‘91 Suburban A/C Cooling Help

gmbellew said:

I've messed with mine a bit, and i think the door is warped. So the vent settings are more like bilevel. Bilevel is like 75% floor. For AC, having a vent/floor split really is OK as it cools off high and low up front and the rear comes in high from the back. On heat, it seals up tight and only comes out the floor.

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If I suck on the hose for the actuator, it closes the door and all the air comes out up top, so either I got a hole in the hose or a the valve for the selector on the back of the climate panel is bad.

I'm glad I came across this thread. I've been struggling with my 84 Suburban, with dual air, to get the temps down where I want them, and it seems the condenser is the likely culprit.

134 in general needs a good condenser, especially when we're trying to cool off these glass barns with bad insulation

Just a general note about it though (not geared towards anyone in particular, legitimately just a note for anyone reading about conversions and cooling challenges like this), remember that if the vehicle came with R12, there are general "conversion factors" for the new charge that should be considered ballpark at best. Then once you start changing components, all of that goes out the window.
It needs to be charged according to pressures and temperatures, preferably by someone familiar enough that they fully understand what they are seeing vs just "Charging until the vents seem about right". Parallel condensers are almost always a great idea if you need more performance, but they may make the vehicle more sensitive to exact charge amounts, depending on the rest of the system. Swapping the orifice tube can help as well, but again, needs to be done by someone competent, like they have had schooling for AC plus a decade of experience, or at least a half dozen successful conversions themselves. If that's the person reading this, then great, but if not, find someone who understands it, at least the first time. Bonus if they can weigh in charge along the way and tell you what was installed, so that in the future, you can charge by weight. You might find that what you saved by not taking it to someone was lost in recharging the gas and extra components you didn't know were needed the first time and/or burned up by improper oil etc.

Drove on the highway for sustained speed at 75 for a half hour, mid 40s at the vent and had to turn it down to medium-low up front and low in the back, it got cold quick in there!

91burb2500 said:

Drove on the highway for sustained speed at 75 for a half hour, mid 40s at the vent and had to turn it down to medium-low up front and low in the back, it got cold quick in there!

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Thanks Again, added link to spreadsheet.

My A/C never worked all that well - I'm thinking the parallel condensor might be in my future if I can get it running reliabily again.

I have gauges but only a small passing knowledge of what I'm seeing. Finding that person with years of experience on these older systems is becoming rare - I can't even find a shop to work on the mechanical aspects because "thats too old"....

Hunter79764 said:

134 in general needs a good condenser, especially when we're trying to cool off these glass barns with bad insulation

Just a general note about it though (not geared towards anyone in particular, legitimately just a note for anyone reading about conversions and cooling challenges like this), remember that if the vehicle came with R12, there are general "conversion factors" for the new charge that should be considered ballpark at best. Then once you start changing components, all of that goes out the window.
It needs to be charged according to pressures and temperatures, preferably by someone familiar enough that they fully understand what they are seeing vs just "Charging until the vents seem about right". Parallel condensers are almost always a great idea if you need more performance, but they may make the vehicle more sensitive to exact charge amounts, depending on the rest of the system. Swapping the orifice tube can help as well, but again, needs to be done by someone competent, like they have had schooling for AC plus a decade of experience, or at least a half dozen successful conversions themselves. If that's the person reading this, then great, but if not, find someone who understands it, at least the first time. Bonus if they can weigh in charge along the way and tell you what was installed, so that in the future, you can charge by weight. You might find that what you saved by not taking it to someone was lost in recharging the gas and extra components you didn't know were needed the first time and/or burned up by improper oil etc.

Click to expand...

I went through with the condenser upgrade and got the Spectra Premium one. It was well built, came with new mounts, and was painted black to boot. It is smaller than the old one by 20% percent, but it works well.
I also found out I had a bad evaporator. When I put the system together three years ago, I was on a tight budget and didn't buy one. The old one had a ding in the tubing where the orifice tube went and I simply sanded down the casing of the new Ford Red orifice tube to get it to fit. I'm pretty sure it never sealed right.

As a side note, the newer evaps have more surface area on the fins due to increased perforations.

After charging the system slowly via the 'JungleEddy' method, I got really good temps coming out of both evaps with quick pull down even in high humidity/ high temp weather (95F and muggy). After setting the new cycling switch to the appropriate pressure, it was getting 38* after running on the highway in the middle of the heat and mid fifties at idle after removing heat soak.

The system specs:
- A new Four Seasons R4 I got three years ago. It was a bit noisy until I added a little more oil to the system (12oz total now, specs called for 11 for R12), and now it is much quieter.
- Factory 7-blade mechanical fan with new heavy duty clutch (not severe duty)
- 88-98 blower motor
- Factory shroud for SBC modified to fit behind an aluminum 4-core equivalent radiator
- Red Ford Orifice tube (.062)
- 12oz of AC PRO Ice32 Ester oil
- new TXV for rear evap (I made sure the bulb was place correctly and is insulated well)

The rest of the system is stock, but I did reseal the heater box and lub all the doors and replaced the heater core while I was there.

I plan to add a pusher fan at some point to improve the idle functionality, but I'm pleased for now.

Sounds like you got it pretty dialed. Mine is still working great, but I am fighting with the vacuum side now. I found a broken line where it passes through the firewall, but that repair made no difference. I think my selector valve is bad as I have good suction on the supply line going into it. Based on the service manual, there are multiple actuators that need to move when the system is set to max A/C, I am only getting movement on the recirculation actuator, everything else is basically staying in default as I am getting air from the dash, floor, and a little from the defroster. Moving to defrost gives more air up top, but still getting it everywhere else.

Problem is the number that I need is basically unobtanium at this point. The Suburban has 6 ports, but only uses 5 with the 6th being "sealed in connector" per the manual. Anyone know if there is another vacuum valve that would work besides 16037769/15-17220?