Have you tried driving the car yet with the new thermostat? Or have you just been testing at idle in your driveway?

The reason I ask is bleeding the system is kinda temperamental. If you still have air in the system (easy to do), the primary symptom is erratic heater operation, especially at idle. I've always just driven the car after any maintenance requiring bleeding, and then top up the coolant. Works just as well as the specified bleeding procedure.

I'm also reminded that the heater worked for your son. Any chance he's got a lead foot? That was with the failed thermostat, too. Makes me wonder how the heater will behave after (spirited) driving for a day or two to complete the lazy man's bleed procedure.

 

Drove the car with new thermostat and was rough on her. I bleed the car just like you do. Tell tale sign of air still in system is the cooling fan running at high speed. I was able to get the car fully bled before starting on the climate control keeping the erratic heater operation in mind. Now thinking of it bleeding it this time was a PITA since heater is supposed to be on high but no actual coolant going past the DCCV.

His version of the heat working and ours is totally different I guess. (I only siphoned off a bit of coolant to get the thermostat changed out) but I will be driving her hard tomorrow and Monday to see if I get a "pulse" from the heating system but I doubt it, especially if the solenoids are seized shut.

Hoses going to DCCV are nice and hot but nothing post DCCV.

I just ordered a Motorcraft DCCV. Dreading having to do this again,

But... I will be tearing down the DCCV after removal to see what the root cause(s) of the DCCV failure...

 

Interesting thread. My thoughts......

Some obvious but still like to share.

Coolant level low, but I'm sure op has checked this. Expansion tank split.
Thermostat sticking.
DCCV. As he's tested it and it's not working I'd be inclined to suspect faulty wiring. I know it's beenmchecked but I would run jumper wires from relays to pump and DCCV. I worked at a dealer and we had s types just a few years out of warranty with wiring failures. A wire can show continuity but not carry any real volts.

You mention the harness under the bumper, I seem to remember the failure point was in the wheel arch area part of the loom.

Blocked matrixs' will also stop flow giving a similar type fault.

Has the engine water pump been updated.


What happens if you rev the car at a standstill and put heat upto hi.

 

Thanks.

Going to replace DCCV tomorrow and flush matrix.

Coolant level perfect, thermostat just changed on Sat (it was lazy), new style water pump, new expansion tank and radiator, new aux pump. All installed in different intervals over past year. DCCV - 2 to 3 mos ago.

Properly bled after each part change. I Use proper OAT coolant.

Pressure tested good, no leaks.

DCCV solenoids stuck in closed position, both sides - no coolant past DCCV. ACCM swapped out with known good unit. ACCM removed tested good, no burnt traces.

Checked wiring but not under wheel arch. Did pull front fuse box and checked wiring look to aux pump. Same with DCCV.

Rev car, no heat. Temps before DCCV nominal. Temps under 100 deg post DCCV.

Aux pump runs when relay jumped. DCCV 12+V voltage at harness side confirmed.

 

Good point about potential wiring faults, but would jumpering help in this instance? Aren't the two valves in the DCCV spring-loaded open? If so, unhooking the connector should mimic a command for full heat on both sides. Or have I been giving bad advice?

 

Your advice has been dead on.

Disconnecting the DCCV harness essentially releases the spring loaded solenoids which allows coolant flow (unless they are stuck closed which I think mine are)

My replacement DCCV came in yesterday (genuine Motorcraft unit) default is open coolant ports...

I will have a definitive answer to this once I remove the DCCV tomorrow.

 

So can you check relay switch wire for aux pump ? If you haven't already.

I have read the posts but it seems you have tried a few different things at different times. And maybe your thermostat fault wasn't helping with diagnosis.

 

ACCM sends an earth to run the pump. Easy to test with a meter. Or bridge relay. If pump runs it's the wiring or module. There's an connector in the loom, would be worth checking.

Www.jagrepair.com is a great source for wiring diagrams. I'll look to see where loom connector is.

 

FC3-2 16 WAY green facia to front harness (see pictures for location) check pin info for correct Id of connector.

 

I tested voltage at relay and installed a jumper between pins 3 & 5 on the R5 relay and aux pump ran.

Good point I'll check that connector in the loom for sure. The lazy thermostat was throwing things off in the beginning (when I was checking coolant temps) but made me pay close attention to temps and clearly the thermostat stood out like a sore thumb midway..

Thanks for the feedback, much appreciated.

 

Before you remove the old DCCV, you could electrically connect the new one and verify how it responds to control inputs. Manually set the temp to LO and both sides of the valve should be commanded closed (steady 12v power). Manually set the temp to HI and power should be removed so the solenoids relax and open the valves.

As far as the power to the aux pump, I still wonder if the controller is missing an important input, such as seeing normal coolant temp. The need for this input is strictly a guess on my part, so don't read too much into it. But still, the controller may have been programmed not to run the aux pump until the coolant was at normal operating temp.

All I'm trying to get at is not to get too bogged down trying to fix the aux pump circuit just yet. Fix the known problems first (thermostat, which you already fixed, and the DCCV) and then see if that also gets the aux pump back, too.

 

Will do, thanks

 

Ok, so I finally got around to installing the new DCCV last night in my 28 degree garage (not fun) I pulled the DCCV and both solenoids were about 85 - 90 percent shut. So good sign, solenoids stuck in closed position.

Installed the new DCCV and I swapped out the aux pump (which I think started to leak) for my known good working one and reinstalled all. Didn't have time to flush out heater core or field test the DCCV.

Started car, bled it best I could. Still no heat. Left it to this morning.

So, I found the gasket to the cap of the thermostat housing (I have the aluminum set up) was not sealing right and leaking. Rigged a new rubber gasket from a PCV grommet laying over in my parts bin from a 78 Trans Am. After trimming it fit the cap recess perfectly and sealed her up good.

Started bleeding again. (DCCV connector "connected") driving, bleeding, driving. The cooling fan was blasting. DCCV pipes still ice cold. Left it to cool off and burp naturally. Opened bleeder screw, eventually stream of coolant came out but it was luke warm, still no heat.

Tonight, disconnected the DCCV connector, started up car and tried to bleed again, no dice. Fan still roaring. Finally. I took the expansion tank cap off and revved the car to about 2,500 rpm and finally, finally heat started coming out the floor vents.

Of course once back at idle the heat went away.

Put cap back on and drove it and it was borderline about to overheat. Little heat, fan running fast.

Shut car off, pulled out the R5 relay, jumpered terminals 3 & 5 and aux pump burped and started running. Started car - blazing heat, coolant in expansion tank finally went down and fan went back to normal speed.

Drove it, nice and toasty.

To Recap:

a) Replacement DCCV installed and working (plug disconnected currently) Old DCCV solenoids seized shut - both sides.
b) Aux Pump works when jumpered at relay. Otherwise, not operating.
c) Heater core not blocked.
d) ACCM that is in car still questionable I guess.
e) What will happen when I reconnect DCCV plug?

So... Now how do I proceed?

1) Now that I know the air pockets are finally purged from the heater core and the core is not blocked if I reconnect the DCCV plug will I retain heat and maybe, the aux pump will kick in and start working as designed? (Doubtful)

2) I still have another ACCM I can swap in. Again, did it before - maybe the ACCM in the car currently is shot?

3) I have to resort to looking at the wiring loom and that "connector" that is in the loom that was mentioned in this thread.

4) I'll throw this out there but what about the module that is attached to the fan shroud? I only ask as the DCCV plug is associated and feeds off of it...

Making progress but this is kind of boggling me.

Or, I'm going to run a switch in the cabin for the aux pump and leave the DCCV connector "disconnected" and call it a winter....

Thoughts?

 

Have you cleaned your cabin sensor?

Link http://jagrepair.com/images/AutoRepa...s/STypeAC4.jpg

 

That is normal if the aux coolant pump was not running at the time.



Which fan? The radiator fan? If so, that means the coolant temp sensor is working, and was telling the PCM of the impending overheat condition, which then commanded the radiator fan to run for extra cooling.

Or was it the HVAC fan? If the temp selector was in auto, that might indicate simply not enough heat being sent into the cabin. As smart as the climate control system may be, it's also very stupid. It's expecting to see the cabin temperature rise as heat is added. If it doesn't, the system commands more heat, i.e. opening up the DCCV fully and speeding up the fan. I'm not sure the system is smart enough to realize it's pumping out cold air when heat is commanded. This may be a normal side effect of the aux coolant pump not operating at the time.



Great troubleshooting. Even if it may not seem like it, you're making good progress.


Definitely worth a try. If this doesn't help, investigate the command signal to the DCCV. You can always unplug the DCCV and get back to where you were.


This is a good possibility. The ACCM commands the aux coolant pump as needed. I think it also sends a command to the PCM to run the radiator fan when the AC compressor clutch is engaged.


This seems less likely. I'd keep that idea on the back burner for now. The ACCM seems like a much more likely culprit to me. On the plus side, you have a spare one, too. If nothing else, I'd try that first simply because of that.

 

Good suggestion. I think if you run the system in manual mode, the sensor is out of the picture, which will help with troubleshooting.

 

Yes sir and checked output via IDS - on the money.

 

Yes, the radiator fan and correct I can tell the engine is running hot when the fan is running higher.

Karl, I have run the system in manual mode throughout "hi" on HVAC display.

Thanks guys!

 

I've gotta pause for a second here. Does the dash gauge and your scanner also show elevated coolant temperature? I just want to make sure the "running hot" diagnosis isn't based solely on the radiator fan speed.

Good, this is helpful to know.

 

Are you sure all the air is out of the coolant system? When I purge the air out of my xk8 and S-Type all I do is squeeze the top hose gently and listen for air escaping to the fill cap. You will know when it is full.