Hi Guys,

I replaced my DCCV about 2 months ago. I properly bled the cooling system and all was working with the heat. I went out the other night and it was a bit chilly and I raised the temp to 85 degrees.

About 10 minutes later I noticed that the air coming out of the vents was ambient temperature, no heat whatsoever.

I really didn't worry about it but dug into the issue today. Here is what I did:

Checked relay - good (swapped out for another relay - no change)
I cannot for the life of me find my handbook that shows fuse locations and the net wasn't much help. (I checked each fuse in the engine bay fuse box - all good)

I then checked for voltage at both the aux cooling pump and DCCV - zero volts!

I then left the DCCV connector disconnected to see if I would get heat. I checked the temperatures on the aluminum lines. Two smaller lines were between 100 - 115 degrees and the main line was above 130 degrees.

I have a spare, working CCM - swapped it out - no change.

I then pulled out my Matco Determinator to see real time HVAC data. I attached a pic. Now the car was cool and the weird thing I noticed was the driver and passenger sensors were reading 147 - 152 degrees! (55 degrees outside, sunny and showed those readings as soon as I started the car from cold)

Now I have codes for floor and recirc servos (but I've had them for quite a while)

So, either:

Electrical wiring fault (or maybe I missed or didn't look at a fuse elsewhere like passenger cabin)

Evap sensors (driver's and passenger - both shot)

Blend Door servo bad and it's locked in position blocking flow of heated air into cabin. (Didn't get a code for it though)

Any feedback would be appreciated before winter sets in...

Thanks - Anthony

 

Unlikely either temp sensor let alone both failed so maybe reporting tool doesn't work or else some common cause (bad connection / chafed wire / ...). I think you could check a sensor fairly easily for plausible / dead (meter with sensor still in circuit and blow on the sensor, meter should see something). (But it'll probably show the sensors plausibly work as they probably do.)

I think if the CCM (due to bad inputs) sees cabin is warm it'll not blow in more hot air. So even with DCCV on default (should be hot) you'd have no air flow.

I can't recall what aux coolant pump does (is meant to do) on your car, sorry!

 

Good point. This tool has been very accurate historically. Going to use datalogger via IDS and see if I get similar readings for those sensors.

 

Aux cooling pump provides heated coolant at idle.

I looked at sensor readings via IDS datalogger.

All evap and temp sensors look good and are close to each other temperature wise: 70 to 90 degree ranges during testing (all within 0.5 deg. of each other)

Aux Pump - off at idle (should be powered on) and DCCV - 0% duty output both sides throughout testing when commanding heat. No output whatsoever even when changing temperatures. (Basically no voltage to either) - clearly explaining the ambient air coming out of vents. I don't believe there's a blend door.

I had a code for Internal CCM Failure (the other CCM I swapped in yesterday for further testing probably is toast as I put the original one back in when I had the same no heat outcome) I erased the code and it didn't come back during testing.

I'm wondering if I have a wiring fault cutting power to these two items (they seem to run on the same harness) or maybe the CCM is not commanding these items on. (internal issue after all?)

If I read correctly the aux pump, DCCV and AC Clutch are on the same electrical circuit. The AC clutch is working and powers up when commanded.

Found my owners manual!

Checked Fuse 1 in engine bay (for aux cooling pump) has power and checked fuse #14 in passenger cabin (air climate control module) - also good.

Leaning towards a wiring issue.

 

Good work and it looks like the AUX pump is not working.

Just a comment as I also had little to no heat and never did find anything wrong. I replaced my AUX pump anyway with no change. Brutal finally suggested I flush the heater core. Never saw anything come out of it and I flushed it forwards and backwards as with a spit heater core like we have you really can't do a proper flush.

Well I got my heat back and still can't explain it because I change coolant and everything was very clean inside the cooling system.
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I have a spare aux pump. I also changed the aux pump when I serviced the DCCV.

I'm going to check the harness that runs under the front bumper. I heard the early S Types had harness issues under the front bumper.

The plastic that protects the wires broke off ages ago. When I was under there I added electrical tape so the wires wouldn't continue to be exposed (although the under carriage plastic shield offers some protection)

I also noticed the specific harness runs across the top of the radiator and there's a section that fits tightly.

Going to start here as my guts telling me it's a wiring issue since the heat worked brilliantly after bleeding the system. Then I'm going to check the CCM.

Regardless, I'm going to attempt to flush the heater matrix also..

 

In case I missed it, sorry, but otherwise you can test the DCCV easily and then force it fully open (via appropriate power - I think you just remove the power) to see if you get heat.

 

Hi JagV8 - I did disconnect the DCCV connector. No change. The weird thing is zero voltage going to both the DCCV and the Aux Pump.

Confirmed with IDS and voltmeter. Fuse/Relay has power. Going to check the wiring harness that runs under the front bumper and pull the insulation back on the harness that runs across the top of the top radiator hose.

I have played with this harness several times over the past year moving, connecting and disconnecting the harness connectors to perform the following tasks individually. (Radiator fan motor/shroud replacement, radiator replacement, AC manifold hose replacement, and DCCV/Aux Pump swap)

Maybe a wire/ground is broken within the harness?

As we all know these harnesses are hard and brittle...

 

Well yes something odd if no volts - chafed wire, blown fuse, bad relay, etc - but I believe DCCV should be open with no volts.

So if you still get no heat maybe the aux pump not running would account for that? (As you know, something needs to....)

I think it was later models than 4.0 that had factory-caused harness problems, but of course you can still have a problem by now sadly.

Maybe disconnect DCCV and aux pump then run a separate (fused) feed to power the pump for testing and see if you get heat. If you do then I think we know what works & what doesn't - just not the details of why and a fix as yet.

 

This one is a headscratcher. I don't think an electrical fault is the root cause.

With the plug disconnected at the DCCV, it should put out full heat. The two valves inside the DCCV are spring loaded to the open position. While not impossible, it's not very likely a new DCCV would fail right out of the box, especially since the symptoms didn't change.

Did you ever try setting the temp to HI? That puts the system in manual and bypasses much of the automatic system. I'm kinda doubtful this will do anything since you already had the connector off the DCCV, but it's easy to try.

How about the actual coolant temperature? Perhaps the engine is running colder than indicated (thermostat problem?) so there is inadequate heat energy available to transfer via the heater core. Keep in mind the dash gauge is deliberately dumb. Within a broad range, the needle is centered no matter the actual coolant temperature.

I'm still puzzled about the missing command to run the aux coolant pump. Is there some logic that looks at coolant temp and only runs the pump if cold?

 

hmm, not sure that's right for cars which have an aux coolant pump as his does. They're fitted for a reason...

IIRC aux is on all the time (same as SC one for my car).

 

I may be less correct than usual on that one. I thought it only ran at idle but now am not sure.

 

I confess to not having checked the actual circuit as it's a car I don't have.

 

Ruined my dinner, thank you very much... Kept thinking about this one the whole time, trying to remember where I'd seen the details. This is from a 2002 Jaguar Climate Control Training Manual:



No mention of the differences with the SC models, however. Hopefully this excerpt is of some help for troubleshooting.

I'm still leaning towards the coolant not being hot enough. The way I understand it, an inop aux coolant pump (whether from a failed pump or no command to run) would only show up as low heat at idle, but be okay at higher RPM.

Can you get an infrared thermometer reading somewhere on the cooling system, perhaps the radiator inlet? Try one at idle, and another after a hard run that should have the coolant at normal operating temperature. My hunch is if the thermostat is letting the system run too cool, the temp will drop even lower when in motion due to all that extra airflow through the radiator. That's my story, and I'm sticking to it. Until something else comes along. Look, a squirrel!

Don't forget to try setting the temp control manually to HI.

 

Guys,

Thanks for the input.

I did run the system on "hi" - No change in temp air coming out of all vents between 75 - 85 degrees. Infared temps of DCCV lines around 100 - 105 at best. (On hoses) metal lines around 95 - 100.

Engine temp showing between 194 - 205 at full warm on IDS.

I checked out the wiring to aux pump this evening. All seems to check out good. Power at fuse #1 and relay. Still no power at harness, failed continuity check.

I cut back the harness shield back to where it was tight along the radiator shroud. Wires looked good. Went underneath the car, plastic retainer that holds all the wires is partially gone but checked the wire for aux pump, looked ok surprisingly..

I also checked the harness under the front distribution box (which I will never, ever touch again thanks Jag/Ford plastic tabs) - that checked out good as well.

I'm going to study the electrical schematic for the HVAC a bit to see if I can figure the following:

Wondering if the CCM commands power to both the DCCV and aux pump to run?

I also noticed the DCCV harness runs to the cooling fan module and the aux pump wiring runs back to the front distribution box, so they are technically separate but I'm sure they both wind up together again at fuse #1 and R5 relay.

I think I'm going to have to bite the bullet and purchase another DCCV (Bosch) and install it and flush out the heater matrix too (which I didn't do but I religiously drain and replace with proper OAT coolant).

Now that I checked the wiring and couldn't find anything obvious I have to now focus on DCCV (possibly solenoids seized in the closed position) and possibly CCM internal fault.

It's frustrating that these would come bad out of the box but I've heard it happens.

I will keep everyone apprised.

 

Do you still have the old DCCV? Can you tell if the 2 valves failed open or closed?

For troubleshooting, how about this crackpot idea? Can you physically rig the 2 valves open somehow? I know changing the DCCV is a pain, but install this guaranteed-open DCCV and see what happens (Leave the connector unhooked). No need to bolt it down as this is just temporary. If you now have heat, you know the heater core isn't plugged, coolant is hot enough and flowing properly, etc.

Just a thought, but a couple hours of your time may be worth it to make sure you really need a new DCCV.

 

The old DCCV was leaking from the metal cover bolts, but functioning.

When I took the metal cover off both solenoids were filled with coolant. Both valves were open if I recall correctly.

I chucked it in the trash, unfortunately.

I guess the troubling point for me is IDS showed both solenoids essentially closed (0% flow output) with harness connected.

Is 195 - 205 deg. (60 degrees ambient temp) considered normal operating temp?

I wonder if I can open up the cover on the current DCCV and see if the solenoids are open or closed?

The aux pump was bench tested before install.

 

Sorry!

Turned out to be useful, though.

 

hmm... IDS seems odd there. I expected it to want the valves open.

It can't of course tell if the valves do actually open.

Would be a bit unlikely for the DCCV to have BOTH valves fail - and closed. They usually fail one side first and open.

I think that temp range is likely OK (JTIS has the range as I recall). I work on "nearly boiling" (if water and unpressured, neither of which apply but it's what I have in my head). PCM tries to run it hot as it's lower emissions and better MPG.

Maybe wire the aux pump on, expecting heat from at least one side of the DCCV. (I had a look at the elec guide and yes there's a relay.)

 

The IDS reading is confusing, to say the least. In post #1, you mentioned no voltage at the DCCV. I believe that is what you'd want to see, as the valves are spring loaded open.

However, if control is by pulse width modulation, an ordinary voltage reading may be misleading. That's why I suggested leaving the plug off for troubleshooting, so the valves would (hopefully) open regardless of the command.

I also fear I may be inadvertently misleading you with my ideas. Maybe just take any of my suggestions with a grain of salt, in case I'm once again less correct than usual.

For the coolant temps, my '02 V6 usually runs around 220-230 per my scan tool. On the slim chance your temp sensor is out of whack and erroneously saying the coolant is where it should be, can you try a thermometer reading at the radiator inlet? You've already confirmed the lines are cold to and from the heater. The next step would be to confirm the coolant temp somewhere on the other side of the DCCV.

Other than that, I'm stumped. Sadly though, that doesn't seem to stop me...