I have been fighting with my heater and a/c. I had replaced the climate control module and the a/c began working but the heat was not working. I had the heater valve replaced and found the antifreeze had turned to gel from improper mixing (see picture). This prompted a system flush. Now the heater works great but the a/c does not work now. The mechanic says that he only unplugged the heater valve, coolant reservoir jug, and plugged both back in and suspects the heater core is clogged up causing the a/c not to work. I checked the freon and it is full and the compressor turns on properly. Can anyone give me ideas of how to fix this?

 

My suspicion is that your bad DCCV has ruined your replacement control module. A bit of time with the search function and you'll find a step-by-step troubleshooting guide. Either you misunderstood your mechanic, or he just put down the crack-pipe. No amount of heater core clogging, whether air-side or coolant-circuit could be responsible inoperative a/c.
Sounds like your DCCV is open when it should be closed. Since it is new (bear in mind we've had numerous reports of them being bad out of the box) we'll give it the benefit of the doubt: Unplugged? It needs power to close, so check the plug, check the fuse. Next up would be to determine if the control module is commmanding it open due to some failure?

 

Thanks for the info! I doubt that the bad DCCV ruined the control module only because it worked when I dropped the car at the shop and it did not work when I picked it up. I am hoping that it is just unplugged or maybe a fuse. I'll start there. Thanks a bunch for the input. I was wanting to verify my thoughts about the mechanic...

 

But when you dropped the car at the shop, your DCCV was fully clogged and passing no coolant to the heater core, at least from the look of the picture. Now, you have a new, ostensibly fully-functional DCCV. So quite possibly you have a trace burned out on the control module board because it spent itself trying to close the old valve through all the gunk. Now it can't close it because there is no longer a circuit there.......makes perfect sense after you've performed the repair on a climate control module. But I'll hold out hope that he either failed to plug the valve in or that you've got a blown fuse! CCM repair isn't hard, but those other two are surely easier.

 

I'm not sure I fully agree with this theory, with all due respect. (I mean that in the truest sense, not the Ricky Bobby sense...) The DCCV solenoids can operate at 100% duty cycle fully closed when no heat is required. Even if stuck due to debris in the valve body, it shouldn't hurt anything if the controller is sending a constant close command. There's no position feedback from the valves, either, so it's not like the controller can increase the current flow. Now if one or both valve solenoids had an internal short, that would increase the current flow and potentially damage the controller, but the simple presence of debris shouldn't cause an electrical overload. A solenoid will draw the same amount of current, whether the core moves or not.

I suppose the big question is how was the AC before the DCCV was replaced?

Are the AC lines getting cold? That would help determine if the AC system was actually cooling. Put your hand on the AC thermal expansion valve. This is located on the front centet of the firewall, directly behind the engine. It should be nice and chilly.

If the AC lines are cold, my hunch is some debris was still trapped in the coolant lines and it migrated into the DCCV, jamming the valves open but not stopping all flow. The AC system is trying to cool, but is overwhelmed by hot coolant still reaching the heater core. That's my story and I'm sticking to it.

 

You called the fried module. Argh. I can fix it. Hopefully that will be the final fix!

 

The a/c was working great before I took it into the shop. I didn't check the lines before I took the module out. It'll probably be best to flush the lines out again before I reconnect the control module, argh. I imagine it could cause the same problem if I don't...

 

I agree wholeheartedly with Karl's description of system operation and his theory of why the DCCV being stuck can't damage the board. On the other hand, scratch a stuck-closed DCCV, and you'll likely uncover a knackered climate control module. Put another way, replace your DCCV due to lack of heat, and more often than not, you'll find the nice, cold a/c has taken leave of the premises. As mentioned above, an easy, free test of notional a/c circuit performance is grabbing the suction line. If it's nice and cold, you are most likely looking at hot coolant in the heater core when it isn't supposed to be.
(Be careful you don't get the discharge or liquid line by mistake...they'll be quite hot if it is operating properly)
The electrical engineer, try as he might to do otherwise.....is forced to live in an analog world. BTW, Caveforce, great pics of the board!

 

Thanks for the pointers! I'll definitely be careful when I check the DCCV. I'll be fixing the module tonight. Wish me luck!

 

Check fuse R1 in engine bay and relay. If that checks out your new heater valve is bad out of the box. Happens more often than not, unfortunately. Or some of your coolant sludge made it to the DCCV again.

 

Didn't you see his board pics? Yeah, all things are possible, including a blown fuse AND a bad valve......but he definitely has a board problem. I doubt that climate module is going to close a good valve even with an intact fuse until he repairs it.

 

Yes, I saw it after I posted. These are still steps the OP will need to check after fixing the broken trace on the board.

 

The reason the modules get burned is once the DCCV solenoids start sticking they start drawing more and more current. The module was designed wrong and has no protection so when this happens either the fuse blows if you are lucky or the module burns out.

The module re-builders even offer an added service that installs some current limiting into the circuit so when the DCCV starts acting up it can't draw enough current to burn the module out.

We have had the repair and protection options (Several ways to provide the protection. Even a simple in-line fuse will work.) fully documented on this forum. So other than just repairing the burnt trace you can also stop it from happening again if you want.

The real solution is to NOT let a bad DCCV linger. The longer you run it bad the more likely you will burn the module. Not guaranteed as it seems to vary. Sometimes the module goes right away but we have had people run bad DCCV's for a long time with no module damage.

I was lucky as I knew about the DCCV problem because I came from a Lincoln LS. So I replaced it on my 2005 STR when I first saw some red stains on the DCCV.
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