Wes's Burb build/update/maintance

[Wes Harden]

Just got home this afternoon, burb breezed east on I40 75+mpg. Having only the front air, was barely cutting it. 105+ outside, trans stayed below 180*, engine temp gauge 3/8 to 7/16.
Found my package from Western Alternator, thanks @500$k5. looks good, only it has the wrong pulley, came with the serpentine, I need the V belt. Also no pig tail for small connection. Any way happy to be home for a minute, off to Phoenix Sunday meet my daughter for D day.

Purtty

 

[Wes Harden]

Spent the afternoon replacing the rear blower motor. The new 1 I purchased, four seasons 35373, is a single speed, the original is actually a 3 speed but only use 2.
Rear air unit is A-R-A dealer install. I could not find any part numbers for ARA anywhere online.
Got lucky and had an old blower unit in my junk pile. Came out of truck like @ktmoutfront Tonka truck.
Splice and solder new leads, a total new 12ga ground, old had 2 splices and 2 sizes of wire.
Gonna run it tomorrow.
Might have a slow leak and am low on freon again.

 

[Wes Harden]

test drove the the a/c to hardware store and gas station. 107° today, would warm up to 100 parked and get down below 90° in a few minutes, but never below 80°.
Pulled into shop ,104° in shop, let it sit for a bit, hooked up the gauges, low side was 32 psi and high 212, seemed a little low, best temp from center or right vent 72° got 68 ° at rear evap.
Now I liked the low 30psi reading at accumulator, thought the high pressure was low. But vent temps are to high for low 30 pressure reading. Since the high was way lower then expected close to 300 psi i figured it was low on r12. I added a bit, both low and high pressure went up 48 and 270psi, vent temp dropped to 65°, fixed 1100 rpm.
the 47 psi low side pressure bothered me. Cracked open the 1974 GM light duty truck service manual, find a chart, C/K 3.25pd front system 110° 29-33psi LS, 250-270psi HS and 49-56° at vent. < is not what I was seeing.
C/K rear air 5.25pd system 110° 37-47psi LS 270-300psi HS, and 66 from right vent. < This is very close to what I was seeing.
So I am trying to figure why having the 2 front and rear evaps make a difference on pressures with 1 compressor.


Oh and I have a leak, added 12oz in April and now probably close to the same in June.

 

[6872xtc]

Those little things can definitely be frustrating. Having to go back in and redo things... Aarrghh!!

 

[Joel Wilson]

Those little things can definitely be frustrating. Having to go back in and redo things... Aarrghh!!

I know this may sound messed up, but the more troubles Wes has with his AC, the more I learn, cause I know squat about AC. I can troubleshoot the electrical side with my eyes closed and hung over, but the mechanical side, not so much. And I like the way Wes approaches things, very methodical.

 

[6872xtc]

I know this may sound messed up, but the more troubles Wes has with his AC, the more I learn, cause I know squat about AC. I can troubleshoot the electrical side with my eyes closed and hung over, but the mechanical side, not so much. And I like the way Wes approaches things, very methodical.

I understand your angle!
It's great that Wes posts up about it all.

 

[Joel Wilson]

test drove the the a/c to hardware store and gas station. 107° today, would warm up to 100 parked and get down below 90° in a few minutes, but never below 80°.
Pulled into shop ,104° in shop, let it sit for a bit, hooked up the gauges, low side was 32 psi and high 212, seemed a little low, best temp from center or right vent 72° got 68 ° at rear evap.
Now I liked the low 30psi reading at accumulator, thought the high pressure was low. But vent temps are to high for low 30 pressure reading. Since the high was way lower then expected close to 300 psi i figured it was low on r12. I added a bit, both low and high pressure went up 48 and 270psi, vent temp dropped to 65°, fixed 1100 rpm.
the 47 psi low side pressure bothered me. Cracked open the 1974 GM light duty truck service manual, find a chart, C/K 3.25pd front system 110° 29-33psi LS, 250-270psi HS and 49-56° at vent. < is not what I was seeing.
C/K rear air 5.25pd system 110° 37-47psi LS 270-300psi HS, and 66 from right vent. < This is very close to what I was seeing.
So I am trying to figure why having the 2 front and rear evaps make a difference on pressures with 1 compressor.


Oh and I have a leak, added 12oz in April and now probably close to the same in June.

I know squat about AC, so bear with me. Could the evap on the front system be clogged or partially clogged? Or maybe a leak in the ducting causing a drop in temps at the vent? Isn't there a dye that you can put in the system that will help pinpoint the leak? I understand that you are now retired and probably work harder than you did while employed.

 

[Wes Harden]

All of the above, is possible.
I have in the last year or so had the plenum out, got a peek at at the evap, looked clean, and repaired poor blend door sealing. Also closed up many gaps, from missing/desintergrated foam.
It has performed better in recent past, before compressor style change.
Dye works, I may end up doing just that. We shall see

 

[Clutternavyblue]

This is my first time responding in any Forum but I sympathize with this situation and wanted to help. I just went through all of this A/C frustration on my 89'. Same symptoms as you have described and went about replacing everything I could. Front and rear factory A/C converted to R134 using a remanufactured R4 compressor, a parallel flow condenser, and replaced lines, accumulator and blower motor. I ensured all of my controls and blend doors were in functioning order as well as proper vacuum routing. My system held perfect vacuum and we filled with correct (at the time) amount of R134. Dang thing was still blowing warm air. I went down the rabbit hole on this and discovered a few things that got my system working better.

1) The front and rear systems share a compressor and refrigerant but use different types of regulation. The front uses a orifice tube but the rear uses a expansion valve. This expansion valve is self regulating depending on the temperature of the refrigerant coming out of the evaporator. It has a thin copper line leading from the expansion valve with a bulb or coil at the end and is clamped to the output line of the evaporator. I'm not sure how it works exactly but if that sensor bulb/coil is not securely clamped to the output of the evaporator, the valve cant accurately control the flow of refrigerant. Mine was not, this led my system to open the rear expansion valve too much. My fix was to zip tie and insulate the sensing element to the return line. I noticed an substantial drop in vent temperatures. I wish I could tell you the difference in gauge readings this single step made but I didn't take readings.

2) At the time I was checking all of my vacuum lines and blend doors, I found a "T" in the vacuum line behind the glove box. One line lead to the passenger kick panel and one went.....well, I didn't know where. I poked the internet and ill be damned if a vacuum operated "outside air door" lives under the cowl on the passenger side. On the "max" A/C setting the cowl door should close and the passenger kick panel door should open allowing for recirculated air. My cowl door was broken at the hinge, meaning it would never shut. This allowed the hottest of air from the "plenum" (for lack of a better word) to keep entering the air box. "Plenum" as in the open space just under the windshield. This area gets super hot from engine heat and I believe my front evaporator had a difficult time cooling this air. My fix was to fabricate my own door, sealing it from the hot air and drawing cool air from inside the Suburban. Again, this helped tremendously, especially when sitting at stop lights.

3) This made the most difference and something I wish was done first. When the system was charged we did it at 1k rpm. Readings looked good and had coolish air. My truck has 700, 4.56 gears, and 255/85 R16s. she lives at 2400 rpms and at those revs the low side A/C pressure would pull down below the cutout point for the compressor. Its was constantly cycling the compressor and because of the loud tires, I couldn't hear it turning off and on. The internet suggested to check A/C gauge readings with rpms at cruising speed leading to this revelation. I put about another half pound of R134 in to sustain proper pressure across my RPM range.

I am happy to report I can get my air down to high 40 degrees running down the road with it warming up to about 55 at stop lights.(working on this too) I have since added a electric fan in front of the condenser to supplement my factory fan and clutch as well as installed a heater core by pass valve from Vintage Air. This valve keeps the hot coolant out of the heater core and subsequently helps keep the HVAC box a little cooler. I am not a mechanic and I might be way off base on some of this stuff but it does blow cold air now. Results may very but I hope this helps.

 

[Wes Harden]

Thanks for the time to share your experience.
Not sure the pre 80s trucks have the second outside door. I regasketed my kick panel door, and noticed much less heat and air flow with the a/c heater off .
This mid morning fired her up a/c running max, hooked up and launched boat. Thermometer in center vent got below 60. Might have been 100 outside.
The test will this afternoon when I head home.
Still having low voltage issue low rpms, under 1k
Pic is yesterday all off parked in shop

 

[6872xtc]

Voltage reading low in the dash voltmeter? Or with a DMM? Curious about the meter that you are observing, but I would bet that you have verified what you dash gauge is reading. So could it be a poor connection in the back of the fuse panel to the engine/chassis harness?
Possibly the ignition switch terminals?

 

[Wes Harden]

I'm am going by the dash. When at idle it'll drop below 10 volts, and I can hear things run different. Up the rpm and it sound normal, and meter gets to 13.
I haven't had time put the @500k5 alt on, tomorrow's project. Fingers crossed

 

[6872xtc]

So.... too busy playing to work on the truck, ehhh??

 

[Joel Wilson]

I love my powiermaster Alternator. 140 amps at idle baby. Far, Far cry from that crap at Vatozone

 

[Wes Harden]

5ish pm at boat ramp. 109* ambient. Full Heatshield in the windows, inside burb temp 120*.
Full ac, by the time boat is out, center vent is down to 70ish.
Gain 500 feet in just under 2 miles. If I use 3rd gear truck gets hotter than I like, 2nd gear temp guage stays in the middle, 25 mph and @2500 rpm. Mid guage is @200* as measured with infared, at t stat.


Havasu Gorge

 

[Wes Harden]

Swapped the alt, had to modify the lower bolt spacer, it interferes with small plug.
Charges 13.8 to 14.1 at 750 rpm both AC's on and aux battery in low state of charge. Happy, forgot to add lights in while testing.

Last pic is test card from Power master alt that wasn't up to the task.

 

[Joel Wilson]

Swapped the alt, had to modify the lower bolt spacer, it interferes with small plug.
Charges 13.8 to 14.1 at 750 rpm both AC's on and aux battery in low state of charge. Happy, forgot to add lights in while testing.

Last pic is test card from Power master alt that wasn't up to the task.

View attachment 417690

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View attachment 417693

I've had to modify a few alternator brackets along the way too. I just got tired of replacing them and bit the bullet and got the biggest that would fit. I really like the test cards they do

 

[nitro_rat]

I have a 1984 Sub, Q jet, 350, 700R4, 3.73 10 bolts, 32x11.50’s or 33x12.50’s (depending on what was cheap and available). It’s no speed demon but it goes just fine. All stock but tires, just for reference.

 

[76zimmer]

Great A/C info sharing! I too know squat about A/C, so its another bit of learning for me as well. At some point I will be installing an aftermarket system in my 76CCDRW, so whatever I can pick up here is a bonus for my learning the systems!
good luck Wes!

 

[Wes Harden]

I need to improve my cooling system. Towing the boat last Friday engine temp rose up well past 200°, and sounded like diesel, even with 91 octane on top of 5 gl of av gas.
I know I have a high static compression ratio. Been doing some research on dynamic compression ratio. Couple of items I realized I am fighting. As ambient temps and load go up higher octane would be needed, for my current set up, and that having higher than normal DCR I need to keep my engine temps down around 170°.
On my Colorado trip 91, and either VP octane boost, or AV gas, was sufficient, ambient temps were well below 100° for that trip. Friday was 109° and the boat weighs 3200 pd + trailer, I will probably have increase AV gas during the hot months, short term solution.
I would still like to improve the cooling. My temp gauge normal operation runs at @ 3/8 from cold. This is @ 175° to 180° at t stat confirmed with infrared thermometer.
The middle line is 195° to 205°. Friday the gauge got close to the 3/4 line. I found if used 2nd gear and raised the rpm the temp would cool off to the middle line.

Now the radiator is a new HD 4 row brass core, new brass heater core, block was flushed, June 21. Severe Duty Hayden fan clutch with Derale 19" 6 blade fan. 170° t Stat. Water pump is the only old part, original to engine build. Engine timing is @ 4° btdc, before I retarded it yesterday.
So do I need better air flow or water flow ? I know I get both with higher rpm. I am tempted to swap n a 160° t stat. I need to find out if the coolant is running through the radiator to fast or to slow.