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Unread 05-20-2013, 02:54 AM   #1
hshark
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1996 XJ Cherokee 
 
Join Date: Mar 2013
Location: san diego, ca
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Help Me understand HCV

Ok so let me start by saying that I live in a part of California that is humid, hot, and dry. We get 105+ degree weather here with high humidity. Now with that said I've been reading a lot on the HCV that my new to me 96 XJ that was originally from Colorado does not have. So I have hot water running into the heater core while my A/C is on. I've read many post where people debate as to no significant difference in the A/C temps with the heater bypassed. However I've seen post that say A/C temps seem better with the heater bypassed. Note I used the word "seem" as no objective evidence has been presented. So has anyone out there bypassed the heater using the HCV and achieved better A/C cooling? I just had my A/C serviced do to PO replacing compressor and everything is working fine gauges read good (per a/c tech) clutch cycles fine, liquid line is cold other line is hot etc. So I feel its logical to contend that if my A/C is running in extreme weather i.e. 105+ high humidity and then I have the good old heater core pumping hot water through it that this will have its effects on my A/C cooling efficiency. So I'm willing to do the install and it seems fairly easy, but my concern is with what seems to be the vacuum hose on the HCV. Where does this go to? Does it even have a vacuum hose? I don't have the part, but it seems from pictures that it has vacuum. Also my blend door is closed while on Max A/C. Any thought, suggestion, stories etc.

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Unread 05-20-2013, 01:09 PM   #2
Max78
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1992 XJ Cherokee 
 
Join Date: Jun 2009
Location: Tucson,AZ
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This should be the same as yours.

My AC system would always blow through the heater core for at least 30 seconds before the door would shut and it would bypass the heater core. Even then it still leaks by that door as the seal is old and crappy. My heater core valve was stuck open all the time too. So I zip tied the heater core valve closed and the blend door to always bypass the heater core.

I noticed on start up it would get cooler MUCH faster, and if I went into a store and came back out in 5 minutes I would not be blasted with a heat gun for 30 seconds. Closing that door also gave me allot more airflow through the vents as well. We have been in the mid 90° temps here and the AC in this jeep will actually make you uncomfortably cold, and I have zero window tinting.


Max AC will recurculate the air in the cab, Normal will draw in fresh air, those are the only differences.


I would bypass it till winter, or put a valve in there. Yes it runs off of vacuum, No vacuum its open, vacuum applied and it closes. You can T it into any of the vacuum lines coming out by the throttle body.


If you really want I can run a test with the heater core flowing and blocked off.


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Unread 05-20-2013, 01:22 PM   #3
fishtaconc
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2004 WJ 
 
Join Date: Feb 2009
Location: Watha,NC
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As Max78 stated if the seal around the blend door is failing it could cause them to fight one another. At the same time Jeep did away with them (HCV) on the later 96s through the end of production. Personally I wouldn't be concerned about it, as they are just another failure point in the cooling system, if you do feel that it is affecting your A/C performance, you can always install a boiler valve, its brass so it wont get brittle and break like the plastice HCVs. just my $.02
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Unread 05-21-2013, 09:16 AM   #4
hshark
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"So I zip tied the heater core valve closed and the blend door to always bypass the heater core. "

So it seems like I overlooked my XJ it does have the HCV and it seems like its connected properly i.e. vacuum etc. Now my question is how do I know it's closed or bypassing the heater core? How do you get the blend door to always bypass the heater core? How can I do this which way should I crawl under the dash? See In the morning my A/C is nice and cool, but come 12pm it can't keep up. Thanks for the help...
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Unread 05-21-2013, 09:39 PM   #5
cruiser54
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I live in Arizona and have eliminated numerous HCVs with no ill effects. Make sure your blend air door is closing completely when the control is moved all the way to the left and you'll be fine.
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If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-21-2013, 10:57 PM   #6
hshark
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Ok so I see a pic of the ac unit stuff, but how should I go bout doing this i.e. blend door closing?
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Unread 05-22-2013, 06:00 AM   #7
cruiser54
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Blend door is under the passenger side dash. Poke your noggin under there. With your left hand, move the dash temp lever back and forth. It's moving the door up under the dash. Where the cable attaches to the lever under the dash, make sure the lever is going all the way back to it's stop when the lever on the dash is all the way to the left. If it isn't, the clip on the cable is easily adjusted.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-22-2013, 08:06 AM   #8
Max78
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I'm a sucker for zip ties. . . lol. Maybe I'll get under there and fix it correctly one of these days. . .

Just a note, my cable was loose and the blend door did not move when the temp selector was moved in either direction, yours might be connected correctly, just poke your head under there and look.

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Unread 05-22-2013, 04:17 PM   #9
hshark
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Ok I'll check today, thanks!
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Unread 05-22-2013, 04:58 PM   #10
cruiser54
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Quote:
Originally Posted by Max78 View Post
I'm a sucker for zip ties. . . lol. Maybe I'll get under there and fix it correctly one of these days. . .

Just a note, my cable was loose and the blend door did not move when the temp selector was moved in either direction, yours might be connected correctly, just poke your head under there and look.

I stole your photo...LOL.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-22-2013, 05:18 PM   #11
Max78
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Quote:
Originally Posted by cruiser54 View Post
I stole your photo...LOL.
Thats fine, making a redneck how to? Zip ties and stuff
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Unread 05-25-2013, 07:05 PM   #12
hshark
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The door was open just so you guys know. Thanks!
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Unread 05-25-2013, 07:43 PM   #13
cruiser54
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Quote:
Originally Posted by hshark View Post
The door was open just so you guys know. Thanks!
Thanks for the update. Appreciate it.
__________________
Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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