Tuercas viejas
MB Enthusiast
I can proffer some info on mobile A/C systems since i have been working on this stuff since I was about 18 years of age.
I am now in my Golden years and that means more than 50 years experience working on all types of stuff!, not just cars . I have passed by proctored exam passing EPA certification in the USA to dispense and repair A/C system for profit.
Now before we get to gauges a good A /C tech mechanic "feels up" the job!
Harkening back to me yunger yurs I apprenticed under a good master mechanic called Eric from Mevagissey. Ex Bosun Wartime RN he reminded me of the following.
Look m'lad always feel the system up like you wuz feeling up a nice looking woman in the pub. --Like when I wuzah went ashore!
The thin un's are hot, can burn yah--but the fat 'uns are cool & comfortable like and like being felt up unless something is wrong and they can burn yah too!.
Use this to diagnose A/C systems, that's how it done in the Royal Navy below decks! --Feel the pipes--the fat uns are cool, thin uns are hot!
Never forgotten these words of Cornish maritime wisdom!
Re-gas that's strange word to use!
T'was never used when I went to college in Gloucester & Chelt'nam --Recharge with refrigerant more like!
Yanks would laugh their heads off using that term in a shop! Latinos too!
Must be zummut to do with the EEC!
The reason is, that in some parts of the system its a liquid refrigerant and then in some other parts its in a gaseous state . If any of these conditions are changed then the system won't work properly!
Briefly the refrigerant leaves the compressor in a gaseous state, but flowing through the Condenser (keyword condenser--Condense ) it changes to a hot liquid! --How hot ? Well depends upon the air coming into the Condenser but there's a ram air effect when are driving the car and a fan sometimes to cool it if it start to overheat cos it can't reject heat fast enough sometimes !
Now the Yanks invented A/.C --a Mister Carrier no less ! They also invented R12 a lovely refrigerant. Why do I say that?
Well simply put whatever the pressure you read on a gauge on the HIGH side is the actual temperature of the refrigerant and in the LOW side when in gets injected into the evaporator=-EeH Vap o- Raetor suggest a vapor --it boils as a gas. The system pressure drops to about 18 to 22 DgF as it comes out of the expansion valve which is again the temp inside the evaporator ., That level of cooling or boiling refrigerant sucks the heat out of the cabin, then returns to the compressor as a vapor .
Generally speaking when talking of R12 the high side is 2.5 times ambient on a good running system and about 25 dgf is good on the low side.
Nowadays we use R134a which is a much less efficient refrigerant so it cannot reject heat as well as R12 . So expect to see about 250 to 275 on a fairly hot day and about 32 /35 on a gauge on the low side --feel the cold on the fat pipes! But be careful with the thin uns! The temp could be about 250 F
Can burn yah!
OK with that in mind
I will comment on a few overlooked things and might be able to explain what is going on the the inoperative system mentioned in this thread.
Tuercas Viejas
I am now in my Golden years and that means more than 50 years experience working on all types of stuff!, not just cars . I have passed by proctored exam passing EPA certification in the USA to dispense and repair A/C system for profit.
Now before we get to gauges a good A /C tech mechanic "feels up" the job!
Harkening back to me yunger yurs I apprenticed under a good master mechanic called Eric from Mevagissey. Ex Bosun Wartime RN he reminded me of the following.
Look m'lad always feel the system up like you wuz feeling up a nice looking woman in the pub. --Like when I wuzah went ashore!
The thin un's are hot, can burn yah--but the fat 'uns are cool & comfortable like and like being felt up unless something is wrong and they can burn yah too!.
Use this to diagnose A/C systems, that's how it done in the Royal Navy below decks! --Feel the pipes--the fat uns are cool, thin uns are hot!
Never forgotten these words of Cornish maritime wisdom!
Re-gas that's strange word to use!
T'was never used when I went to college in Gloucester & Chelt'nam --Recharge with refrigerant more like!
Yanks would laugh their heads off using that term in a shop! Latinos too!
Must be zummut to do with the EEC!
The reason is, that in some parts of the system its a liquid refrigerant and then in some other parts its in a gaseous state . If any of these conditions are changed then the system won't work properly!
Briefly the refrigerant leaves the compressor in a gaseous state, but flowing through the Condenser (keyword condenser--Condense ) it changes to a hot liquid! --How hot ? Well depends upon the air coming into the Condenser but there's a ram air effect when are driving the car and a fan sometimes to cool it if it start to overheat cos it can't reject heat fast enough sometimes !
Now the Yanks invented A/.C --a Mister Carrier no less ! They also invented R12 a lovely refrigerant. Why do I say that?
Well simply put whatever the pressure you read on a gauge on the HIGH side is the actual temperature of the refrigerant and in the LOW side when in gets injected into the evaporator=-EeH Vap o- Raetor suggest a vapor --it boils as a gas. The system pressure drops to about 18 to 22 DgF as it comes out of the expansion valve which is again the temp inside the evaporator ., That level of cooling or boiling refrigerant sucks the heat out of the cabin, then returns to the compressor as a vapor .
Generally speaking when talking of R12 the high side is 2.5 times ambient on a good running system and about 25 dgf is good on the low side.
Nowadays we use R134a which is a much less efficient refrigerant so it cannot reject heat as well as R12 . So expect to see about 250 to 275 on a fairly hot day and about 32 /35 on a gauge on the low side --feel the cold on the fat pipes! But be careful with the thin uns! The temp could be about 250 F
Can burn yah!
OK with that in mind
I will comment on a few overlooked things and might be able to explain what is going on the the inoperative system mentioned in this thread.
Tuercas Viejas
