Dash ac recharge on class a diesel pusher

mike brez wrote:

dougrainer wrote:

Ivylog wrote:

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Bingo. HOW can air get into a pressurized system? IF the system has been open to the atmosphere, then yes, find the leak, then Vacuum and charge. Vacuum can also let you know if the system has a large leak. Small leaks that happen under pressure, a Vacuum test rarely is accurate. Now, HOW is a novice supposed to know how much 134a to install? Unless you have your gauges connected and do a digital temp at closest outlet to the evaporator, you will have a hard time getting it filled correctly. BTW, SMALL leaks will not cause Oil loss. TOO MUCH 134a is as bad as too little. Too much and the system will not cool correctly just like too little. A TEST for posters. HOW much 134a(lbs) do you think a average Diesel RV motorhome takes? Doug

A diesel pusher about 3-4 lbs

Trick question. For most Diesels 2.0 to 4.25 lbs. BUT Some large diesels(usually Spartan) built after 2014 from 6 to 8 lbs. Doug

rgatijnet1 wrote:

dougrainer wrote:

Ivylog wrote:

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Bingo. HOW can air get into a pressurized system? IF the system has been open to the atmosphere, then yes, find the leak, then Vacuum and charge. Vacuum can also let you know if the system has a large leak. Small leaks that happen under pressure, a Vacuum test rarely is accurate. Now, HOW is a novice supposed to know how much 134a to install? Unless you have your gauges connected and do a digital temp at closest outlet to the evaporator, you will have a hard time getting it filled correctly. BTW, SMALL leaks will not cause Oil loss. TOO MUCH 134a is as bad as too little. Too much and the system will not cool correctly just like too little. A TEST for posters. HOW much 134a(lbs) do you think a average Diesel RV motorhome takes? Doug

If the system is still pressurized then who cares how much freon the system holds? All you really need is a thermometer. Placed in the outlet of one of the ducts, add freon slowly until the temperature drops to it's lowest and starts to go back up. As soon as that happens, you stop. You are right, too much is as bad as not enough so you add for the lowest temp reading.
Now this is not scientific and is not how a tech would do it but for a NOVICE, it will work just fine and probably save them a lot of money.

This is true. You watch the temp gauge and when the temp stops at a certain temp, you wait until it raises a degree or 2. Then STOP the fill. BUT, a lot of novices will not do that and will overfill. Doug

I have been in the HVAC industry for a little over 45 years and I have to say, this has been a fun post to read. Thanks everyone.

You can look for leaks yourself. when I had this problem I checked all the fittings and hoses, I noticed an oily substance on a switch, mine was a trinary switch some are binary they heve either 2 or 3 wires going to the switch. I changed out the switch and added a can or two of 134 and it has been good for about 6 years now. I think the kit I bought at Adv Auto and it came with a pressure gauge, a can of 134, a can of 134 with dye and a ultraviolet light pen all for $20 on sale. I wiped every thing down and saw no leaks with the ultraviolet light.

dougrainer wrote:

Ivylog wrote:

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Bingo. HOW can air get into a pressurized system? IF the system has been open to the atmosphere, then yes, find the leak, then Vacuum and charge. Vacuum can also let you know if the system has a large leak. Small leaks that happen under pressure, a Vacuum test rarely is accurate. Now, HOW is a novice supposed to know how much 134a to install? Unless you have your gauges connected and do a digital temp at closest outlet to the evaporator, you will have a hard time getting it filled correctly. BTW, SMALL leaks will not cause Oil loss. TOO MUCH 134a is as bad as too little. Too much and the system will not cool correctly just like too little. A TEST for posters. HOW much 134a(lbs) do you think a average Diesel RV motorhome takes? Doug

A diesel pusher about 3-4 lbs

dougrainer wrote:

Ivylog wrote:

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Bingo. HOW can air get into a pressurized system? IF the system has been open to the atmosphere, then yes, find the leak, then Vacuum and charge. Vacuum can also let you know if the system has a large leak. Small leaks that happen under pressure, a Vacuum test rarely is accurate. Now, HOW is a novice supposed to know how much 134a to install? Unless you have your gauges connected and do a digital temp at closest outlet to the evaporator, you will have a hard time getting it filled correctly. BTW, SMALL leaks will not cause Oil loss. TOO MUCH 134a is as bad as too little. Too much and the system will not cool correctly just like too little. A TEST for posters. HOW much 134a(lbs) do you think a average Diesel RV motorhome takes? Doug

If the system is still pressurized then who cares how much freon the system holds? All you really need is a thermometer. Placed in the outlet of one of the ducts, add freon slowly until the temperature drops to it's lowest and starts to go back up. As soon as that happens, you stop. You are right, too much is as bad as not enough so you add for the lowest temp reading.
Now this is not scientific and is not how a tech would do it but for a NOVICE, it will work just fine and probably save them a lot of money.

Ivylog wrote:

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Bingo. HOW can air get into a pressurized system? IF the system has been open to the atmosphere, then yes, find the leak, then Vacuum and charge. Vacuum can also let you know if the system has a large leak. Small leaks that happen under pressure, a Vacuum test rarely is accurate. Now, HOW is a novice supposed to know how much 134a to install? Unless you have your gauges connected and do a digital temp at closest outlet to the evaporator, you will have a hard time getting it filled correctly. BTW, SMALL leaks will not cause Oil loss. TOO MUCH 134a is as bad as too little. Too much and the system will not cool correctly just like too little. A TEST for posters. HOW much 134a(lbs) do you think a average Diesel RV motorhome takes? Doug

Guys I work at a car dealership we see cars every summer 3-5 years old that blow cool not cold. The Freon over time soaks into the rubber hoses or yes seals start to leak and a recharge will last another 1-3 years. If I have to to recharge 1 time a year I'm fine with it. Wondered how hard it is to do it. The radiator/condenser is easy to see and clean which I do every year. Just did not want to bring Rv to the store or have to bring a machine home vs a can and a recharge hose kit. I will look at it this weekend when kids can give me some time to inspect

crasster wrote:
Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.

Really, How is air going to get into a system that is still cooling, but not as cold as normal... is still pressurized and has enough freon in the system to work somewhat? Even while working the low pressure side will have 60+ psi in it... how is air going to get in???

Really - while you can DIY recharge, it is BEST if you can put the system under a deep vacuum then charge. It's the proper way to get all the air out so there is more pure 134a.