More air conditioning

[Motorgod0]

Hi all. I’m new here, post little, visit often. I get a lot of good info just by searching and it is appreciated. I posted this in another area because I wasn’t sure where to put it. Anyway I’m starting a new post because I had no luck searching. I’m trying to get more air out of my AC. I have a 90 Suburban 5.7, front and rear AC. Replaced the blower fan, replaced resistors, cleaned out debris from everywhere I can reach, sealed the ducts, washed the vanes and checked all grounds. Fan blows and compressor spins. System was charged by the shop but I don’t know the pressure. However the gauge on an AC recharge kit puts it in the green. It just feels like the fan isn’t powerful enough or pushing a lot of air. I know it’s not a modern 2020 vehicle and don’t expect it to freeze me out but it just seems as though there should be more. Maybe it’s maxed out and I just don’t realize it. Thanks in advance.

 

[westsoundred]

if I turn on the a/c in my 1992 K1500, I need gloves and mittens. It should absolutely freeze you out, the pumps on these trucks were awesome.

i don't know if there is any coloration, but the previous owner of mine had hard wired the compressor to a toggle switch under the steering column. Its a hack i want to correct, fwiw, but the controller may have failed at one point. It could be your issue too (?)

 

[deadbeat]

I think you should be getting around 38 - 42 degree air out of your vents on MAX AC on high blower. If not, something is not right. At those temps if your fan is working anywhere near right it should get really cold in there. I think you could maybe use a meat thermometer if it goes low enough to verify you temps coming out, and you may need to hold the throttle around 1k at first.

 

[deadbeat]

You can try putting a fan ( house fan) in front of the grille and letting it blow in, if this makes a difference your clutch fan may not be working up to full potential.

 

[Motorgod0]

Thanks. I’ll look at both suggestions. I appreciate it

 

[885speed]

I used to be in the same/similar boat as you when I used to daily drive my old 88 Camaro with the same situation of a retrofitted R12-R134a system that I always felt it just didn't blow hard enough, when in reality it just wasn't blowing cold enough. I got maybe on a good day 55 degrees out of the vents, it blew "cool" but not cold enough to really cool the inside of the car down to make it comfortable. Marginally better than having the windows down, at best.


Okay, so I've got a couple potentially helpful(I hope) suggestions. How deep you go depends on just how cold you'd like to get.
Just to preface, although my truck is a 97 and has a differently designed a/c system than yours, it'll absolutely freeze me out on even the hottest of days.

With your truck being built in 1990, it was designed to run with R12 before it got outlawed in vehicles and converted to the R134a that it's charged with now.
While the conversion to R134a will work fine as it sits, you'll still lose cooling capacity using R12 components.

You're in luck, because GM did update the a/c systems to better handle the R134a.
Hopefully this info can help steer you in the right direction, I'm not sure how compatible all the newer R134a parts are to the older trucks. But it's worth your time to check it out.

1. Condenser.
If the condenser in your truck is original, then there is a huge possibility that it is the older "tube and fin" design and probably pretty crudded up too.
Mild: You could take your grill off and use an appropriate cleaning/foaming solution to clean out much of the crud and gunk in the rad/condenser.
Wild: Do some research and see if you can change the condenser to the one best suited for R134a which is referred to as a "parallel flow" condenser.

2. Clutch fan.
Mild: Double check to make sure that your fan clutch is in good working order, gotta have that airflow.
Wild: You can change your mechanical fan which is most likely the plastic fan, to the heavy duty fan which is made of metal and has more blades for greater airflow.
I believe these came on the 454 and diesel trucks IIRC.

3. Orifice tube.
The one in your truck is likely pretty nasty, and again not best suited for the current refrigerant.
One popular option used as an upgrade/mod across many different vehicles seems to be the "blue" Ford orifice tube. IIRC the OEM application of these were late 90's Thunderbirds.
Also, if you pull the old one out and is really black and nasty then it's time to seriously consider a new compressor and a good flush of the lines/evap core.

4. Receiver/dryer.
Anytime the a/c system is opened up, it's good practice to replace this as there is a desiccant bag inside of it that absorbs contaminants in the a/c system.
It's likely that it's original also. If you're feeling frisky you can even wrap it in insulation and MAY see a slight increase in performance, maybe.

5. Evap.
This one is plain and simple, just make sure that your evap core is clean and doesn't have any leaks.

6. Compressor
Your truck has what is referred to an "R4" type compressor. I can say from first hand experience that these things are J.U.N.K. and have very well known design flaws.
They just don't have the same performance, let alone the reliability of newer compressors.
Mild: If your compressor has ANY signs of the common failure points, strongly consider getting a GOOD quality NEW replacement R4 unit. DO NOT buy ANY re-manufactured compressors... EVER.
Wild: Do some research and upgrade the garbage R4 style compressor to the newer "Sanden" type, similar to what came on newer trucks like mine. There are companies out there on the interwebs that sell parts/kits you can use to retrofit the Sanden compressor on your truck. It'll most likely require the most amount of research/money spent, but in conjunction with everything else listed, you should be able to get your truck into the low 40's. Or even in the 30's like my truck (best measured temp of 39)


Probably worst case scenario, is you may have to have a/c lines made if nothing else is out there that is compatible. If older/newer trucks of our body style had the compressors on the same side it would be even easier to do.

Maybe someone who has done this already will chime in and add some details.

Also, one last thing. If you do change major components to non OEM ones, I would strongly recommend getting a set of manifold gauges and charge the system yourself. Unless you go to a shop that really knows their stuff and is particularly knowledgeable about a/c work, I'd be willing to bet that they'll just charge it with what the book says it should have and send you on your way with a poorly charged system.

 

[thinger2]

Hi all. I’m new here, post little, visit often. I get a lot of good info just by searching and it is appreciated. I posted this in another area because I wasn’t sure where to put it. Anyway I’m starting a new post because I had no luck searching. I’m trying to get more air out of my AC. I have a 90 Suburban 5.7, front and rear AC. Replaced the blower fan, replaced resistors, cleaned out debris from everywhere I can reach, sealed the ducts, washed the vanes and checked all grounds. Fan blows and compressor spins. System was charged by the shop but I don’t know the pressure. However the gauge on an AC recharge kit puts it in the green. It just feels like the fan isn’t powerful enough or pushing a lot of air. I know it’s not a modern 2020 vehicle and don’t expect it to freeze me out but it just seems as though there should be more. Maybe it’s maxed out and I just don’t realize it. Thanks in advance.

Get a probe type meat thermometer like a chef uses. Stick it in each dash vent and compare the temps. Then do the rear vents. You will have loss at the rear for sure but it helps to determine if you have a stuck blend door (real common)
Make sure your ac clutch isnt skipping.
Look for metal dust around the clutch.
Dont trust the guage on any ac recharge kit. Get an actual set of ac gauges.
Some parts stores have them in their loaner tool program but inspect them real close before you use them.
Make sure the gaskets are in the fittings and make sure the threads are good.
If it leaks, you can loose all of your refrigerant.
Dont add any refrigerant untill you check the charge pressure.
Overfilling the system will seriously screw it up.

 

[Schurkey]

I’m trying to get more air out of my AC. I have a 90 Suburban 5.7, front and rear AC. Replaced the blower fan, replaced resistors, cleaned out debris from everywhere I can reach, sealed the ducts, washed the vanes and checked all grounds. Fan blows and compressor spins. System was charged by the shop but I don’t know the pressure. However the gauge on an AC recharge kit puts it in the green. It just feels like the fan isn’t powerful enough or pushing a lot of air.

88Fivespeed covered most everything. There are some additions I'd make.

1. Your post talks about VOLUME of air, not TEMPERATURE of air. Stuff a thermometer into the ducts front and rear, VERIFY THE TEMPERATURE of air you're getting. A/C thermometers are cheap and readily available. I keep one in every vehicle I have as a tell-tale for day-to-day performance of the HVAC system. For example,
https://www.amazon.com/Robinair-10597-Dial-Thermometer-220°F/dp/B000O3M5CE/ref=sr_1_9?crid=2CZ42PRMULC9R

2. Just as important, you NEED to know the high-side and low-side pressures of the refrigerant. Manifold gauges of quality construction are not horribly expensive. It could be that some parts stores might rent them.
https://www.amazon.com/Robinair-49134A-Aluminum-Manifold-Couplers/dp/B004QA7MAQ/ref=sr_1_29

3. You should have a low-amperage current probe and an accurate multimeter; or MAYBE a multimeter that will accept 20-amp short-term amperage measurements. If you're using a multimeter as an ammeter, put a 9- or 10-amp fuse in-line because the internal fuses in the multimeter can be scary expensive. You need to know the VOLTAGE right at the HVAC blowers when they're turned up to "High"; because low voltage will mean insufficient blower speed. You should know the AMPERAGE DRAW of the blowers on high speed; excess amperage means there's problems in the blower assembly--worn brushes, scored armature, shorted windings, etc. In MY garage, I look at the amperage pattern on an oscilloscope. Then I can calculate the blower RPM as well as seeing that each armature bar is working properly and "in balance" with the other armature bars.

Without knowing the true temperature of the air, and the pressures of the refrigerant, and the voltage (at least, voltage and amperage is better) at the blower motors, EVERY THING ELSE IS GUESSWORK.


It's REAL COMMON for the HVAC air box to fill up with leaves, pine needles, sparrows, coconuts, and the crap is hard to get OUT of the evaporator or heater-core fins. It's not hard to imagine having to remove or maybe replace the evap or the heater core because they're packed with air-blocking debris.

Beware air leaks between the cowl and the plastic inlet to the blower fan; and between the various plastic ducts under the dash. The joints are sealed with foam gasketing; the foam rots and ambient air leaks "under the dash" which gives you a cold cab in the winter, and a warm one in summer.

 

[Motorgod0]

Thanks everyone. Looks like I’ve got some work to do. I’ll let you know how it goes

 

[PlayingWithTBI]

You're in luck, because GM did update the a/c systems to better handle the R134a.

^^^X2
When you work with an A/C system, you need to spend the $$$ to do it right, the biggest bang for your buck is flushing the system and new updated parts, ie; the OE orifice tube s/b upgraded to one for 134A, the condenser s/b a parallel flow (as mentioned above). If your system doesn't have a high pressure shutoff switch on the back of the R4 compressor, you need to put one in and wire it in series with the low side switch. if you buy a new R4 compressor you need to check the air gap on the clutch and set it to 0.020" - 0.030", it is a pressed fit, the nut just holds the clutch from coming off. When installing the compressor you should make sure it has ~4oz in the compressor (after adding it rotate the compressor to disperse the oil before installing it) and another 4oz in the accumulator. Here's a snip from a build sheet from my 88, YMMV. HTH


Accumulator/Drier 60-30640 Buy Auto Parts Amazon $46.00
A/C Flush 6545-6 Johnsen's 32oz can Amazon $15.84
A/C Condenser 7-4168 Spectra Premium Parallel Flow Amazon $74.98
PAG oil FJC 2484 FJC Viscocity 46 Amazon $9.94
Orifice tube ADO-15-5378 AC Delco For 1999 up (R134a) Summit Racing $2.99
High Pressure switch 35961 Murry 200 on/430 off O'Reiley $37.99
A/C Compressor ADO-15-20185 AC Delco With clutch (new) Summit Racing $169.99

BTW you need something like this to flush the system
https://www.amazon.com/CHEEFULL-Con...hvlocphy=&hvtargid=pla-4584276302514406&psc=1