AC condenser

smokinVE said:

80% is the “rule of thumb” when making the change to 134.

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I was not aware of this. Thank you.

Well I'm still at it and not sure where I went wrong. Each day for the past 2 weeks or so has been above 100*F down here. I typically change shirts 2-3 times a day due to sweat.

Hopped in the 91 to grab some parts (for my 05) and the AC never cooled down below 70*F in the cab. Threw the gauges on it and the low side was around 45psi, well above where I had left the pressure a few days prior. How did this happen? So I recovered some freon, brought the low side back down to 28psi -ish. It cools but I know it's still not right.

The condenser is removing about 10*F of heat measuring temp from outlet to inlet. Suction side is sweating at the TXV, evap drain is draining water. After talking things over with my dad, we looked at the OEM expansion valve and a spare replacement expansion valve I had on the bench. Same replacement expansion valve that is on the truck currently.

The replacement expansion valves are all adjustable via a screw on the high side/bottom of the valve body. I adjusted the one on the truck both direction and no significant changes were made to cabin air temp. With the OEM (likely original) expansion valve still handy, I decided to swap it back on and see what happens. I know this systems cools pretty good, because it was doing so for 10+ years. It wouldn't freeze you out, but it kept the sweat from running down your forehead.

Currently have the system under nitrogen pressure for 1hr, then the vacuum pump for the next 3 hours. Also wondering if I need to increase air flow across this new condenser via an electric fan to see optimum performance of the new condenser.

Chrysler valve on the left (and bottom), aftermarket replacement on the right (and top). Notice the Chrysler valve is marked 91, same year as the truck.

I also read that going by the sight glass for R134 and R410a is not a good indicator. Unlike R22 and R12. On those old freon types, if the sight glass was clear, your pressures were also good.

This truck really needs a larger compressor on the turbo to clean up some of the smoke. A 60 or 62 ideally. But I'm making myself hold off until I either figure out this AC issue, or weather gets cooler.

Learning everyday.

Well I made a 4 hour road trip last week in middle of the day and stayed cool the whole time. I also added more freon to bring the low side up to 48psi, eliminating my freezing up on the evaporator, which I knew would be an issue with low charge.
Relays purchased for blower motor power supply upgrade. If ambient air is below 95*, it's finally chilly in the cab.

Always learning.

I need to learn this stuff, my pressures are equal in my fummins. Both low and high side are around 110. Cools decent below 90 but I need to figure it out before I tear something up

What is your AC setup. Mix of Ford and Dodge parts? Does Ford use a orifice tube? If your low side is 110psi, hard to believe it’s cooling at all.

If you don’t have access to an AC machine that can pump the correct weight of freon into the system, you will need to add by the weight of each 12oz can.

If your truck was in my driveway and we didn’t know what the issue was, I’d starry with using nitrogen for leak checking. No leaks? Then flushing entire system of oil, drain and measure compressor oil, add correct oil amount, replace dryer, blow air through condenser and check for blockage, bolt up system tight, leak check again with nitrogen, no leaks, start vacuum down for 30 min, let sit. If it holds, continue vacuum for 3 hours to remove all moisture. Then you can add freon. Reference the R134 chart for pressure ranges given the outside ambient temp that day.

Easy mistakes to make are:
Not purging the supply line of ambient air each time you tap a new 12oz can of freon.
Not enough air flow across the condenser when adding freon. I have a squirrel cage blower set on a stand that blows right into the coolers. Also bump idle speed to 1200 rpm.
Add freon as a gas, not liquid. Can upside down, adding as a liquid. Can right side up, adding as a gas. Adding as a gas is slower, but easier on the compressor.
Have a bucket of water next to you and submerge half the freon can. This will help warm the can when adding. It’s difficult to add cold freon to a 75% charged system.
Place a thermometer in the middle vent inside the cab. Monitor temps as you add.
Check inlet and outlet temps of the condenser while adding. 10°F difference is normal, 3°- 5°F difference is a clogged condenser.
Do not overcharge! More is not better when it comes to freon.

Red Sleeper said:

What is your AC setup. Mix of Ford and Dodge parts? Does Ford use a orifice tube? If your low side is 110psi, hard to believe it’s cooling at all.

If you don’t have access to an AC machine that can pump the correct weight of freon into the system, you will need to add by the weight of each 12oz can.

If your truck was in my driveway and we didn’t know what the issue was, I’d starry with using nitrogen for leak checking. No leaks? Then flushing entire system of oil, drain and measure compressor oil, add correct oil amount, replace dryer, blow air through condenser and check for blockage, bolt up system tight, leak check again with nitrogen, no leaks, start vacuum down for 30 min, let sit. If it holds, continue vacuum for 3 hours to remove all moisture. Then you can add freon. Reference the R134 chart for pressure ranges given the outside ambient temp that day.

Easy mistakes to make are:
Not purging the supply line of ambient air each time you tap a new 12oz can of freon.
Not enough air flow across the condenser when adding freon. I have a squirrel cage blower set on a stand that blows right into the coolers. Also bump idle speed to 1200 rpm.
Add freon as a gas, not liquid. Can upside down, adding as a liquid. Can right side up, adding as a gas. Adding as a gas is slower, but easier on the compressor.
Have a bucket of water next to you and submerge half the freon can. This will help warm the can when adding. It’s difficult to add cold freon to a 75% charged system.
Place a thermometer in the middle vent inside the cab. Monitor temps as you add.
Check inlet and outlet temps of the condenser while adding. 10°F difference is normal, 3°- 5°F difference is a clogged condenser.
Do not overcharge! More is not better when it comes to freon.

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Appreciate the extended response. So it's using the ford compressor and lines, no dodge parts. Ford does use an orifice tube which I put in a new one. So last year I put it all together, charged with nitrogen and it held no issue. Pulled a vacuum on it overnight and it pulled down fine. Added correct amount of compressor oil and than charged it ususing a 30ib tank and ac gauges. I didn't charge by weight, I just charged until I hit the correct pressures according to ambient temp. I did make sure I purged the charge line of air. Worked great all last year but I noticed it was a little warm this year so figured I was low on freon. That's when I threw the gauges on and noticed noticed the low and high side are equal. How and why it's cooling I have no idea, just drove to Texas and back and she did fine, anything over 95 or 100 and it didn't cool well but anything below that and it still cooled but not like it should.

Was that pressure reading taken at idle? Any additional air flow across the cooler stack when reading was taken?

I’d bet you have a leak somewhere and the system is low on charge. Is it freezing up at all?

Red Sleeper said:

Was that pressure reading taken at idle? Any additional air flow across the cooler stack when reading was taken?

I’d bet you have a leak somewhere and the system is low on charge. Is it freezing up at all?

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At 750 rpm with the blower on high, no extra air flow across the stack but I'm using the 6.4 fan which is a monster compared to the Cummins fan. The line is not freezing up but it is cold and sweating. I don't know anything about this stuff, so being low on freon would make my low side high? I can try throwing some more juice to it but didn't want to mess anything up. Sorry for taking over your thread lol. Also I don't think I hear the compressor cycle, seems to stay on the whole time.

I did add the uv pag oil when I filled it last year, I'll hit it with my uv light and see what I can find

I almost wonder if you don’t have a cross leak between high and low side somewhere. It’s still odd that it’s cooling fairly well.

Look with the uv light. If nothing shows up, add some more juice. That high side needs to be a higher reading, around 300psi. No risk of over pressuring the system yet. There is likely a pressure relief valve on the compressor.

My 91 has a relief valve. That’s how I found out the condenser was plugged. High side spiked and relief valve opened.

Red Sleeper said:

I almost wonder if you don’t have a cross leak between high and low side somewhere. It’s still odd that it’s cooling fairly well.

Look with the uv light. If nothing shows up, add some more juice. That high side needs to be a higher reading, around 300psi. No risk of over pressuring the system yet. There is likely a pressure relief valve on the compressor.

My 91 has a relief valve. That’s how I found out the condenser was plugged. High side spiked and relief valve opened.

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Will do, I'll report back.

Couldn't find any leaks with the uv light, strapped the biggest fan I had to the condenser and threw some more juice to it and this is what I got. Cools worse if anything.

Did you try another set of gauges? Ac won’t work worth a cock with those pressures. Or I suppose a weird blockage could give odd pressures but that’s rare.

smokinVE said:

Did you try another set of gauges? Ac won’t work worth a cock with those pressures. Or I suppose a weird blockage could give odd pressures but that’s rare.

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No sir, I can try digging a set up though.

Can you measure the temp at inlet and outlet of the condenser? Should be around 10° when truck is stationary and fans blowing.

You are definitely overcharged now.

Ok with Smokin, find another set of good gauges or try your gauges on a working system. Flick the gauge face and see if the needle move around.

Well, buddy stopped over and totally dumbfucked me. For some reason I was taking pressure readings with my valves open on the gauges lol. Total brain fart. The truck cooled good unless it was over 90,ive added juice since then but it hasn't been that hot. Pressures are right where they need to be and it's blowing ice cold.

Fantastic.

So you did have a cross leak, just at the gauges. Makes complete sense. Glad you resolved the issue.

Red Sleeper said:

Fantastic.

So you did have a cross leak, just at the gauges. Makes complete sense. Glad you resolved the issue.

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Yeah me too, appreciate all the help.