Heater Control Valve?

[davemc]

Hello,

I am brand new to this site. I have a '95 SC400. Neither my heat nor air are working. I have heard conflicting ideas about this. One person told me that the Heater Control Valve affects the heat as well as the AC. Another told me that this is not true and that it only controls the heat. That being said, when I purchased the vehicle, the heater control valve had been bypassed with a piece of conduit. A friend of mine recommended that use a HCV from another vehicle to save money. So, I put in at HCV that fit and my heat stopped working. I don't know about the AC, because it was winter and I didn't try it. Today I had the AC tested and the mechanic told me my condenser isn't working. So my questions are:

1) Does the HCV have anything to do at all with the AC?

2) Do I need to purchase the correct HCV to get my heat to work again?

3) Should I take the HCV out and put the conduit back it? (my heat was working when it was not there)

Thank you!

[Tomj8]

Hello,

I am brand new to this site. I have a '95 SC400. Neither my heat nor air are working. I have heard conflicting ideas about this. One person told me that the Heater Control Valve affects the heat as well as the AC. Another told me that this is not true and that it only controls the heat. That being said, when I purchased the vehicle, the heater control valve had been bypassed with a piece of conduit. A friend of mine recommended that use a HCV from another vehicle to save money. So, I put in at HCV that fit and my heat stopped working. I don't know about the AC, because it was winter and I didn't try it. Today I had the AC tested and the mechanic told me my condenser isn't working. So my questions are:

1) Does the HCV have anything to do at all with the AC?

2) Do I need to purchase the correct HCV to get my heat to work again?

3) Should I take the HCV out and put the conduit back it? (my heat was working when it was not there)

Thank you!

[Tomj8]

Does A/C function normally? Can you rule out the Climate Control Module - do you have a display and can you control fan, etc? The climate control module controls the HCV and A/C thermostatically. If your CCM display is partially black or degraded, that could be an indication CCM is not working. Conduit in place of the HCV would effectively bypass the ability of the CCM to control the heat and would provide full heat all the time - does that sound like what's happening? If CCM isn't working, putting the HCV back under CCM control would effectively shut down the heat. CCM sounds like a suspect. Many postings on here have dealt with getting CCMs refurbished through Mikado Technologies in California - don't even think about buying one from a dealer. $$$$!!!!

[davemc]

Does A/C function normally? Can you rule out the Climate Control Module - do you have a display and can you control fan, etc? The climate control module controls the HCV and A/C thermostatically. If your CCM display is partially black or degraded, that could be an indication CCM is not working. Conduit in place of the HCV would effectively bypass the ability of the CCM to control the heat and would provide full heat all the time - does that sound like what's happening? If CCM isn't working, putting the HCV back under CCM control would effectively shut down the heat. CCM sounds like a suspect. Many postings on here have dealt with getting CCMs refurbished through Mikado Technologies in California - don't even think about buying one from a dealer. $$$$!!!!

Thank you Tomj8,

The AC does not work at all. By the CCM display, are you referring to where one reads the temperature, and climate control settings on the dashboard? That display is working fine. Also, the air blows forcefully, but the temp does not change. To answer your question, yes, when the conduit was in place the heat worked fine. However, I thought I should replace the HCV and used an ACDELCO replacement. I believe this is the part here: http://www.rockauto.com/catalog/raframecat...Rc1387032k84430

Now the heat does not work at all. In Chicago, we are going through a heat wave, so I am more worried about the AC, which does not work at all. If I put the conduit back in place, will the AC work?

[Psicks]

I had the same problem with the HCV on my '94, as far as I can tell it is only possible to reroute the vac lines to allow the heater to work properly I dont think there is anything you can do to allow the AC to function without replacing the whole part.

[davemc]

Thanks Psicks,

I replaced the part with the ACDelco replacement that was 20$, however the heat stopped working once I put the replacement valve in. Is this ACDelco valve no good? A mechanic today told me my AC compressor was shot, but could the bad Heater control valve cause him to mis diagnose?

Thanks guys.

[davemc]

Does A/C function normally? Can you rule out the Climate Control Module - do you have a display and can you control fan, etc? The climate control module controls the HCV and A/C thermostatically. If your CCM display is partially black or degraded, that could be an indication CCM is not working. Conduit in place of the HCV would effectively bypass the ability of the CCM to control the heat and would provide full heat all the time - does that sound like what's happening? If CCM isn't working, putting the HCV back under CCM control would effectively shut down the heat. CCM sounds like a suspect. Many postings on here have dealt with getting CCMs refurbished through Mikado Technologies in California - don't even think about buying one from a dealer. $$$$!!!!

Tomj8,

After I said the CCM works fine, I looked at it again. It is dark compared to everything else. It is not degraded, all the information can be read easily, but it is dimmer than the audio display. Is there a fuse that can solve this problem, or is the CCM shot?

Thanks.