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

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Here is a :banana: 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.
View attachment 168598View attachment 168600
Can you please clarify or picture "the stop"
 
See red circle. The rotating arm of the valve should touch this at full cold setting.

Capture.JPG
 
Thanks cartercd! Just did this, took all of 5 minutes, now AC is throwing snowballs!
 
So I'm not getting any heat. I took the cable off and moved the valve all the way open and I'm still not getting any heat. A.c. works great. You think I can rule this out as my problem? Thanks.
 
So I'm not getting any heat. I took the cable off and moved the valve all the way open and I'm still not getting any heat. A.c. works great. You think I can rule this out as my problem? Thanks.
Your post contains insufficient information for the collective genius here on Mud to solve your problem from afar.
 
Your post contains insufficient information for the collective genius here on Mud to solve your problem from afar.

sorry. I was somewhere with very poor internet and only had my phone. I've read through the whole thread now. My question is this:

I'm only getting full blast A/C. I can move the temperature control lever in the cab all the way to the red and nothing happens. I would think that this means my servo motor is blocked (which is likely as the previous owner installed an aftermarket stereo before selling it to me). However, if I pop the hood, unhook the cable, and move the valve all the way open (all the way to the passenger, or "hot" side) I still don't have any heat in the cab. It's still blowing cold.

Do you think this means the valve doesn't open or is blocked and I need a new one?

Next question, I want to pull the valve to check it. Do I need to clamp the hoses on either side before doing so? Will coolant go everywhere if I unhook them?

thanks.
 
Valve fails because the plastic hose connections fail, it won't be blocked. Servo/electronics are not working as it controls cable and blend doors.
 
Valve fails because the plastic hose connections fail, it won't be blocked. Servo/electronics are not working as it controls cable and blend doors.

thanks! I took the dash off thinking the aftermarket stereo wiring was causing problems and turns out the guy that installed it decided not to plug back in any of the wiring harnesses for the rear heater or the temperature controls :slap:

working like a charm now!
 
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for those trying to solve this issue, I wanted to add:

if you have an aftermarket stereo installed, the new bundle of wires may be getting in the way of the cable servo motor movement.

with everything pulled out (stereo, ashtray, ac, hazard etc) I tested it and I found that it worked, where before the cable/valve at the firewall was not moving. I found a plug had gotten in the way of one of the tracks of the motor movement, blocking the cable from being pushed/pulled. cleared everything from around it (stuffed it up actually where there was some room) and it works as it should.

I wonder if I hadn't checked it, that after time something might eventually have broken around the control box.

The cable end loopside to the heater control valve is not moving switching the heater control slider from hot to cold and back again. I can see the servo pushing and pulling the other end of the cable. So the servo is working. I just can't see if the servo is getting its full range of motion. Maybe the cable is kinked up somewhere along the line but I doubt it.

Ill pull the dash to get at the stereo to see what going on behind the scenes.

For now, the heater control valve will be kept in the closed position as the cable loop end is disconnected from the valve.

Great post. Thanks.
 
thanks for this post. I installed new stereo and after that, my temp slider stopped working (cable not moving the valve).

I sprayed rust converter in the metal parts in the dash to stop rust while I had dash open. Some of spray got on the connectors so it may have fried at the plug for the servo. I have to look at it again and see where my problem is. I hope it's an easy fix.
 
Here is a :banana: 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.
View attachment 168598View attachment 168600
Awesome! I've been fighting with my AC system for years. I looked under the hood and yep, there was a gap. So I disconnected my control cable because it was not moving at all. Now its running a little cooler at idol. After a thousand plus $ and replacing the compressor, evaporator and condenser, it funny how all the AC techs that have serviced my rig never noticed the gap.
 
Troubleshooting an issue with this, but slightly different, in that I don’t care about AC.. just want adjustable temperature. The heat I do have is nice and hot, but it’s all or nothing. AC is disconnected. Cooling system is in great shape with recent thorough service.

Temp slider anywhere between cold and 85 makes no difference whatsoever (valve lever doesn’t move at all)... as soon as I push that last bit past 85, the cable pulls and opens the valve all the way. There is no in-between; it’s on or off.

Doesn’t matter if I’m all the way toward cold on the slider, since the cable stays put up to 85, BUT with it all the way to the left, I adjusted the the clip so the lever lightly touches the stop (had a small gap at first). Doesn’t really matter in my case, cable does the same thing, and I’m not trying to maximize AC anyway.. although “lowest temp” setting being a hair cooler wouldn’t hurt.

Read every post, and a couple other threads. I see a couple folks with the all-or-nothing cable issue, but not getting anything out of it for my case. Did I miss something? Servo something something? Trying to get cable to have a “linear relationship” with temperature slider.
 
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i just checked mine but couldn’t see it with my eyeballs so snapped a pic. looks like i’m off by a hair.

<edit: thought i adjusted it but it looks like it is in the same place. so was the word that the stop is sometimes off by a mm and a half or something due to the internals? or i should be able to snug it up against the stop?>

A91A9A09-B411-4910-B295-BED4A53E6072.jpeg
 
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i just checked mine but couldn’t see it with my eyeballs so snapped a pic. looks like i’m off by a hair.

<edit: thought i adjusted it but it looks like it is in the same place. so was the word that the stop is sometimes off by a mm and a half or something due to the internals? or i should be able to snug it up against the stop?>

View attachment 2436516

Mine looks the same as yours. New HCV, adjusted the cable too, and it's always off by about this much when I used the cabin lever. But under the hood I can use my finger to push the valve to the stop. So maybe just a little more adjusting needed, I'm going to try but it's not at the top of my priority list right now.
 
Sorry to revist the dead thread, but is there anything else that needs to be adjusted to get heat? The slider in the climate control unit does nothing and I am not sure where the break is. All other functions of climate control work.

I manually adjusted the HCV and when I do I can feel hot going through the hose on the cabin side, so I know that part is not blocked off, but the heat never makes it out the vents. Is there another place I need to adjust? I pulled out the radio but nothing was apparent. Any suggestions appreciated. 1993 FJ80.
 
Sorry to revist the dead thread, but is there anything else that needs to be adjusted to get heat? The slider in the climate control unit does nothing and I am not sure where the break is. All other functions of climate control work.

I manually adjusted the HCV and when I do I can feel hot going through the hose on the cabin side, so I know that part is not blocked off, but the heat never makes it out the vents. Is there another place I need to adjust? I pulled out the radio but nothing was apparent. Any suggestions appreciated. 1993 FJ80.
Check the that ventilation fan is working. That it's actually spinning.

Make sure the heat ducts are connected. Drivers side down by your knees under the panel. That can get dislodged or disconnected. It's a plastic duct just underneath the panel. Align the two pieces and push them together again.

Even if its disconnected, feel for heat underneath that DS panel. You should feel heat blowing with the heat turned up and the ventilation fan working.

Try that.
 
Sorry to revist the dead thread, but is there anything else that needs to be adjusted to get heat? The slider in the climate control unit does nothing and I am not sure where the break is. All other functions of climate control work.

I manually adjusted the HCV and when I do I can feel hot going through the hose on the cabin side, so I know that part is not blocked off, but the heat never makes it out the vents. Is there another place I need to adjust? I pulled out the radio but nothing was apparent. Any suggestions appreciated. 1993 FJ80.
As a sanity check, can you verify your engine is up to temp, and rear heat working?
After that, it could be a restricted heater core. You'll know this one by the air getting warmer the lower the fan speed.
After that, I'd suspect blend door
 
Here is a :banana: 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.
View attachment 168598View attachment 168600
Thanks for posting this. Very helpful.
 

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