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 > dashboard A/C on the fritz

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ernie1

Sacramento,California,USA

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Posted: 09/09/17 05:28pm Link  |  Quote  |  Print  |  Notify Moderator

I think that the ac system is possibly low on refrigerant and the unit is acting like it is. When the system is first started, the low side will have about the same pressure as the high side until it is run for awhile and the low side will continue to drop in pressure until approximately 20 psi at which point a low pressure cut out switch will disengage the clutch on the compressor to protect it from damage. Allowed to sit for awhile, the low side pressure goes up past the low pressure cutoff point and the unit will work again. A set of refrigerant gauges will confirm the state of charge or, if there is a sight glass in the system, look for bubbles. If the system is low on refrigerant, be sure you know what you are doing before attempting to recharge it.

klutchdust

Orange, California

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Posted: 09/09/17 08:42pm Link  |  Quote  |  Print  |  Notify Moderator

classctioga73 wrote:

So this morning I took the rv for a ride. It blew cold air for about 5 minutes then just regular temperature air. I turned the knob to off and tried to turn it back on and no air came out at all. I turned the setting to floor and it worked. I turned the knob to off and back to vent and no air, then I turned it to floor and no air
Are these symptoms all related to a bad blend door box??



It still has freon in it, otherwise it wouldn't cool at all. If it were my rig here is what i would do.

Open the hood engine off, locate the AC compressor and become familiar with the clutch mounted on the end. Have an assistant start the rig then turn on the A/C. See the clutch engage. Now have them duplicate the scenario that you described, always watching the clutch. If they experience no air and the clutch is still engaged then I would focus on the door mixer. If the clutch disengages it most likely has air in the system and is building up high head pressure in the compressor. They kick off around 300 psi on refrigeration systems not sure on autos.

Easier way is to go to auto store that loans tools, you need gauges for 134a. You can't put them on wrong, the ports are sized differently.Install those start the engine and observe the pressures. Look up a basic R134a temperature pressure chart and you can see the numbers that you are aiming for. Ambient temperature changes everything. They offer cans now with a hose attached that works well however an air conditioning system does not use freon like an engine uses oil, you have a leak somewhere. One of my cars used a can a year. With the gauges on you can observe the high side(big numbers PSI) and the low side . If the low side goes into a vacuum you need freon, if the high side goes to a big number and the clutch disengages then you have an issue with air in the system.

The gauges won't blow up. Be sure they are in the off position before you start and leave them there. Check for that sight glass too. Usually mounted low, like bottom of radiator low about dime size glass. If the engine has been running for 5 minutes and there are bubbles, you have troubles.

ernie1

Sacramento,California,USA

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Posted: 09/09/17 10:37pm Link  |  Quote  |  Print  |  Notify Moderator

Wow! It blows my mind what sort of info is given out. Having been an ac tech for a couple of years I have this bit of advice to the op: if you have to depend on the advice you glean from this site it's is obvious that you don't know enough nor have the proper equipment to correct your problem and should take it to a professional to have the ac repaired. This will save $$$ and you won't expose yourself to the dangers of exposure to refrigerants.I will have nothing further to say.

klutchdust

Orange, California

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Posted: 09/10/17 09:00am Link  |  Quote  |  Print  |  Notify Moderator

ernie1 wrote:

Wow! It blows my mind what sort of info is given out. Having been an ac tech for a couple of years I have this bit of advice to the op: if you have to depend on the advice you glean from this site it's is obvious that you don't know enough nor have the proper equipment to correct your problem and should take it to a professional to have the ac repaired. This will save $$$ and you won't expose yourself to the dangers of exposure to refrigerants.I will have nothing further to say.


What exactly are the "dangers of exposure to refrigerants" The op wants to know some basic refrigeration techniques to which he did receive some. Now if he were asking how to recover and replace refrigerant that's another story. Installing gauges does not expose one to your dangers to exposure statement. He is checking to see if his mixer door is working properly, big deal.

ernie1

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Posted: 09/10/17 01:06pm Link  |  Quote  |  Print  |  Notify Moderator

I know, I wasn't going to comment further but here goes. Sudden release of refrigerant will freeze and burn your skin especially your eyes. Releasing refrigerant in an atmosphere where there is combustion occuring like your engine running or a person smoking a cigarette can produce a byproduct called mustard gas. Ever hear of that? If enough refrigerant is released, in a closed environment like a garage, one can become asphyxiated. It's enough to worry me.

ernie1

Sacramento,California,USA

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Posted: 09/10/17 01:11pm Link  |  Quote  |  Print  |  Notify Moderator

Installing and removing gauges will directly expose one to the refrigerant especially if it is not handled correctly and refrigerant comes blowing out at 350-400psi which is NOT an unusual condition.

klutchdust

Orange, California

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Posted: 09/10/17 05:53pm Link  |  Quote  |  Print  |  Notify Moderator

ernie1 wrote:

I know, I wasn't going to comment further but here goes. Sudden release of refrigerant will freeze and burn your skin especially your eyes. Releasing refrigerant in an atmosphere where there is combustion occuring like your engine running or a person smoking a cigarette can produce a byproduct called mustard gas. Ever hear of that? If enough refrigerant is released, in a closed environment like a garage, one can become asphyxiated. It's enough to worry me.


Well I asked you that question for a reason. Having worked with sea going refrigerated shipping containers for over thirty years with a crew of sometimes 25 men I have never experienced nor heard of anyone being injured by the scenarios you presented. Having worked in some brutal outdoor situations using 230/460 motors we managed to come out of it unscathed. Not sure where your information came from or who told you that but sounds a bit dramatic. Sure, maybe those things could happen , I haven't seen it.

ernie1

Sacramento,California,USA

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Posted: 09/10/17 06:27pm Link  |  Quote  |  Print  |  Notify Moderator

klutchdust- I picked up this info while I was attending classes in Mechanical Engineering Technology in which I majored and got my college degree. I worked for two years as an ac tech repairing and installing auto ac units. What info I stated is very common knowledge in the industry. Don't take my word for it, check it out yourself.

Actually after leaving the ac repair trade I acquired another college degree and became a public health inspector for 30 years. People would call our office and complain of burning eyes and shortness of breath. Found out their ac systems were leaking refrigerant which is colorless and odorless, and the gas fired heating system was burning the refrigerant and turning it into a toxic gas which is heavier than and settles on the floor. This is mustard gas!

klutchdust

Orange, California

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Posted: 09/10/17 07:45pm Link  |  Quote  |  Print  |  Notify Moderator

ernie1 wrote:

klutchdust- I picked up this info while I was attending classes in Mechanical Engineering Technology in which I majored and got my college degree. I worked for two years as an ac tech repairing and installing auto ac units. What info I stated is very common knowledge in the industry. Don't take my word for it, check it out yourself.

Actually after leaving the ac repair trade I acquired another college degree and became a public health inspector for 30 years. People would call our office and complain of burning eyes and shortness of breath. Found out their ac systems were leaking refrigerant which is colorless and odorless, and the gas fired heating system was burning the refrigerant and turning it into a toxic gas which is heavier than and settles on the floor. This is mustard gas!


Check the MSDS on R134a, it's not flammable. Now back to the original poster. It is safe and easy to install refrigeration gauges on your vehicle without fear of armageddon occurring in your neighborhood. One thing about engineers, they always simplify everything.(eyes rolling)

pauldub

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Posted: 09/10/17 09:37pm Link  |  Quote  |  Print  |  Notify Moderator

Not that anyone is likely to be buring refridgerant, but "Chemical hazards R134a vapours decompose when exposed to high temperatures with the formation of toxic and irritating compounds such as hydrofluoric acid, carbon monoxide and carbonyl fluoride."

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