Dash AC issues

Topic: Dash AC issues (Read 1901 times) previous topic - next topic

Dash AC issues

May 28, 2023, 07:39:19 pm

Dash AC wasn't cooling well when we went to top the fuel and propane tanks last weekend. Have not needed it since last summers vacation. Thanksgiving vacation was cool enough it seemed to work well.

Thought it was just low on Freon so I hooked up the gauges and set the high idle with evap fan on high.

Compressor runs continuously, condenser fans only cycled a couple of times when high side hit about 225 psi.

I'm no AC expert so I thought I would put this out for suggestions. Here are the gauge readings.

Re: Dash AC issues

Reply #1 – May 28, 2023, 09:50:41 pm

Your low side is running very low pressures. In the second photo it's in a vacuum. Somebody more knowledgable than me will hopefully respond but it looks low on refringerant to me. Is your condensor fan not running continuously? That doesn't seem right.

Re: Dash AC issues

Reply #2 – May 28, 2023, 09:53:18 pm

I'm am sure that DSD will respond soon enough and let you know about those gauges and their readings.

Re: Dash AC issues

Reply #3 – May 28, 2023, 10:05:00 pm

I believe the condenser fan should run as soon as the AC is turned on so you should find out why
it isn't running continually.

Re: Dash AC issues

Reply #4 – May 29, 2023, 01:40:10 pm

The first thing I'd do with your low side reading is add a can and see what happens.

Re: Dash AC issues

Reply #5 – May 29, 2023, 02:58:41 pm

Quote from: Dave Larsen – May 29, 2023, 01:40:10 pm

The first thing I'd do with your low side reading is add a can and see what happens.

I added a couple of pounds, only thing changed was the High side went up. 🤷‍♂️

Re: Dash AC issues

Reply #6 – May 29, 2023, 03:11:39 pm

Get your fan working continually the Freon needs to be cooled. If it isn't cooled the evaporator
can't cool properly.

Re: Dash AC issues

Reply #7 – May 29, 2023, 05:26:50 pm

The condenser fan motor on mine was cycling also. It was the resettable breaker going off and on. Replaced the fan motor and it has worked ever since.

Re: Dash AC issues

Reply #8 – May 29, 2023, 08:15:36 pm

You might have a restriction in the system. Usually if the low side is in a vacuum the expansion valve is clogged but you normally won't have very high on the high side either.

Re: Dash AC issues

Reply #9 – May 29, 2023, 08:40:12 pm

Update:

I was able to get the AC working this afternoon, I had concluded that the expansion valve was stuck or just failed entirely. With 225 psi on the high side and zero or even a vacuum on the low side, a restriction in the system seemed logical. The most likely place being the expansion valve. I had intended on ordering a new one and a dryer today but NAPA was closed. (Memorial Day) so when I returned from work I thought I would try hooking up the gauges again. No change, low side almost zero and high side around 225 psi.

There is a "Hail Mary Method" we use at work that sometimes results in success. So I took my rubber handle phillip head screw driver and gave the expansion valve several "whacks" and I be danged......the low pressure rose! so..... I gave it a few more aggressive "whacks" and pressures returned to what I thought they should be. ( 30 to 35psi) the condenser fans started running when the high pressure reached around 240 and the condenser temp reached whatever temp the trinary switch cycles at.

FYI.... the condenser fans on ours are controlled by a Trinary switch.
Definition: A/C Trinary switches combine low and high-pressure compressor clutch cut-off functions plus an electric fan engagement signal at 254 psi. The low-pressure cut-off of these trinary switches is 30 psi and the high-pressure cut-off is 406 psi. Perfect usage when running electric fans.

I may still need to change the TX expansion valve, I replaced it and the dryer just a few years ago, but for now its working and I think I'll leave well enough alone. Plans are to try it a couple more times before our summer vacation, if no issues, we hit the road.

I want to thank everyone for their replies and suggestions, nice to know that there is always members willing to help.
Great forum to be a member of.

Re: Dash AC issues

Reply #10 – May 29, 2023, 08:41:14 pm

You nailed it Red Tractor

Re: Dash AC issues

Reply #11 – May 31, 2023, 02:05:58 pm

Last year I had someone put refrigerant in my dash AC system. It ran for a while well but I noticed when I tried it recently I wasn't getting any cold air again. Last year I bought the required equipment to put freon in or vacuum the system out but don't really know much about how to use it and haven't tried learning yet. I need to stop and get some refrigerant and try hooking the system up and seeing what happens..
Glad you got it figured out though. And thanks for posting it.

Re: Dash AC issues

Reply #12 – May 31, 2023, 02:55:14 pm

Justin, last couple of coaches I was involved with had massive corrosion in the receiver dryer. Im suspecting you have the same issues. I cant give you a logical explanation to the corrosion, the system in theory should be sealed and completely dry/sealed. Nevertheless I really recommend replacing the dryer. Once you have it removed Im betting if you cut it open as I have you will see the problem. At that point I have flushed out the pressure hose to the expansion valve and replaced it. Dont want to contaminate system any more if possible. Having a recovery system helps a ton.
Scott

Amazon.com: Universal Air Conditioner RD 8214C A/C Receiver Drier : Automotive

Amazon.com: 1600 A/C Expansion Valve Peterbilt Truck AirSource NEW : Automotive

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Re: Dash AC issues

Reply #13 – May 31, 2023, 03:57:55 pm

If it gives me anymore problems .... I'll replace the TX valve and the dryer. I'll check my records to verify but I think I replaced them both in 2018.

Re: Dash AC issues

Reply #14 – May 31, 2023, 11:04:10 pm

How difficult is it to access the expansion valve? I assume the dash has to be mostly disassembled?

Re: Dash AC issues

Reply #15 – May 31, 2023, 11:21:28 pm

Foretravel recently worked on my dash air and my dryer was replaced by them and the system worked again. My dryer was only three years old. Hmmmm.

Re: Dash AC issues

Reply #16 – June 01, 2023, 07:33:45 am

Quote from: Geodmann – May 31, 2023, 11:04:10 pm

1. How difficult is it to access the expansion valve?
2. I assume the dash has to be mostly disassembled?

1. 0n some coaches one of the hose nuts can be the hardest part of the job due to how the expansion valve is installed.
2. Yes but once you get started it is just a bunch of those square headed screws. Take pics as you remove sections of the dash just in case you have a honey do come up.

Mike

Re: Dash AC issues

Reply #17 – June 01, 2023, 07:39:07 am

Quote from: Realmccoy – May 31, 2023, 11:21:28 pm

Foretravel recently worked on my dash air and my dryer was replaced by them and the system worked again. My dryer was only three years old. Hmmmm.

If you have the system opened to atmosphere it is best practice to replace the dryer.

Mike

Re: Dash AC issues

Reply #18 – June 01, 2023, 09:30:56 am

Quote from: Geodmann – May 31, 2023, 11:04:10 pm

How difficult is it to access the expansion valve? I assume the dash has to be mostly disassembled?

On our 95 U280, just remove the front grill, (4 latches) and its right there. Hardest part it removing the sticky insulating material on the valve and fittings.

Re: Dash AC issues

Reply #19 – June 01, 2023, 10:54:48 am

Quote from: Geodmann – May 31, 2023, 11:04:10 pm

How difficult is it to access the expansion valve? I assume the dash has to be mostly disassembled?

On my 2001 it is under the wiper motor and forward of the evaporator. It was a pain to change. The sticky tar material prevents condensation on the cold valve. It must be reinstalled.

Re: Dash AC issues

Reply #20 – June 01, 2023, 05:56:50 pm

Quote from: FourTravelers – June 01, 2023, 09:30:56 am

On our 95 U280, just remove the front grill, (4 latches) and its right there. Hardest part it removing the sticky insulating material on the valve and fittings.

you're just bragging now...

Re: Dash AC issues

Reply #21 – June 01, 2023, 07:29:17 pm

Quote from: Geodmann – June 01, 2023, 05:56:50 pm

you're just bragging now...

well.......the 95's are something to brag about!

For those with a good ole' 95 GV with similar AC, these are parts that I have used.

Dash AC -
Evap blower NAPA # BK_6551744
Sanden compressor #4664
PAG100 oil
Napa #208317- filter /dryer
Napa #207376 - TX valve
Condenser fans -AV1110 (Amer. Volt)

Re: Dash AC issues

Reply #22 – June 01, 2023, 07:47:55 pm

And Justin.
You left out how many pounds of Freon. We recharged a few weeks back and put in 3

I noticed there were no bubbles in the sight glass so maybe we're good. I guess we'll know after a few hundred miles in this Arizona heat.

Re: Dash AC issues

Reply #23 – June 01, 2023, 09:10:48 pm

Quote from: Bob & Sue – June 01, 2023, 07:47:55 pm

And Justin.
You left out how many pounds of Freon. We recharged a few weeks back and put in 3

I noticed there were no bubbles in the sight glass so maybe we're good. I guess we'll know after a few hundred miles in this Arizona heat.

Well..... Bob, I left out how many pounds of freon because I don't know.

Maybe some AC guru on the forum here will know and chime in? I have a 30lb bottle and after vacuuming the system down, I fill with 134A until I get a good pressures on the high side based on the chart and hope the low side looks good and bubbles are mostly gone.

DISCLAIMER: I am no refrigeration expert...... I read, then try to remember what I've read long enough to put it in practice.

Re: Dash AC issues

Reply #24 – June 01, 2023, 09:29:03 pm

Easier to weight the bottle before and after to get a good idea or if you are anything like me3... pick it up before and then again after...then put it up and forget to weigh it at all.

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