Adjusting water valve to maximize A/C performance (1 Viewer)

[cartercd]

Here is a fix that might lower your A/C vent temperatures.

When you slide the temperature control selector on the dash between hot and cold, it opens/closes the hot water valve. When the temperature selector is at the full cold position, the hot water valve should be closed. In my case the valve was still partially open, which introduced hot water into the heater core. After making an easy adjustment to the control cable, I saw my vent temperatures drop 2-3 degrees, which was welcome in 110 degree Phoenix heat. I've seen other posts on this issue, so I suspect others might have this problem as well.

The hot water valve is mounted dead center on the firewall with heater hoses coming off each side. You can easily see how the control cable pushes/pulls on the valve handle to close/open it. With the engine running and the temperature control selector on full cold, make sure the valve handle bottoms out against the stop. If there is any gap, you need to loosen the cable housing clamp and re-position the cable until the valve closes completely. The drawings below should clarify how it all works.

 

[alaskacruiser]

I recall prior threads mentioning this phenomenon, but no fix. What a simple fix! I will give this a shot once I get my rig back. Great work, man!

 

[OGBeno]

I recall prior threads mentioning this phenomenon, but no fix. What a simple fix! I will give this a shot once I get my rig back. Great work, man!

Agreed. Good job on this. This should be added to the FAQ section.

-o-

 

[Trunk Monkey]

One of my friends just unhooks the valve in the summer months, been working great for me so far this summer.

 

[murf]

Thanks to a fellow valley dweller - esp. since this is a record year with days over 110 degrees. 21 or 22 and counting....well take every degree we can take. i'm also looking into the JDM electric bolt up pusher fan for extra flow during slow wheeling/ slow traffic/ stop and go. ( A auxillary fan for Aussie 80's built with dual A/C im told) This will help those moments when its so hot the ac loses efficency and gets luke cold. Do a search on JDM electric fan and look for the Cdan thread....worth the look!

 

[KliersLC]

One of my friends just unhooks the valve in the summer months, been working great for me so far this summer.

I'd advise against this just because of the oft chance that you have some sort of cooling system failure (fan clutch, radiator, cap, etc) you can use the heater to cool the engine down some......

 

[Red Beard]

I'd advise against this just because of the oft chance that you have some sort of cooling system failure (fan clutch, radiator, cap, etc) you can use the heater to cool the engine down some......

Just going to say that. Definitely. I just had to do that. Thermostat broke, so I was driving with my windows open and my heat on at full.

 

[airlaird]

Your'e a genious

In all of my searches and posts about my lousy A/C, I have NEVER heard or read about this being a possible remedy. After trying everything in the last year I came upon carter's post...thankyou for the post!
I have submitted a pic of my cable and it is 1/4 inch away for the stop!!!!! So, I need to adjust the cable.
So, do I simply "pull" the cable toward me as it sits in the "cradle" or support bracket??
airlaird

 

[cartercd]

Yes - the cable housing needs to be a pulled toward you a bit. It takes some trial and error to get it just right. Ideally you want to get it so:

- at full cold position on the temperature selector the valve is closed
- at "almost" full cold position the valve is slightly open

This will give you a nice linear relationship between the temperature selector position and the valve position. At first I adjusted the cable too far, and the valve was closed at the full cold position and it was still closed when I moved the temperature selector over an inch.

Let us know the before and after results.

 

[IdahoDoug]

I took a look at the water valve innards through the end tube of my 97 once. I recall that even at full shut according to the outer lever position there was a small gap still allowing some movement through the heater core to prevent corrosion or deposits. Agree the valve shut is best, but wanted to provide this data. It's a white plastic valve and acts with the hole shutting down to a small slit. You can see it if you remove the hose on the end pointing toward the brake fluid reservoir.

DougM

 

[airlaird]

It worked!

Well, after putting more R134, Installation of a GM fan blower, wrapping the A/C tubing, new valve, Drilling 4" holes in the hood for venting hot air, mounting an aux fan hood, installing limousine tint, installing an auxilliary pusher fan, and blue fan clutch mod......this worked!!
My A/C (read my previous thread above) is now C-O-L-D.
After three years...this mod which I have never heard of did the trick.
My thanks to Carter and to Landtank with his Blue clutch mod which helped...
I feel younger and I think my hair is thicker now )
airlaird

 

[Trunk Monkey]

I'd advise against this just because of the oft chance that you have some sort of cooling system failure (fan clutch, radiator, cap, etc) you can use the heater to cool the engine down some......

Takes 5 seconds to hook it back up.

 

[alaskacruiser]

Well, after...mounting an aux fan hood
airlaird

airlaird- what is this?

 

[fatfish]

Went out and checked mine , and after a little adjusting you can feel that the air is cooler. I also found a loose vac hose under the intake plugged it back on and my rig runs much better, This was been a win/win kind of day.

 

[KliersLC]

Takes 5 seconds to hook it back up.

The time it takes you to pull off the road on a long hill, open the hood, get out, burn yourself on hot engine bits, hook it up hose and get rolling again would cause a significant temp spike in an already overheating engine. Might be the difference between driving home and getting towed.......

 

[airlaird]

Typo

airlaird- what is this?

Sorry, that was a typo...and a duplication, meaning I installed an aux pusher fan..
airlaird

 

[cartercd]

I recall that even at full shut according to the outer lever position there was a small gap still allowing some movement through the heater core to prevent corrosion or deposits.

Do you think this is a common practice in OEM design? In addition to the corrosion/deposit issue, could it also be to prevent thermal shock to the heater core?

I would be interested in trying to modify the valve (perhaps by adjusting the position of the stop) so it closes fully if I thought it wasn't going to do anything detrimental to the heater core. I'm reluctant to mess with Mr. T's design, but in this heat I'll contemplate it.

 

[IdahoDoug]

I just want to clarify - go ahead and adjust yours so the outer lever is against the stop metal thing the diagram shows. No worry with that, just wanted to say that there is still some flow and it's likely for the health of the heater system as a minimum movement that I would not suggest reducing further by pinching off hoses, etc.

DougM

 

[Romer]

Great thread, I'll add it to the FAQ later tonight or tomorrow.

 

[mason]

Thanks for posting this. I checked mine, and it was at full stop. AC has been great, but this gives me peace of mind!

-Eddie