Heater control valve delete turns cab into oven!

[SoloRiderForever]

I don't get it - I search all over this site and the cherokee site.  Everybody says to get rid of the heater control valve.  Well, I bought my truck with the HCV already gone - and my cab turns into an oven on a warm day and will totally bake you on a hot day.  I mean HOT!  Even with the windows open!

 

I've checked my blend door.  With the engine off you can hear the thing 'pop' shut.  It appears to me to work and be adjusted just fine.

But even with the AC on, which is capable of blowing cold, I get nothing but heat out from the heater box.

 

My heat/ac controls are from mid-90's and all work fine.  I'm considering putting a HCV back on, but since controls are different...   Which HCV (from '88 or mid-90's)?  I don't have the vacuum tank on the bumper anymore, so maybe an aftermarket cable-operated HCV?

 

It's truly too much to stand on a hot day - and those are coming!  Any suggestions?

 

(By the way - thank you to those that have created/maintained this site!)  

[eaglescout526]

Just put in a valve. Not sure why people say to delete them when they actually help keep cab temps down and help the AC power through keeping the tin can of a cab cool. 

[Minuit]

I found the heater control valve made a 3-5 degree difference in vent temps with an AC system in good working order - certainly not enough to blow hot air out of the vents even with the AC on, but enough for me to un-delete mine and install a Mopar valve. If you have blazing hot air even with the A/C (or regular vent) on, there's something else going on.

[jdog]

The ball is there to maintain vacuum for the hvac system, also when you say it makes noise, are you talking about a noise when you move the cable or just when you turn off the truck?

[scguy]

Sounds like you have a blend door problem

[cruiser54]

The heater door is controlled by a CABLE under the passenger side dash. Not by vacuum. That's where to look. 

[Parei_doll_ia]

Mine broke soon after I bought my truck. Put a ball valve in its place, open it when it's cold out and close it during the warm months.

[SoloRiderForever]

I know where the heater door is.  The 'noise' it makes is just the sound of the door itself closing - which I can see and feel as I'm dialing the heater control from heat to cold.  

 

Simply put, on a 90 degree day, deleting the HCV totally 'deletes' my AC to the extent that it's actually hot air that comes out the vents.  After a couple of hours of riding, I've touched all wheels, yokes, trans, xfer,... nothing else is overly hot.

 

My question is, will mid-90's dashboard controls work with an '88 heater control valve?  I must have vacuum as I have AC, so I'm going to have to find where that vacuum lines is 'pinched' off, right?  I know this is pretty basic, but I'm just a Gomer with tools that hasn't had this dash off yet.

[scguy]

If your heater door isn't broken, the foam seal must be gone, my Comanche on 100+ degree high humidity days cools just fine with no heater valve. Matter of fact, the heater valve is only active in the Max A/C setting. 

 

On full cold, there should be no airflow across the heater core. 

[scguy]

And as far as the heater control valve, any control head that provides a vacuum on MAX AC will work to control it. 

[cruiser54]

The cable operated heater door has to have something wrong with it. Rodents gotten in there? Made a nest? 

[SoloRiderForever]

cruiser54 - Rodents?  I was almost offended!  So, there is now a profile picture!  (I have problems uploading foto's - I make it tiny and it still asks me to crop it).

scguy - I'm a Gomer, but not that much of a Gomer!  I used to keep those old boxy '80's Volvo's on the road (mechanical fuel injection as opposed to electric), and I'm happy                  to rebuild and wrench on my old Harley's, but this is my first Jeep. 

              Blend door?  You can see it and touch it.  All is good with the blend door, even the foam.  Even Gomer could tell you - the blend door is fine.

              But what you said about the vacuum control head - That's the kind of info I need!  But 'm not sure what I'm looking for.  Can you elaborated please?  Would there be                  a nipple with a bolt in it (since it wasn't used)?  I don't even know what it would look like.

keeponjeepin - thanx!  But that doesn't work well in Colorado.  Our temperatures fluctuate by 40 degrees or more, every day.  It's nice to not have to open the hood to turn                    on heat.  Or did you put the ball valve in your cab?!?

Others - I'm glad your heater/AC works well with no HeaterControlValve - mine doesn't.  If you can help, I would be appreciative.

 

It's a build.  Overall, whoever did it (in Alabama) they did a good job.  I've got the new wiring harness, insulation glued to floors, donated interior, donated engine, I can't tell the lift but it rubs early in the turns.  It's been gone thru.  When I say good, the paint is beautiful, but they didn't let it dry enough before putting things back together - things like that.  But they still did a very good job overall - people on the sidewalks take pics of my truck as I'm driving by.  It's a beautiful truck - almost show worthy.

 

BUT, the HVAC and cooling systems have been a bit FrankenJeep'd.  From what I can tell, I have an Open/Closed cooling system - a radiator with a cap and an overflow bottle with no return line.  And it had no power to the aux fan when I got it - the thing on the bumper to turn it on is gone, so for now, I've 'borrowed' the foglight switch to power the fan.  I bought it in August, so I got about 1 month of high temps while driving it.  It seemed to me then that the truck is hot all around the front of the vehicle, but my temp guage appears to work fine and I haven't overheated.  It's been great all winter - but I never have to turn the heat on, just turn the fan up.

 

The truck is an '88, Engine: '91, Interior: '96ish.  Is there a reason - something not fitting from year to year, they changed the heater box in some year - something like that, that would have given the builder a problem when they built it?  If it's 95 degrees outside and I drive for 20 min with windows up and AC on, then it's 105 inside the cab.  Getting the hot water out of the heater core (by adding HCV) seems like a good place to start, right?

 

Now about that 'Vacuum Control Head' as scguy called it, any clue where I might find one?  It should be a nipple, right?  Size?  What's it look like?  I can't find it in my Hayne's manual and I've looked for what I've guessed it might look like.  This is where I'm clueless - If I get this info I'll have the HCV in the day after I get it! 

[watchamakalit]

5 minutes ago, SoloRiderForever said:

cruiser54 - Rodents?  I was almost offended!  So, there is now a profile picture! 

[cruiser54]

Perhaps there's an opening elsewhere in the plastic housing? 

[SoloRiderForever]

That, cruiser54, I don't know.  Havn't had the dash off yet and not looking forward to it.

 

Do you have any more info on that Vacuum Head that you were talking about?

[scguy]

The control head I was referring to is the AC control panel. It has a vacuum source line from the vacuum canister under the hood, and in the Max A/C setting, send vacuum back out to the heater control valve. If your different modes work (defrost/vent/floor) then you have vacuum to the control head. 

[scguy]

Maybe try just pinching a heater hose and driving it to make sure that the cab doesn't get hot. 

 

My 89 has no heater control valve and it blows plenty cold. 

 

Also, just making sure you're looking at the correct door. Does it have a cable actuating it for sure? Is it possible you're looking at the air inlet door under the blower motor? That is moved by a vacuum actuator?

[SoloRiderForever]

MJGomer strikes again!

 

First off, thanx to all that replied.  To all of you that said, "Hey, Gomer, it's yer blend door", you were right!  

 

But one of the members here, GJeep, had contacted me about another issue.  And he dogged me!  "It's the blend door he kept saying."  And I kept giving my Gomer responses.  Well, it was cool here this morning and I got impatient waiting for thermostat to open so I took it for a ride.  I got the AC blasting and I'm headed for several miles of uphill driving.  And the damn AC stayed on and cool and the cab was cool the whole way!!!  WTF!  Well, I finally got it to fail again and found that the cable screw needed tightening - that was it!  

 

(My apologies to anyone reading this that might be named Gomer)

 

Thread closed!

[Gjeep]

All good, any time! 

 

[scguy]

Awesome, great to hear

[cruiser54]

and the crowd cheers!!!!

[Eagle]

On 3/28/2022 at 6:36 PM, eaglescout526 said:

Just put in a valve. Not sure why people say to delete them when they actually help keep cab temps down and help the AC power through keeping the tin can of a cab cool. 

 

Jeep deleted the valve on the newer model XJs because with the flow of coolant shut off, the heater core tends to get clogged with gunk. But there's no reason you can't run a valve and just remind yourself to blast the heat for a few minutes once a month or so -- or manually reverse flush the heater core once a year.

[SoloRiderForever]

1 hour ago, Eagle said:

 

Jeep deleted the valve on the newer model XJs because with the flow of coolant shut off, the heater core tends to get clogged with gunk. But there's no reason you can't run a valve and just remind yourself to blast the heat for a few minutes once a month or so -- or manually reverse flush the heater core once a year.

Thanx Eagle.  Replacing heater cores is usually a pain, but in talking with Gjeep it sounds like these have a little extra pain to them.  Fortunately with the temp swings in Colorado you usually use the heat and air if you simply drive day and night.

 

All you guys give awsome advice.  On cars/trucks I'm mostly a decent part-swapper that's willing to make mods and customize and fabricate, but mostly a part swapper.  I've gotten about 3 pages thru one of Gjeep's builds and it's like art.  I suspect most of the people in this forum strive to be similar.  Simply put, you have to know how much guys like me appreciate guys like you!  Thank you.  And I hope to thank you more in the future!

 

PS - In my own defense, I suspect that this cable that was sometimes slipping on me is a 'fix'.  The stock cable must be a stock length, right?  My has a screw 'tightener' on the cable end.  That can't be stock!  (MJGomer Defense 101).

[Eagle]

13 hours ago, SoloRiderForever said:

Thanx Eagle.  Replacing heater cores is usually a pain, but in talking with Gjeep it sounds like these have a little extra pain to them.  Fortunately with the temp swings in Colorado you usually use the heat and air if you simply drive day and night.

 

 

Back in analog days (the 1960s and 1970s), AMC cars had a heater control valve that was operated by a simple choke-type cable by a lever on the dashboard. There were two versions: one had the inlet screwed into a threaded port on the head and a hose connection on the outlet; the other mounted to the firewall and had hose connections for both inlet and outlet. They were simple, and they worked.

 

I often wonder if all the fancy control gizmos we see on modern vehicles are really better than the simple, analog controls we had when I was learning how to drive and to wrench.

 

http://www.americanpartsdepot.net/images/130 3501H.JPG

[gogmorgo]

14 hours ago, SoloRiderForever said:

 

PS - In my own defense, I suspect that this cable that was sometimes slipping on me is a 'fix'.  The stock cable must be a stock length, right?  My has a screw 'tightener' on the cable end.  That can't be stock!  (MJGomer Defense 101).

Nah, the factory connection there is a bit jank. It's not at all uncommon for them to loosen or fall apart, whether by a passenger kicking it by mistake or what I don't think anyone's figured out, but it's a thing that happens.