I got the Intercooler pump working on my 06 SV8 and am now looking at the auxiliary coolant pump which does not seem to be running. At least it is making no noise that I can hear when I check it with a stethoscope with the climate control on and the cabin blower blowing.

I checked for voltage at fuse 8 (Auxiliary Coolant pump) and fuse 7 (Blower) which are both powered by Relay 1 (Blower Relay) in the Rear Distribution Box. With the Ignition on and climate control off they both had 1.703 Volts. With the ignition on (position II), the climate control on, and the blower running, they both had 11.87 Volts. With the ignition off they both still had 1.702 Volts. The battery has 12.38 Volts.

I assume that if the blower is running that the blower relay is closing as it should. I'll try to get to the connector on the bottom of the Auxiliary pump and see if it is getting voltage, but in the mean time do these voltages indicate a stuck pump or an open circuit?

I also don't understand these fuses having 1.7 volts with the ignition off and the blower relay supposedly open, and if I remove Relay 1 they still have 1.702 Volts to ground.

And finally, does this pump have much to do with engine cooling in the summer with no heat called for from the cabin heater?


Edit: OK, I can see the auxiliary coolant pump's connector and can even get a hand on it, but I can't feel a release tab. Anyone have a pic of how this connector comes off? Or a description? Meanwhile I'll attend to the big scratch on my forearm from the sharp edge of the frame.

 

Pics of pump connector. Press in on tabs at top of connector near wires and it should pull off.

I do not know the answer to your other questions however if the aux pump was not working you would not have had much heat blowing into the cabin.

Also if the aux pump was not working you might not purge all the air out of the heater core when topping up coolant.

1st pic is of old aux pump that I replaced. It was working however I thought that I might as well renew it while I am reworking so much else. I managed to get one on Ebay "new old stock" for less than $100. Larger diameter tho.

 

Ok, thanks again for helpful pics. So pinch it at the wire end and it should release. My brain grasps the concept, but my fingers couldn't quite follow through having to reach it at an odd angle and that bracket on the radiator under the end of the pump doesn't help either. Guess I am going to have to bite the bullet and drain the system so I can pull the top radiator hose and get at it from above.

I did see several links in the archives to instructions for changing the brushes if it is the pump itself that's bad, so perhaps it is best to remove the darn thing anyhow. I don't want the engine to have any excuse to overheat again and come winter we may need the aux pump for cabin heat.

 

Is there a logical reason the voltage is weak on fuse for aux pump?
Backtracked every other possible symptom and concluded its a fuse or circit issue???

 

Just to simlify things:

If the aux pump is not running there will be no heat in the cabin.

However I have just noticed on my Jag that when the climate is set to 21 or 22 Deg C there

is no heat in the cabin.

Set control to 23 Deg C and I get heat.

I think the pump is failing due to wear of the brushes.

 

Yep, there have been a few threads on that topic. If memory serves someone said they had some success in finding new brushes of the right size, well that would fit reasonably, in model shops.

A search with 'auxiliary', 'pump' and 'brushes' as the search terms should throw up something.

 

Here you go:
https://www.jaguarforums.com/forum/x...-brush-115220/

 

You can pick up a new Bosch pump that will work for around $50.

 

I spent $25 for replacement brushes (I bought two sets just in case I messed one up, but didn't need the second set) and was able to get them installed with as long a brush length I could, so they should last at least as long as the original brushes and probably longer. The rest of the pump was fine. BTW, the Russian method of freezing the brushes in place for reassembly worked great.

 

It could be an issue with the relay; try swapping another relay into Relay 1 (Blower Relay) in the Rear Distribution Box. Fuse 8 (Auxiliary Coolant pump) and fuse 7 (Blower) are both powered by this relay, but be aware that the relay only closes when the ignition and climate system are both on. With ignition off I measure 1.7 volts at these fuses for some reason I don't fully comprehend.

 

May be backfeeding.

 

I'd have to try to sort out the wiring diagram again; With the ignition on, the climate control on, and the blower running they both had 11.87 Volts. With the ignition off they both had 1.702 Volts. The battery had 12.38 Volts. I guess the real question is what is the current, if any, going through these fuses with the ignition off.

EDIT: Looking at my notes again, fuses 7 and 8 still had 1.07 volts with relay 1 removed so that seems to eliminate a relay malfunction, and my auxiliary pump had no continuity before I replaced the brushes which seems to eliminate it as a back feeding source. That leaves the blower circuit as a voltage source for back feeding.