Well your are right to fix this. My 2005 STR A/C blows ice cubes and Friday in Houston bumper to bumper rush hour traffic my outside temperature reading was 102 F.!!

Are you really sure the DCCV is not letting some hot coolant into the core reducing what your A/C can put out?? I would consider temporarily pinching the heater hoses off. You can use pliers like this and it would be a pretty simple test??
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Jon - it's not even vaguely what it should do. As to the reason, diagnostic equipment (such as IDS) lets a dealer look at each of the sensors (temperature, a/c pressure, etc) and decide which if any need fixing. It's the shop's problem, surely. Though... if you get lucky then Brutal may have ideas

 

There are a few things to consider here. The problem could either be on the mechanical side - compressor, condenser, evaporator etc. Or on the electronic control side.

1) Air vent temperature. - The air coming out of the HVAC system should be ~ 50 deg f or colder - you need one of those thermometers with the probe in it to stick in the dash vent for this.

Generally speaking, most modern HVAC systems use compressor cycling combined with running the fan to achieve the desired temp. So how much cold air they pump is based on how long they run the compressor combined with how fast they blow air over the evaporator. But the cold air is at the same temp - it's just how much they pump into the cabin. IF you have the proper temp air, then its something else. If the air is in the 60 degree range or above, there is something wrong with the mechanical side. Basically the temps @ the vents should be at that level regardless of ambient. If it's not, and the temp @ the vent changes relative to ambient, then you are chasing a mechanical problem. If it's 45-50 not BUT it steady relative to ambient, the DCCV may be something to look at, in term of it potentially allowing coolant through the heater cores.

Now, there could be several things at play here. From you description, it seems like the condenser and fan are ok. That usually manifests itself as a warm air at idle, cold air at speed issue.

I would tend to guess that maybe there is some sort of interior temp sensor problem. Whereby the car is registering a lower inside temp than actual, so the hvac is backing off prematurely.

My money is on some sort of reduced efficency scenario - where the A/C can't maintain a constant temp in the vents regardless of ambient. Either it's undercharged - there is moisture in the system (there should have been a vacuum pulled on the system, and it boiled out during the recharge), or you MAY have a kinked line, restricting refrigerant gas flow. OR overcharged whereby high side pressures rise, and the compressor shuts off prematurely to protect itself.

You may also want to listen to compressor /stops starts, as it may be kicking off... Does the car leave the telltale puddle of water under it when the A/C is running?

I just realized I may be rambling, hope this makes sense.

George

 

Guys,

I spent about 20 minutes in the driveway with the S-Type idling and the A/C on maximum cooling. The outside temperature is pushing 90 degrees this afternoon. I don't have a thermometer-on-a-stick to shove down into the vents, but I could tell by feeling with my hands that the drivers center and side vents are blowing cooler air while the passenger center and side vents are blowing warmer air....

This sounds more and more like a classic case of a DCCV that may be in the early stages of biting the dust. No external coolant leaks on it, though. At least not from looking at it from above and wiping it with a clean white napkin....

Do you guys agree? If not a faulty DCCV, what else could it be?

 

Jon,

From everything I have seen, the DCCV either leaks externally with NO HVAC issues, or fails and gives you the hvac issues with no coolant leak. I know its a bit tricky to get to, but you may want to unplug the DCCV electrically. That should open the flow to the heater cores (and give you totally hot air), if the the valve is working properly. (And also save your climate control panel from blowing out the ground traces, if it shorts internally).

Here's the normal operation of the DCCV:

Center pin to the Dual Coolant Control Valve (DCCV) always has power (from the fuse box). The Climate Control Module (CCM) is active low, so it sends a Ground "signal" to the LH and/or RH pins on the DCCV to energize the respective solenoid inside the DCCV.

Normal Operation:

* Temperature setting "Lo" = CCM output ON (grounded) = solenoid ENERGZIED = solenoid valve CLOSED = coolant flow to heater core impeded = heater core NOT HOT.
* Temperature setting "Hi" = CCM output OFF (open circuit) = solenoid NOT ENERGIZED = solenoid valve OPEN = coolant flow to heater core allowed = heater core HOT when coolant is HOT.

Note: Even if the Climate Control System is turned off by the user, a functioning CCM will keep "CCM output ON" so that the cabin doesn't continue to heat up unnecessarily.

Apparently as the DCCV fails, the solenoids start to stick and not open all the way, and current draw goes WAY up, hence burning out the ground traces on the climate control panel. If you have a multimeter, you can check current draw of both solenoids. A good DCCV will show 1.0a or less...

You can Jumper both outside pins to chassis ground, and listen for the solenoids to click. Lastly another measurement, albeit a crude one, is to feel the output hoses to the heater cores - the metal ones with the quick disconnects. They shouldn't be "HOT" with the a/c on blast.

George

 

George,

Thanks for the detailed information. Unfortunately, I don't have the testing equipment you mentioned. I really question whether I can get to the DCCV's electrical connector with that valve bolted in place. Remember, I have huge hands and it's tough enough for me to get down there below the DCCV just to wipe it with a napkin checking for coolant leaks!

Feeling the metal output hoses leading into the heater cores is a good idea, though. So with the A/C on maximum cooling, they shouldn't be hot to the touch, huh? If they are, I assume that my DCCV is faulty and that is indeed causing my A/C problem. Agreed?

Still looks like rockauto.com may be the best source for a new DCCV. They show the Motorcraft YG378 part for $92.79 plus shipping. If I order it via UPS or FedEx Ground, total cost is $100.32. That's a great deal compared to any dealership I know of....

 

$100 - wow, wonder if they ship to here!!

edit: they do

 

Jon,

In theory when the A/C is on the dccv should suppress coolant flow to the outputs, and the heater cores. Can that be determined temp wise via the feeling output hoses, I'm not sure... BUT there should be some temp difference if a line has engine temp coolant flowing through it or not. Just be careful not to burn your huge hands in attempting to find out.

Now, As far as the electrical connection.

If you take the headlight shroud off, and look straight down between the coolant tank and the rad support, you will see the infamous 8mm bolt that holds the dccv to the rad support. if you have a LONG 1/4" extension hopefully with a magnetic pickup you can remove it pretty easily which gives you some ability to move the valve. Yeah rockauto seems to be the cheapest, although its $160 list at the ford dealer if you're in a bind. Dunno what the lead times from rock auto are.

George

 

Jon this is a long shot but look at page 3 posting #21 by forum member cleveland.
https://www.jaguarforums.com/forum/s...t=33822&page=4

 

George,

Thanks for the additional explanation. I felt those metal hoses yesterday just after ignition shut-off. The car had been idling for about 20 minutes with the A/C set on maximum cool. The metal hoses were not hot. I could easily hold them for long periods of time with my bare hands. So I assume the DCCV solenoids had been closed all through the idling time, preventing hot coolant from circulating to the heater core. In other words, my DCCV was (and is) working properly (as determined very unscientifically by the metal hoses not being hot). Agreed?



Rick,

Thanks for that tip. I had read that post just a couple of days ago and made a note to look for that sensor underneath the dash on the drivers side. Just haven't done it yet because like you said, I agree it's a longshot....



I'm still wondering about my condenser. I just don't have the A/C training or diagnostic tools to go much farther by myself. I still plan to call the body shop tomorrow morning when they open and say, "Guys - nice try but you didn't fix it. Now what?"

Any additional suggestions will be much appreciated. I don't want to go to the dealership except as a last resort. If the body shop can't isolate the issue, I may go to a long-time, well-respected automotive A/C shop that I know of from about 20 years ago. However, I expect them to say "Jaguar? Sorry, we don't work on those...."

 

Jon - it's a standard a/c system, no different to other cars and uses the same connectors ("quick release couplers" aka couplers). I use a set of gauges from the USA on my car and they fit perfectly LOL

Anyone who does a/c can check pressures, leak detect, etc. The shop that mended it should either do it themselves or have someone they call in (probably often). Guessing it may be the condenser is like guessing a rough engine may be the timing being out. Yeah, could be but you wouldn't guess.

 

I think it's a pretty unscientific, yet reasonably accurate way of ruling out the DCCV. A/C is A/C (as far as a 3rd party shop) no special fittings, just standard high and low pressure schrader valves etc..but they may not have the IDS system to tap into the sensors. The key here is a) what are the vent temps? Are all the vents the SAME temp? - Another issue may be vent flaps - the "warmer" air ones might be pumping in outside ventilation air, rather than cooled air. Then there is the inside temp sensor from that other post.

Personally if I were in your situation, I'd take it to the body shop, and put it on them, but give it a thorough test before you leave. If they can't make sense of it, they may have to sublet it to the dealer... I STILL don't think its a condenser issue. A condenser 90% of the time manifests itself as a hot at idle, cold at speed issue.

Let us know what happens,

George

 

George,

After reading the last sentence in your final paragraph above, here's what I did:

Cranked up the car with the A/C set on maximum cooling. Outside air temperature is about 88 degrees. Let the engine idle for 2 or 3 minutes while feeling the vents. Tepid, slightly cool air (the same as it's been for the past week or so) coming from all four of them.

Stepped on the accelerator and held the engine at about 2,500 rpms for at least 2 minutes. The air from the vents immediately got both stronger and colder, nearly to the point of what has been "normal" cold air from this car since we purchased it. Stayed that way for as long as I kept the engine at about 2,500 rpms. As soon as I took my foot off the accelerator and allowed the engine to return to idle, the vents blew that same tepid, slightly cool air again. Allowed it to idle for another minute, then shut the engine off.

So do these symptoms point to the condenser once again? Sure sounds that way after your brief explanation above. Keep in mind that my accident repair records show that the condenser was the only A/C part replaced by the body shop as a result of last year's front-end accident. They say they used a new, OEM one and I hope that's true. So maybe the replaced condenser has already gone bad. Either way, I'm calling the body shop in the morning to make arrangements to take the car back to them with my suspicions now focused on the condenser they installed....

 

By speed I reckon George meant moving along a road

It really isn't likely the condenser.

 

Jon,

Actually... No. That doesn't point towards the condenser. The condenser has an electric fan to cool it at idle. With a condenser problem, generally speaking its not engine speed that affects the temp of the air, but rather road speed, i.e. how much air is flowing through the condenser.

BUT... here's the good part. What you just described points to one of two things.

First, a slipping A/C or serp belt, or lack of proper tension... I'm not sure if the S-Type uses a separate A/C belt or has it on the serpentine belt. Think about it. The ONLY thing that changes with engine speed (with the car in park) is belt speed. If the belt is loose and slipping, you may not be spinning the compressor fast enough @ idle to generate enough pressure for proper cooling.

Second, is believe it or not, an undercharged system. Once again, same concept, lack of enough pressure to properly cool, at idle except in this scenario, the compressor spins fast enough to get "almost" cool air off idle, by increasing pressure. The compressor is basically a pressure multiplier. Takes the low side pressure and multiplies it by a factor, then into the condenser - raising the temperature and pressure there. The cooling effect is created by taking the high pressure gas, and suddenly dropping the pressure, so the temp goes down over the evaporator and you blow air over it into the cabin. The tell tale water drip from an a/c system is the condensation formed at the evaporator. Same thing as leaving a glass of ice water out on a hot day.

George

 

Yep, lack of charge is #1 by far. But it was filled after the repair (or should have been) so there must be a slight leak - but an actual leak not just seapage. One of the seals would be the most likely, I'd think, but basically they need to add UV dye (and a bit more gas) then if they can't find it immediately let you drive it for a while so when you take it in again they can finally find the leak by testing for the dye.

 

See... I tend to think it's not a SLOW leak... Two reasons...

First, if the car had a leak in the system, a proper A/C recovery machine would find it when it went to pull a vacuum and boil down the system. The system wouldn't hold a vacuum for the prescribed 30 mins. Plus the A/C would be ice cubes when it left the shop, and slowly deteriorate. A slow enough leak that it would actually hold a vacuum would not result in the A/C not working straight out of the shop.

I think either the car wasn't charged properly. Which makes no sense since it was supposedly on an A/C machine, and the proper charge label is right under the hood, OR the other scenario of belt slippage or a weak compressor comes into play.

George

 

I'm with you, except that you can get seals which do hold vacuum but annoyingly don't hold pressure. Not common, however. And also any of the various sensors etc could be to blame. Plus.... did the shop actually do it right?

Oh, and I may have missed it in the thread but was it icy cold when it came back from the repairer? And I do mean icy (as you know, but I'm thinking of others reading here).

I'd say: get it on a proper a/c machine. Do the proper cycle (empty, hold vacuum, check it stays a vacuum, refill (including dye), test center vent temperatures). See what happens. Quite cheap.

 

The car apparently came back from the body shop this week with the same mediocre A/C it went in with. I don't think it's a sensor issue per se. It might be a leaky seal as we suspect, but any seal that wont hold a proper charge for a day or two I highly doubt will hold vacuum.

MY Guess is an improper recharge. We've already established that the condenser was replace hence the system was opened due to the accident repair. Now Jon, Did you try the A/C at all last season? Or was this in the fall where the outside temps didn't reveal the problem? Maybe his machine is off in calibration and it's not adding the proper amount of refrigerant?? I wish you were closer so I could put my A/C gauges on it.

Jon if it were my car. Take it back, ask them to put it on the gauges as it sits. Look at high and low side pressures, both at idle, and with someone holding the motor at 2500 rpm. I bet they are on the low side at idle and get closer to normal at 2500 rpm... Then have them do a full cycle on the A/C machine. Pulling a proper vacuum, and recharging with the proper amount of r134 (by weight). Make sure they have the A/C on full blast when charging the system. If the system takes on the proper charge weight wise, and it's still doing what it's been doing, it's time to look at belt slippage, or the compressor.

George

 

Yeah, I'd go for that.

Make sure they do hold the vacuum for a long time (30 mins is good) because the system was open and needs to have the moisture extracted. Of course they should have done that already but maybe they didn't.

When they fixed it, they SHOULD have put on a new dryer. I never really believe that's needed in a repair like this BUT it does seem to be the recommended practice. And when repairing it must be only a small additional cost which sure removes the chance that the existing dryer will not recover when vacuumed. Jon - do you know if they did fit a new dryer? (Sometimes called a receiver or desiccator.)

Heck, for the quite small cost I'd be tempted to pay a different a/c shop to do the job (I mean checking/recharging), if need be.

If it goes back to the same shop, ask them for the low-side and high-side readings along the lines George says. Have a look at these sites if you want to get some ideas as to why:
www.aircondition.com/tech/questions/82/
www.aa1car.com/library/ac98.htm