Dual climate control blowing heat on AC (DCCV removal instructions in post #107)

[shorod]

Is it Hot regardless of the set temperature? If you set the temp to 60 degrees, is it still coming out the vents hot? The DCCV is the Dual Coolant Control Valve. It regulates the amount of coolant flow for the driver's and passengers heater cores. If the DCCV is working properly, it should be shutting off coolant flow through both of the cores when the set point is 60 degrees. However, if one or both of the valves are stuck open, or there is a short causing the valves to remain open, you will get constant coolant flow through the cores which will probably overpower the evaporator core chilled/dehumidified air and feel hot at the vents.

If at 60 degrees setpoint the air is cold, then you probably have a sensor issue somewhere.

-Rod

[2005LSdude]

Originally Posted by shorod

Is it Hot regardless of the set temperature? If you set the temp to 60 degrees, is it still coming out the vents hot? The DCCV is the Dual Coolant Control Valve. It regulates the amount of coolant flow for the driver's and passengers heater cores. If the DCCV is working properly, it should be shutting off coolant flow through both of the cores when the set point is 60 degrees. However, if one or both of the valves are stuck open, or there is a short causing the valves to remain open, you will get constant coolant flow through the cores which will probably overpower the evaporator core chilled/dehumidified air and feel hot at the vents.

If at 60 degrees setpoint the air is cold, then you probably have a sensor issue somewhere.

-Rod

Just now able to get back with you Rod. No it's Hot no matter what no cold period, run it down to 60 and still Heater HOT both sides. Even if dual is selected or not. So it DOES sound like the DCCV? Right? thanx again...

[shorod]

Yep, it sounds like the DCCV may be stuck open. One additional test would be to unplug the DCCV electrical connector and see if you still get heat. If so, that would indicate the DCCV is stuck open as I believe the DCCV is supposed to open with battery voltage applied. If you remove the battery voltage and the flow of coolant is still to the heater cores, the DCCV is not closing.

I'll have to confirm that the DCCV opens with battery voltage....

-Rod

[2005LSdude]

Originally Posted by shorod

Yep, it sounds like the DCCV may be stuck open. One additional test would be to unplug the DCCV electrical connector and see if you still get heat. If so, that would indicate the DCCV is stuck open as I believe the DCCV is supposed to open with battery voltage applied. If you remove the battery voltage and the flow of coolant is still to the heater cores, the DCCV is not closing.

I'll have to confirm that the DCCV opens with battery voltage....

-Rod

Great, now it sounds like where getting somewhere. so you probably already know I'm going to ask where the DCCV electrical connector is located?, I Don't have CD manual or regular manual.. thanx Rod.

[shorod]

The DCCV electrical connector on the 2002 is located to the left side (as you're standing in front of the car/engine compartment) of the radiator towards the top of the radiator. You can follow the wires down to the DCCV connector which is about 12 inches of wire away. I suspect the 2005 model year is similar. There are three wires in the connector, a brown/green, red/orange, and black/orange.

And from my quick look through the service manual, it does appear that battery voltage opens the solenoids, so unplugging the DCCV should stop the flow of coolant to the heater cores if the DCCV is working.

-Rod

[2005LSdude]

OK, great I'll check that and let you know soon. thanx again Rod.

[BeePee60]

Thanks for all the good info in this thread. I have a '95 Town Car without dual zone climate control, and it also blows hot air and cold simultaneously when the A/C is running. Just got done replacing the blend door actuator on the advice of a mechanic at the local dealership (what a pain), but that did not solve the problem.

The self-test of the ventilation system control module yielded the codes 0115 and 0125. Do you know the descriptions for these? Thanks much in advance.

[shorod]

Welcome to the forum!

The code 115 is for "Intermittant engine coolant temperature signal" and code 125 is "Intermittant vehicle speed signal."

If you haven't already, you should consider checking the Town Car forum for common issues that may cause these codes. You should also check the PCM diagnostic codes and see if these codes are mirrored there. That may help you determine if the issue is likely with the sensors or with the wires/connections for the EATC system.

-Rod

[BeePee60]

Thanks for the codes - I thought they might be specific to the heating and A/C system since they came up there on the temperature display after running the self-diagnostic and did not appear when I checked the OBD II codes with a code scanner.

What else would cause the A/C to blow the hot? The pipe from the compressor is cold to the touch and the compressor is engaging. I can hear what sounds like the blend door moving when I press the ventilation control buttons. When the car is first started cold, I have good A/c, but as soon as the engine warms up, the hot air overpowers the cold. Any further ideas would be appreciated. Thanks.

[shorod]

The heater control valve, if stuck open, will cause the symptoms you describe. Also, I found on my wife's LS that a bad AC Evaporator discharge temp sensor will cause heat at any set point other than 60 degrees F.

-Rod

[CabinFever]

New guy here. Read and followed procedures outlined. Still have hot air from passenger vents. Bad mixture door? Any help would be highly appreciated. Oh yeah, no error codes show up.

[CabinFever]

New guy here. Tried all the procedures on the DTC testing using the panel but recieved no trouble codes displayed. Hot air still present on passenger side. Disconnected the heater control valve but hot air still present. Is it the cause of the trouble?? Please help!!

[shorod]

With the DCCV disconnected, it should have allowed full coolant flow if working properly. When the valves receive battery voltage, they close.

Based on my experiences with my wife's DATC and a few others on this forum, I'd suggest switching around the Evaporator Core discharge temp sensor with the driver's side air discharge temp sensor. On the earlier LS, those two sensors are the same part number, along with the passenger side air discharge temperature sensor.

-Rod

[CabinFever]

Thanks for the info. I will try this out. These are on the air plenum under the dash? I think so, but not sure. I will let you know my results with this test.

Thanks Rod....

[shorod]

Yes, on the 2002 model year they are located on the center plenum, two on the driver's side and one on the passenger side.

-Rod