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AC Still Not Blowing Cold

dconway32

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Hi guys,

Reaching out because I'm a little stuck and hoping for some advice on what to do next.

This is the first summer I've owned my K5 Blazer. So working out the issues that show up in summer time and unfortunately the AC has been a pain. I have 2 young kids that have to sit in the back and the AC is important to me so that they can ride in my truck without sweating to death. They haven't ridden with me in the truck since it's gotten really hot over the last 2 months. I live in Oklahoma so summers here get pretty hot. Typically mid 90's most days from June thru August. As I'm typing this up, it's about 94 outside right now.

So I have to get this thing working.

My build:
1986 K5 Blazer
350 w/ Holly 650 double pumper carb

AC is 134A

When I bought the Blazer back in February 2020, I tested out the AC and it worked very well and blew cold. It was about 60 degrees outside that day when I was test driving it before I bought it. It worked throughout March and April without issue, although I used it rarely during those months, but it did seem to work. I also got the windows tinted at 5% so it's pretty heavy tint. When it started warming up into the low 80's in May, I noticed that the engine was getting up to around 220 degrees when I was sitting idle for about 10 min or so. It never really peaked above 225 degrees, but I felt like that was pretty hot.

I also noticed that the AC wasn't working very well when it got hot outside. The service records showed that the AC and radiator system was installed within the last couple years brand new. So the first thing I did was check the AC charge. It showed that it was fully charged, so I assumed it was working.

It does blow a little bit cold at higher speeds (not ice cold like in my wife's new Camry), but then it would not blow very cold at all at idle.

I then assumed that maybe the fact that the engine was heating up to around 220 degrees during idle, that might do it. The engine dropped back down to 180 after getting back up to speed and the AC would cool down more too. Again, not ice cold, but somewhat cold.

So after doing a bunch of research, I decided to do a electrical fan conversion. Below is a picture of the new fan system that replaced the mechanical fan.

The fan I installed was the Flex-A-Lite 295 - Dual 13 1/12 inch fan system. Rated up to 4,600 CFM.

I got the fan install done last week and of course wanted to test it out. I ran out for some lunch in the peak heat of the day (about 95 degrees) and went to a local BBQ place known to have long wait times in the drive -thru (but it's pretty decent BBQ). Sure enough it took about 10 - 15 min or so to get my food. All that time, I left the AC on and kept it in drive as I sat idle in the food line. Before I installed the new fan, engine temp would have definitely gotten up to 220 - 225 degrees during that time. But with the new fan installed, it only peaked around 195-200 degrees during that time and as soon as I got driving again, engine temp dropped back to around 180 degrees.

So yeah!! seems like the engine temp issue is fixed..... But the AC has not improved at all. it still pretty much does the same thing.

I dropped a good chunk of money doing that fan conversion and before I spend more money, I wanted to reach out and see if there's any advice that you guys might have.

The compressor tested good and was fully charged. The system is new r134A and was installed 2-3 years ago brand new for the whole system. And now that the engine is not getting really hot and I have plenty of airflow coming through the radiator now which I assumed was the main issue.

I'm not seeing any leaks on my driveway other than the condensation drip from the AC accumulator, although I do feel like the accumulator sweats more than normal, but I could be wrong on that.

I did check the radiator and topped it off and all that.

I have about 500 miles left before I need to change the oil on it, so it's close to needing new oil.

Any advice would be much appreciated on this!

Thanks!
Dan
 

DB Cooper

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What are the low and high pressures with the compressor turning?
Without these numbers were just blindly guessing.
 

Wes Harden

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Pressure reading at idle in drive will help. The compressor may not be efficient at idle. 134a in old cars is not as efficient as r12.
Your ac\heater blend door may not be switching completely, and leaking hot air into evap case. If you by pass heater core or install a heater control valve. this might help. get an a/c thermometer, leave in the center regulator, max ac, at idle you 94 ambient and 50% humidity, low 60's would be best expected. cruising speed low 50's.

I added a 10" condenser fan to my system, for Hot Arizona summers. Fan only turns on with ac. What is the control for your fans always on? temp switch? 1 fan or both?
 

Blue85

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So system is entirely stock other than electric rad fans? Stock R-4 compressor, stock evap, stock condensor? What do you know about the conversion to R134a? Normally the orifice tube is swapped for a smaller one. Has the low-side pressure switch been adjusted? How do you know the charge is correct? Is the receiver/dryer cold? Line to the compressor? If you fire up the truck with a cold engine, does it seem to cool better then after the engine is warmed up? Have you verified the re-circulation (i.e. "MAX") mode is working?
 

Chevman88

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So system is entirely stock other than electric rad fans? Stock R-4 compressor, stock evap, stock condensor? What do you know about the conversion to R134a? Normally the orifice tube is swapped for a smaller one. Has the low-side pressure switch been adjusted? How do you know the charge is correct? Is the receiver/dryer cold? Line to the compressor? If you fire up the truck with a cold engine, does it seem to cool better then after the engine is warmed up? Have you verified the re-circulation (i.e. "MAX") mode is working?

Not to hijack this thread, but I'm having similar issues. Everything is new with a Sanden 508 compressor, parallel flow condenser, and r-134a low pressure switch. I'm trying to narrow down why my fresh air door isn't cycling to re-circulate the air and it doesn't look like it's getting vacuum to change. I've traced the vacuum line and it looks like it T's off to an actuator under the cowl and the other end disappears behind the air box.
 

dconway32

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What are the low and high pressures with the compressor turning?
Without these numbers were just blindly guessing.

I have a gauge set on order from Amazon along with a temp gun to test everything. Should be hear tomorrow. I had my mechanic take a look at it while it was in the shop for another thing. He said the readings on the compressor were good, but I don't remember what he said the specific readings were. I'll hook up the gauges once I get them in and report back asap.
 

dconway32

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Pressure reading at idle in drive will help. The compressor may not be efficient at idle. 134a in old cars is not as efficient as r12.
Your ac\heater blend door may not be switching completely, and leaking hot air into evap case. If you by pass heater core or install a heater control valve. this might help. get an a/c thermometer, leave in the center regulator, max ac, at idle you 94 ambient and 50% humidity, low 60's would be best expected. cruising speed low 50's.

I added a 10" condenser fan to my system, for Hot Arizona summers. Fan only turns on with ac. What is the control for your fans always on? temp switch? 1 fan or both?

I'll look into that blend door closer. When i switch the modes on the control panel it sounds like the vent door is switching back in there. I'll have to see if it is fully switching or not. I have the fans on temp switch. I'll take a look at those compressor fans. I'm sure it would help.
 

dconway32

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So system is entirely stock other than electric rad fans? Stock R-4 compressor, stock evap, stock condensor? What do you know about the conversion to R134a? Normally the orifice tube is swapped for a smaller one. Has the low-side pressure switch been adjusted? How do you know the charge is correct? Is the receiver/dryer cold? Line to the compressor? If you fire up the truck with a cold engine, does it seem to cool better then after the engine is warmed up? Have you verified the re-circulation (i.e. "MAX") mode is working?

The AC system is R134A and all components have been replaced with new. Not sure if the parts are "stock" or not. They look pretty standard. Not sure about the orifice tube. Service record doesn't go into that much detail. I confirmed the charge with one of those AC Pro gauges. It said it was full. My mechanic also check it and said it was full too. The AC cools about the same whether the engine is cool or fully warmed up. MAX mode seems to be working. When I flip it to MAX, the fan engages and blows air out of the vents. Not sure how else I can verify that the mode is working.
 

dconway32

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On another note, I went on a Starbucks run this morning when it was about 70 degrees out and the AC was blowing ice cold during the drive, sitting in the drive thru, and the return home. I had to point the vents away from me because it was blowing so cold. But then this afternoon, when I headed to the gym and it was about 85 degrees out or so, the AC was back to blowing "sort of cold" like what I described before.

This morning, I drove the truck long enough for it to fully warm up and the AC was still blowing ice cold.

Thoughts?
 

Wes Harden

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is ambient temp related. so on a hot afternoon with thermometer in vent, at idle or just off idle @1000-1500rpm, see what vent temp is. then grab a box fan and put in front of grill blowing in to rad. If vent temps go down you need more air going through condenser.
 

dconway32

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is ambient temp related. so on a hot afternoon with thermometer in vent, at idle or just off idle @1000-1500rpm, see what vent temp is. then grab a box fan and put in front of grill blowing in to rad. If vent temps go down you need more air going through condenser.
I just installed the Flex-a-lite 295 electric fan system that's rated for 4600 CFM, so I'm confident in saying that I have plenty of airflow going through the rad now. The AC pretty much blows at the same temperature whether idle or moving. I have a temp gun on order and will be here tomorrow, but as of now, I've basically been determining temp by putting my hand up to the vents while at idle and driving and the air basically feels the same. Before I installed that electric fan, that wasn't the case. Before the new fan, it would blow a little colder while driving down the road and then when I stopped it would blow warm.

Now with the new fan system it blows "sort of cold" consistently. Except, apparently, when it is 70 degrees or below outside when it is blowing ice cold as I mentioned above.

Is there something other than airflow that I'm not thinking of maybe?
 

Wes Harden

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Since your system cools when it is cool out, the doors are probably good.
IDK which orifice tube you have, but there is a variable one available. Most conversions recommend this. 134a needs higher operating pressure on discharge side. A 134a pressure switch. Should be used.
 

Wes Harden

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Still says is condenser, it not doing it's job when ambient temps are up.

Edit electric fans are not the end all be all, that hot rod mags would have believe.
Search here there are numerous threads.
 

Blue85

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What triggers the fan? Is it only coolant temp, does it run whenever the clutch is engaged or is it on a high-side pressure switch?
 

Blue85

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That's what I was getting at. If it's running without a fan sometimes, it probably has a high-side cutoff switch or it would have vented refrigerant already. (Edit: R12-R134a retrofit kits often include that switch. Sort of quasi-legal-requirement, but only because R134a sucks. Pressure is higher and system won't cool as well, but with good fans and good shroud sealing can come close.)

You don't really need the fans at speed, but at low speed or parked they should always be on when the compressor is running. You just need a diode or two on (each) fan relay
 
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