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Need a little help with my AC on my truck

dbrannon79

I'm getting there!
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Location
Seguin, TX
Ok guys I’m in need or a little help with the AC on my truck. I’m preparing for a vacation trip in August with the family and the wife is telling me she’ll rent a car if I can’t get my ac to cool better!! I’d like to see it cool good going into the 104 degree summer months.

it’s always been barely able to keep 60 degree air at the vents and in a crew cab truck it’s kinda hard to stay comfortable in the southTexas heat especially when the humidity is through the roof!

this weekend I pulled the front grill and installed a couple of 12” condenser fans despite having very limited space with the trans and engine oil coolers in there I was able to make it work! There wired in with a relay to the clutch cycle switch so there only on with the compressor. Photo attached with them behind the grill.

Today I ran the truck at idle for about an hour watching vent temps, pressures, and condenser temps. My recirculating door motor is broken so I wedged something in there to keep the door shut to circulate air in the cab and not draw in outside air. Now I have a evaporator freeze issue! It’s almost 90 degrees outside and humid today too.

Before I did all this. My low pressures were always about 35 with the high side at close to 200. Vent temps stayed at about 60 unless it was really hot outside then it was up to 65-70 degrees. After I got the fans installed in front of the condenser pressures stayed about the same but vent temps were at 55 or so. Now that I’ve wedged the recirculating door shut I’m seeing 32 degree vent temps. Pressures have dropped to 25 low and 175 high. Condenser temps and now equal across at 125 degrees and the evap water drain has stopped drain due to the evap beginning to freeze up! Oh and all this with the blower fan on high.

One tap of the throttle and the compressor cycles so I added a little less that half a can of 134 and no change in pressures or temps!

about a year ago I had replaced everything on the ac, new compressor, dryer, oe fixed orifice, and flushed everything out since the old compressor had seized up. Do I need more Freon or is something else wrong I may need to check?
 

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Quick and dirty: does the inlet and outlet of the evaporator by the cab feel about the same cold temperature? Is the accumulator sweating?

If the lines are not the same temperature it's low on refrigerant. Evac and recharge the system. Have a local shop do it real quick if you don't have the tools. Check the R4 compressor for any signs of a leak at the body o-rings.

If the lines are both cold: Likely replace the low side switch on the accumulator esp if it's not a R134a part.

Evac and recharge because unlike the engine there isn't a dipstick to tell you how much refrigerant is in the system. Low on oil the engine locks up. Too much oil and you likewise have problems with the engine.

Too low on refrigerant and the ( oil needy 2 stroke engine style ) R4 will debris glitter bomb the system from no oil return with the refrigerant. Too much and the system tries to boil the excess out of the accumulator till it liquid slugs the compressor. The actual "oil level" in the system is another level of voodoo: generally if it didn't loose any you don't add any say with a slow leak.
 
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The low side switch should be for 134a. The truck is factory with 134. The evap “was” sweating its ace off before I shoved the recirculating door shut. Then it froze! I have my gauge set and a vacuum pump but not a scale to charge by weight. I know it’s not the proper way but I had charged it by quantity adding up the ounces on the can and the sticker that was in the old dryer, also watching the gauges. I’ve done that on many different vehicles and not really had issues when there wasn’t a restriction or what not

I just picked up a couple cans of 134 from Walmart. If it’s low it might be just half a can. Sadly when I redid the ac last year I had charged it with dye and I can’t find anything showing up fluorescent green as if there is a slow leak.
 
I had charged it by quantity adding up the ounces on the can and the sticker that was in the old dryer

This actually works if the system adds up to x number of whole 12oz cans. 👍I have avoided scales myself with systems capacities like this.

The low side switches are not reliable.

Did the airflow get restricted from the freeze up? What do you mean by Freeze up exactly. Frost on the pipes you can see isn't a concern.

You get the system a touch low and the R4 will get noisy and maybe give it up on vacation. It's critical the charge is correct and not a guess. Other systems like coughDodgecough are not as critical as the overly sensitive R4 design. It was a poor 1970's design on R12! Mediocre GM beancounters used it on factory R134A for a couple model years. :facepalm:
 
Did the airflow get restricted from the freeze up? What do you mean by Freeze up exactly. Frost on the pipes you can see isn't a concern.
The air flow hadn’t yet seem to get restricted with freezing but I did notice the water from the evap drain slow to almost nothing telling me it’s about to freeze up solid. Plus my vent temp was showing 32 degrees


When was the radiator last pulled and the whole stack cleaned?
I had replaced the tank on one side of the rad last year also. And when I was in there fitting the fans in place I used my compressor separating the stack blowing each one out
 
Absolutely nothing wrong with getting the weight by math of cans.

now vent is at 32? Don’t change anything yet. Make sure no ice is on the coils then do it again. If you are blowing 32- drive and enjoy.

A super common place to leak is the valves where you attach the hoses. So after charging a system, you will have dye on those valves. I wrap a shop rag around it to catch all the splatter and spray clean with brake cleaner. Then kill the shop lights or put over the blanket and turn on the uv light. Clean off all the dye from everything especially those valves. Then, when you want to check the system- first thing to do is uv light the valves and see if they have been leaking BEFORE attaching gauges. If they have been leaking- swap them out.
 
...I had replaced the tank on one side of the rad last year also. And when I was in there fitting the fans in place I used my compressor separating the stack blowing each one out
That may not have been enough. Once plugged it takes water with sufficient pressure to get it all cleaned out after the radiator is out by itself. The primary indicator is warm air at idle and cooling at speed.
 
I connected my laptop to bump the idle to a grand while I watched the system. The compressor began to cycle off and on about every 30 seconds but while running the high side never went over 200. Then I noticed the lines from the evap to the dryer and out from the dryer began to freeze. No air restriction in the vents yet but damn it’s cold inside the cab!FF4D1E32-4898-4B42-87FD-D38810A7D8F6.jpeg08CDE830-9995-4540-BC4D-FCF933AEEE6B.jpeg
 
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Just to make sure I wasn’t shooting myself in the foot. I grabbed a kitchen thermometer and a glass of ice water. Well the one I was using in the dash reading Celsius was off by about 3 or so degrees. I’m rechecking vent temps nowD4B86233-506E-4B48-9B79-8B6E60A303FE.jpeg
 
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Using the kitchen thermometer and recalibrated mine. I’m at 40 degree vent temps. Me like this! Hope my wife doesn’t jump on the truck with wet hair!! She’s gonna have icicles on her head 😂
 
Leave it alone at this point! The ice on the outlet of the evaporator indicates it has enough charge. If and only if the airflow stops from ice build up then replace the low side switch on the accumulator.
 
Ok I need to back up a minute. I turned the blower speed down to low and watched the vent temps. It slowly crept down to 38 degrees and now my entire dryer has iced up so has the line to the compressor but not all the way to the compressor yet.

I had to stop and think about what I’ve done up to this point. Blow out condenser and radiator, installed two condenser fans, then it started acting like it was low on Freon. So I added 1/2 a can.
Oh and forced the recirculating door closed.

I let it run a little while longer and finally the compressor cycles at 20 psi. I did this making sure my relay wasn’t back feeding into the compressor keeping it on.

With the dryer freezing over. Is this a problem?
 

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And how sure are you EXACTLY what refrigerant is in there?
These numbers all dont add up to r12, or r134a. This is acting like someone stuffed about half, maybe 75% your system with propane or butane.
Or if the full propane refrigerant (not pure propane, a mixture) - then they added more than normal. idk why I didn’t think of that before.

If you can hit the 32f barrier- leave it be. If it starts icing up- turn the blower fan up and might have to turn on a heater to melt the evap ice off in really humid areas.
 
@Will L. Not much difference in refrigerants at -5C see "propane" R134a comparison chart below. We have lots of fan going on, engine RPM, and a questionable charge level. Clearly the evap is not a low charge as the outlet is also icing up. I have seen this ice up before on a perfect system when conditions are just right esp. "high idle of 1200+ RPM".

@dbrannon79

Does the system have a $25 VOV in it or a standard $1.99 orface tube? The VOV would explain Will's question.

The quick and dirty test question wasn't answered - before you messed with adding refrigerant were the evaporator inlet and outlet near the same temp? If so one didn't need to mess with the charge.

I would replace the low side switch as it should kick out before the system hits ~20F by pressure. You should not be seeing a low side below upper 30's psi.

To fix the switch one should recover the system, replace the switch, and charge it. Skool of hard knocks: I have had many of the valves fail on the low pressure switch accumulator port and discharge the system attempting to swap it. One didn't even have a valve in it: that was exciting instant system discharge and we never found the bad low side switch. Wear goggles if you are going to gamble the damn thing works when replacing the low side switch.

It's possible the valve is bad (restricted) in the accumulator and the switch slowly sees the low pressure condition. More likely just the switch is bad though.


HC_compair.jpg
 
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And how sure are you EXACTLY what refrigerant is in there?
These numbers all dont add up to r12, or r134a. This is acting like someone stuffed about half, maybe 75% your system with propane or butane.
Or if the full propane refrigerant (not pure propane, a mixture) - then they added more than normal. idk why I didn’t think of that before.

If you can hit the 32f barrier- leave it be. If it starts icing up- turn the blower fan up and might have to turn on a heater to melt the evap ice off in really humid areas.
It’s just 134a in there. The only thing I changed was getting the condenser to cool better. Maybe too much!
 
@dbrannon79

Does the system have a $25 VOV in it or a standard $1.99 orface tube? The VOV would explain Will's question.

The quick and dirty test question wasn't answered - before you messed with adding refrigerant were the evaporator inlet and outlet near the same temp? If so one didn't need to mess with the charge.

I would replace the low side switch as it should kick out before the system hits ~20F by pressure. You should not be seeing a low side below upper 30's psi.

To fix the switch one should recover the system, replace the switch, and charge it. Skool of hard knocks: I have had many of the valves fail on the low pressure switch accumulator port and discharge the system attempting to swap it. One didn't even have a valve in it: that was exciting instant system discharge and we never found the bad low side switch. Wear goggles if you are going to gamble the damn thing works when replacing the low side switch.

It's possible the valve is bad (restricted) in the accumulator and the switch slowly sees the low pressure condition. More likely just the switch is bad though.


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I’m sorry I forgot to answer that one. The line from the orifice seemed about the same as the dryer just by grabbing by hand

I have the $1.99 standard orifice in there. I was curious about the vov one but I also knew before I did this I could spray a tiny bit of water on the condenser and it acted like it was under charged.

before I had redone the ac last year I had been researching about charging it with propane. I have used enviro-safe in the past on other vehicles but frankly the thought of using flammable gas and having the family with me in an accident scares me!
 
Well the trip home from work the ac wasn’t too bad. Took a bit to cool off with the cab temps at 140 degrees. It was in the low 90’s today, The vent temps got down to around 55 leaving the blower on high. As soon as I got home I grabbed my gauges to see how the pressures were. 45 low and around 225 high. I know I’m not gonna have perfect ice cold ❄️ air like the newer trucks but this is a major improvement compared to what it was. I just need to get the wife in the cab on a hot day to get her approval for the trip lol

I have the center console from a 2000 model Chevy between the front seats that I’d like to somehow plumb in the ac ducks it has for the rear. That would really be the bomb for better air circulation in the cab! I was thinking of running a tube to the floor vents but once I get the air box replaced in the dash but I don’t think I’ll be able to have air flowing through both dash vents and those rear vents at the same time. Any thoughts about where I could plumb into the dash without hindering the dash vents too much?
 
Hey guys, I figured I'd continue on this thread about my AC after our vacation trip. during the trip I noticed that as long as I stayed under 65 mph, the ac would cool great. vent temps would stay near 45 degrees while it was toasty outside! heat index was up near 105 degrees and rather humid. But when I was up near 70 mph and more, the vent temps would start to slowly climb near 60 degrees. I figured I was still a little low on freon (134A).

after we got back home from the trip I connected my gauges to see what was going on. a trip into town today I also noticed that it was taking a rather long time to cool down in the cab. gauges were showing 50 low and 275 high when I first turned on the ac. as I let it run a bit sitting in the driveway the pressures slowly came down to around 35 low, 225 high. vent temps were at about 50 degrees at idle and the blower on high. I turned on the high idle switch (1000 rpm) and watched it some more. pressures dropped some more to about 27 low, 200 high with vent temps near 42 degrees, blower still on high.

since I really couldn't replicate highway speeds at 70+ mph in my driveway I figured that the pressures would end up dropping further with the wind flowing through the front end causing the cycle switch to begin cycling the compressor on and off making the vent temps go higher in the cab. I had a half empty can of 134 in the garage. I dropped that in and watched to pressures. nothing changed! no lower or higher pressures. Now I'm questioning the amount of charge I have on it.

I knew I had disconnected the pusher fan that was mounted over the oil cooler, I started playing with it. as soon as I connected it the high side pressures started to rise, I assumed that was due to it pushing the heat from the oil cooler into the condenser. disconnecting the pusher fan that's mounted over the trans cooler made no change in the pressures. I am thinking that is because of the trans cooler doing the same thing.

as it was already suggested to do with the trans cooler, I am looking to try mounting both the engine oil and trans oil coolers in between the condenser and the radiator. unless there might be a better option for the oil cooler. I also plan to remove the second pusher fan and only keep the one fan mounted on the passenger side.

looking at the space I have between the radiator and condenser and the thickness of both oil coolers, I think I should be able to reverse the mounting brackets or make some steel flat straps and use the factory coolers in that location. I have already sealed off the open areas in the front support that would allow air to flow around the condenser with some thick foam.

what's yall's thoughts on moving both coolers so the heat from them isn't being pushed into the condenser? are there any detrimental effects on the engine by moving the oil cooler there?

once I have this done, I would like to evacuate the system completely, check the orifice for debris and maybe install a high temp vov orifice and recharge with the correct amount of 134a. All in the hopes that I'll be done and never have to look back!

P.S. would anyone have the correct 134a charge and oil charge spec handy for my truck?
 
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