jaguars. I have 300,000 miles on my current 3 jags and none have left me stranded or had any significant issues.

 

It would sure be nice if Mr. Jawvdp reported back with his results!

 

Spark - what did you say about he XJR I am considering yr 2000. I just looked at it and the paint is so good it must be repainted. It has several of mis-fire codes (inc 0300) and restricted performance was on. The rear RHS area near gas cap is sticking up like it was rear ended. Its on Craigs list in ATL for $4500 but I think he will come down at least to cover a set of coil packs. Dunno if I ever want ot get a car fax.