AC blowing hot, DCCV replaced 2 times

[donmcgowen]

Hi,
I have done a lot of research on my problem but I'm yet to find a solution. Here is the deal. In the Winter, my heat blow cold, not ac cold, when at a stop light. When I accelerate, it will blow hot. When I use my AC, I get the exact same thing. When accelerating, it blows hot. I have changed the DCCV 2 times, flushed the coolant, and change the upper rad hose with new thermostat.
After some tests, I have determined that the dccv is not being activated so it is not closing off the coolant from the heater core. Also, I tested for 12V power to the DCCV, and it does get power. What controls the DCCV? I'm thinking of replacing the DATC, but I would like to know what controls the DCCV. Also, this does not explain the heat only blowing hot when accelerating. It seems as if the DCCV is stuck open, but again, why is it not hot when stopped. And, why is it not being closed when the AC is turned on?
I'm almost going to take it to the dealer, but I've never taken a car in to be fixed before. I can't take another summer with no AC, or a winter where I don't have heat when I am stopped.

 

[joegr]

The DATC controls the DCCV. If you have a V8, the DATC also controls the aux pump. If the aux pump is failed (or not being turned on by the DATC) then you won't get much heat at idle.

 

[donmcgowen]

I have a V6,

Hi,
I should have mentioned that I have the V6, so I don't have the auxiliary pump. What I"m trying to determine is if maybe the datc is not grounding the dccv. The DATC is not giving any error codes.

 

[oddball]

At this point, I think you'd have to check the wiring and what signals the DCCV is receiving since you've already replaced it twice.
It may be a DATC problem, it may be a wiring problem.

Also, just to check, make sure the fuse for the DCCV is good. The valves are normally open, and require the solenoids to be powered to close.

 

[LLCoolLS]

I have the same/similar problem.

At idle, with the DATC set to full heat, not much heat is coming out. Air gets hotter as I accelerate. Also, now that the weather is warm, I use the AC, but I can feel both cold and hot air mixing in the center panel vents. the driver side vents is just luke warm.

I just changed the DCCV but that changed nothing.

I did make sure I bled the system properly. I get no trouble codes using the off/floor test or the off/panel test. The AC compressor clutch is staying engaged.

With the AC on full, the passenger air is cool, but not cold. Only about 70 degrees F. The driver side is blowing about 95 F.

On full heat (@ 2000 RPM engine speed), the passenger is blowing 125 F, and the driver side is blowing around 120 F. I'm thinking it's the DATC, but I'm not sure enough to fork out the cash. The one comment about the auxilliary pump makes sense for my heating problem, but not for my cooling problem. It feels like the DCCV is staying open, but I just installed a new one yesterday with no change.

BTW I have a V8.

Any reinforcing thoughts?

 

[TooManyToys]

Wrong post ....

 

[donmcgowen]

Help testing DCCV

Hi,
After replacing the DCCV twice but it still doesn't work, I would really like
some help testing it. The DCCV does have 12V power, but it is still not closing
when the AC is turned on. How can I test that the DATC is sending the correct
signal to the DCCV to close when the AC is turned on. I'm going to just replace
the DATC since that is the only thing left that has not been replaced. When I turn
on the AC and let the car get hot, I check the hoses going into the firewall, and
all 3 are hot, meaning the DCCV is not closing to prevent coolant from flowing
though.
Any help would be appreciated. I have fixed every problem with this car
except this, and I'm not going another summer without AC. I'll give it another
month, then I'll just suck it up and take it to the dealer if can't figure out why the
DCCV is not working correctly.
Please, if you have any ideas they would be greatly appreciated.

 

[joegr]

Most of the time, it is the DCCV. This time it isn't.
It could be the wiring to the DCCV, the DATC, or the temperature sensors read by the DATC. I've seen or heard of the DATC causing this, and of the evaporator temperature sensors causing this. If you have a good scan tool with live sensor readings, you can call up the evaporator temperature sensors and see if their readings are sane. You'd also want to look at the in-car air temperature sensor and the exterior temperature sensor. The exterior sensor is easy, since you can display its reading on the DATC.
I assume you have done the DATC self-diagnostics?
I have procedures to test the wiring, but I don't know what year your LS is.

 

[donmcgowen]

my car is a 2000 LS V6. I think what you were saying joegr is on the right track.
I know the DCCV uses 12v power and when the AC is turned on, it should send power to the valves to close them. I'm just not sure how to test for it with the voltmeter. Also, I have checked for codes on the DATC and it shows none. As for the evaporator temperature sensors, I have no idea how to test those since I do not really have much testing equipment. But I think you are on the right track. It figures i would get the most difficult abnormal problem. It couldn't just be the DCCV.

 

[joegr]

Gen I DCCV wiring tests

.

 

[donmcgowen]

Problem solved

So after pulling most of my hair out, I now have AC. After all the trouble, it was
the DATC. I had replaced the DCCV twice, vacuumed and recharged the 134a refrigerant, and replaced the drier. I was at my wits end since nobody seems to
have my problem. So I picked up a DATC from ebay for $70. I put it in yesterday and voila. Cold air. I can't believe it. Thanks for everybody's help getting the testing instructions.