Purpose of sightglass

[ahsanonline]

The car is a 95 corolla.

A canister is fixed up front beside the condenser. It has a sightglass in it. Whats its use?

[whiteangel]

The sight glass is on top of the drier/receiver. For older systems using R12 refrigerant, you could tell if the system was low on refrigerant by looking through the sight glass. Basically if the refrigerant was sufficient, the sight glass would be clear without foaming or bubbles.

However ever since car manufacturers switched to R134a, the sight glass has lost its use. Because R134a behaves differently from R12. so even if you see foaming in the sight glass it does not mean refrigerant is low.

[Xulfiqar]

The sight glass is on top of the drier/receiver. For older systems using R12 refrigerant, you could tell if the system was low on refrigerant by looking through the sight glass. Basically if the refrigerant was sufficient, the sight glass would be clear without foaming or bubbles.

However ever since car manufacturers switched to R134a, the sight glass has lost its use. Because R134a behaves differently from R12. so even if you see foaming in the sight glass it does not mean refrigerant is low.

the sight glass is used differently in R134 systems, it bubbles for quite a while when the system is working correctly. Its more of an feel thing now, the best way to troubleshoot A/C systems be it R12 or R134 is to use an infrared temperature gun, A/C pressure gauges and measuring superheat and subcooling.

[ahsanonline]

My issues with the A/C are that it doesn't cool so much while car isn't moving. Once it gets moving it cools better. Also, while stationary if I rev the engine a little it starts to cool slightly better.

In hot weather it doesn't cool at all.

Condenser/evaporator etc are clean.

Any ideas?

[omkhan]

I guess your compressor is running heavy, taking load.

[cracked]

the signt glass on R-12 could exhibit same behavior while the system could be over charged as well as under charged..just google it and it said that the bubbles and foam on sight glass with R-12 dont only means its under charged.it could also mean system is over charged..my khyber has R-12 gas in it and i can see the foam and bubbles sometimes... but the ac tech put in 1 kg tin of R-12 gas in it..my question is if this meaning i have overcharged system or under charged??? the car showed high head pressure ,around 60..what should i do? mech said the compressor is weak..i wana know if it is actually the compressor before goin for the change-up... the coolin is ok-ish,,front two people dont sweat atleast

[ahsanonline]

the sight glass is used differently in R134 systems, it bubbles for quite a while when the system is working correctly. Its more of an feel thing now, the best way to troubleshoot A/C systems be it R12 or R134 is to use an infrared temperature gun, A/C pressure gauges and measuring superheat and subcooling.

The only way we get mechanics measuring anything are the A/C pressure readings.

Is there any pressure standard with regards to R134a? Do we measure the evaporator's intake air temperature and fill in gas accordingly?