Heater control valve not connected (3 Viewers)

[tasmaniandevil]

Hello,

Need help again.

The AC of my 97 LC stopped working, all warm air. Low pressure side is 20pis, high pressure side is 100 with 650 idle rpm. Put 4/5 can in, now I got 60 on low pressure side and 120 on high pressure side with 650 idle rpm. 40psi low pressure side and 150psi high pressure side with 1500 rpm. Temperature is 75-80F. Too high ?

The dash temperature didn't change at all.

People say the heater control valve cause problem sometimes. Mine seems not connected but the hot cold slide works ok, hot air came out instantly once moved over. The swing arm of the heater control moves accordingly.

What should I do next?

Thank you

 

[Fj80oregon]

the heater control valve has no control! Yes you need to hook up the valve correctly, you just need a couple hoses and clamps to achieve this. looks like someone bypassed the rear heater but did not know what they were doing. Search rear heater bypass and hook it up the correct way and you should be back up and running with cold air. Right now your heater core is getting hot coolant flowing through it and no matter how cold the AC is it can’t cool 185 degrees to 50.

 

[baldilocks]

You might consider replacing the hot water control valve. It looks old.

 

[Kernal]

@tasmaniandevil : Can you show us the other heater hose plumbing on the firewall, ie: middle and right taken from above and/or from the right looking at the firewall.

 

[tasmaniandevil]

the heater control valve has no control! Yes you need to hook up the valve correctly, you just need a couple hoses and clamps to achieve this. looks like someone bypassed the rear heater but did not know what they were doing. Search rear heater bypass and hook it up the correct way and you should be back up and running with cold air. Right now your heater core is getting hot coolant flowing through it and no matter how cold the AC is it can’t cool 185 degrees to 50.

I will do that. Thanks a lot. BTW, will it have impact on the ac manifold gauge? Right now I am high on the lower pressure side and low of the high pressure that.

 

[tasmaniandevil]

You might consider replacing the hot water control valve. It looks old.

Good point. Thank you

 

[tasmaniandevil]

@tasmaniandevil : Can you show us the other heater hose plumbing on the firewall, ie: middle and right taken from above and/or from the right looking at the firewall.

Thanks

 

[ZackR]

Not the photos I was expecting to see based on the title of the post!

I concur with @Fj80oregon 's post above. Order new valve and put it back together correctly before messing with the AC any further.

 

[Kernal]

OK, so the rear heater circuit was disconnected and left in place, the T pipe removed on the right, and front heater hoses rerouted directly to the front/main heater core pipes on the firewall. So as already mentioned above, your front/main heater will get hot coolant all the time no matter where the heat selector lever is positioned.

By the looks of the bracket for the rear heater pipes and other brackets in the photo (rusty) the rear heater pipes could have been rusted through and leaking, so the PO bypassed them in his own way. Where did the vehicle spend most of it's life?

@tasmaniandevil : If you haven't looked yet, get under the vehicle, look up, right side above the Catalytic convertors if your model has them (under the front right foot well and front right seat) and take some photos of the rear heater pipes, they are mostly hidden by heat shields but you can see some sections of those pipes.

 

[LongDuck]

Post #2 seems to nail it; the PO bypassed the heater control valve, and in doing so you now have hot engine coolant running through the heater core ALL the time, which the A/C can't overcome. If you need to bypass the rear heater because it's leaking, here's the correct way;

On one of my other cars, the A/C is so anemic that I bypassed the heater core so there's zero hot coolant going to it to maximize efficiency. In the Sonoran Desert every little bit helps,

 

[cartercd]

Once you get your plumbing sorted, see this post to set up the adjustment cable on the heater control valve Adjusting water valve to maximize A/C performance - https://forum.ih8mud.com/threads/adjusting-water-valve-to-maximize-a-c-performance.173731/

 

[Kernal]

Here's a photo showing the bypass hose (87245-60420)) you can connect to the right side of the heat control valve. AFAIK it's from a deisel 80 series
and not available from US dealers but may be from dealers in Australia??

Note that the hose coming up from the left side of your engine that is now going to the top pipe on the firewall needs to go to the left side of the heat control valve:

And here's a link to the discussion:

Rear Heater Delete Hose with a Factory look

When deleting the rear heater on an 80 series there a few ways to address the heater hoses. We at LCP offer a hose in both OEM or Gates for a factory look. Normally we are strong OEM supporters but because this hose see no high heat, vibration, and easy to get to we recommend the Gates hose...

forum.ih8mud.com

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The photo below show's another hose set-up method using a 90 degree molded heater hose to bypass the rear heater. Not that the original metal U pipe in the photo above is missing from your vehicle so this won't work unless you have the metal U pipe or the hose in the photo above.

The flow from the right side of the heat control valve doubles back and rearward into the top pipe on the firewall for the front/main heater core.

All hoses for deleting (bypassing) the rear heater water circuit are 5/8" ID (or metric equivalent):

 

[alia176]

@tasmaniandevil
Folks seem to be focused on your heater valve not connected, and who cares? You're wanting cold A/C, the heater valve doesn't even need to be in the engine bay so just forget about that for now. It's not winter, and you don't need hot water entering the heater core. You're in Houston so you need A/C stat!

So why is your a/c not putting out cold air even though your manifold pressure seems to be functional. You may want to find out what the pressure gauges should read given your ambient air temp at that time. Those pressures fluctuate if it's a 70 deg day vs a 100 deg day. 40 and 150 psi are possibly when the clutch isn't engaged and those are static pressures.

I'd start here in the FSM that you can download for free, then do a systematic troubleshooting. I did a quick search for manifold pressure gauge readings and what they mean in the FSM but wasn't able to find it. I feel like I've been seen it before in my hard copy.

The fact that you added almost a whole can of R134a makes me think you have a leak. Find out why your system lost freon, and where the leak(s) are. Chances are the leaks are junctions where O rings are present. Maybe one of them is bad, but that's where the search needs to start. I'm sure the FSM talks about all this.

After finding the leaks, drain the system of freon, replace the O rings, evac with a vac pump and follow all the steps after that. YT has vids on all this.

I believe the gauges should be read while the compressor clutch is engaged and the compressor is spinning. The engine needs to be at 1500rpm, blower on max cool, in recirc mode. Your vent temps should come close to 40deg, IIRC.

Here's what I do to find a leak if the system is already filled with r134a. Run the system, making sure the air comp is running. Then looks for leaks at every junction by spraying with a spray bottle of soapy water. When you see bubbles, you've found a leak. If you system has die in it already, then look for the telltale signs of UV die with a UV light and glasses.

 

[Kernal]

Yeah, we kinda got focused on the heat control valve bypass but then his truck has two problems.

One is that the way his water heater hoses are currently hooked up his front/main heater core will always be hot no matter the position of the HVAC Temp control slider. So even if he had working AC the air that is first cooled down by the Evaporator core will then be heated back up (some) by the always hot heater core. So that needs fixing.

The other is that his AC system apparently is not working/cooling.