Can you accurately charge a system........

[Stresst]

Can you accurately charge a system w/o knowing how much freon? My truck is in the shop nearing completion and when I asked how much freon he put in he said he doesnt know that he did it by monitoring the pressure. He agreed with me that he couldnt find a definitive answer as to how much freon this truck holds......WTF?

I sure hope when I pick it up its blowing nice and cold, today is supposed to be the hottest day of the year thus far.

 

[retorq]

Most at home guys that refill for the summer just go by pressure ...

 

[Stresst]

Most at home guys that refill for the summer just go by pressure ...

First he said he couldn't determine actual capacity. ( fine, neither could I ) But then he said he is doing it this way for 12 years since 134 came out......yada yada yada.

 

[fire730]

There is a sticker under every cars hood somewhere that tells the system capacity. Alot of stickers are not readable or missing but they were there at one point. It's nice to have that capacity as a baseline because an overcharged 134a system will not work properly.

But unless you have a high dollar AC charging machine that injects the freon according to what you tell it to put in you basically just charge it according to your gauge readings. Although it's not an exact science any competent mechanic can charge a system by system pressures. HTH.

 

[Stresst]

There is a sticker under every cars hood somewhere that tells the system capacity. Alot of stickers are not readable or missing but they were there at one point. It's nice to have that capacity as a baseline because an overcharged 134a system will not work properly.

But unless you have a high dollar AC charging machine that injects the freon according to what you tell it to put in you basically just charge it according to your gauge readings. Although it's not an exact science any competent mechanic can charge a system by system pressures. HTH.

When I went to a particluar shop (pep boys) for a second opinion he mentioned there was no way to tell how much was in there and that he needed to evacuate, weigh and put it back. I remember he showed me there was 2.9lbs and that he put back 2.75. The machine read 2.75 complete when it was done.

I was just curious my issue is how does he know if there is a restriction somewhere charging based on pressures.....I dont know just throwing it out there....

 

[fire730]

Also another good indication of the system being charged properly is after running for a while you want the low side (the bigger line) to be sweating and very cold to the touch all the way from the accumulator to the compressor.

---------- Post added at 10:43 AM ---------- Previous post was at 10:38 AM ----------

What did you have done to the AC system?

As far as weighing out the freon it depends on what you are charging from. A 12oz can or a 30 lb cylinder.

 

[Stresst]

Also another good indication of the system being charged properly is after running for a while you want the low side (the bigger line) to be sweating and very cold to the touch all the way from the accumulator to the compressor.

---------- Post added at 10:43 AM ---------- Previous post was at 10:38 AM ----------

What did you have done to the AC system?

As far as weighing out the freon it depends on what you are charging from. A 12oz can or a 30 lb cylinder.

I replaced the main hose, condenser,y-pipe, accumulator, orifice, hoses that run front to rear, expansion valve, rear evaporator, compressor, hi and low side switches, heater bypass valve, fan clutch, added an electric pusher. Pretty much everything except the front evaporator which I cleaned the heck out of.

Hopefully when I get the truck back tonite everything is ok.

---------- Post added at 12:36 PM ---------- Previous post was at 12:13 PM ----------

There is a sticker under every cars hood somewhere that tells the system capacity. Alot of stickers are not readable or missing but they were there at one point. It's nice to have that capacity as a baseline because an overcharged 134a system will not work properly.
HTH.

I wish I can hear it from someone directly whom has charged a Tahoe/Escalade/Yukon with rear air themselves a few times and can tell me exactly how much it takes for sure. Some have said the label is inaccurate on rear air trucks that they take more then 2.75lbs gm recommends, one guys said he put 3.5lbs in his aunts truck, tech choice parts site listed 4lbs but I emailed them and they actually said its 3.5lbs (from Mitchels) while alldata and chilton say 2.75

Ehh, let me get the truck back and see what happens. Im almost setting myself up for a dissapointment!

Hopefully everything will be good.

 

[SunlitComet]

Can you accurately charge a system w/o knowing how much freon? My truck is in the shop nearing completion and when I asked how much freon he put in he said he doesnt know that he did it by monitoring the pressure. He agreed with me that he couldnt find a definitive answer as to how much freon this truck holds......WTF?

I sure hope when I pick it up its blowing nice and cold, today is supposed to be the hottest day of the year thus far.

it is possible and pressures and temperatures should be used to fine tune the charge. That's one of the purposes of the performance charts.

 

[taylorjm]

I would rather someone that uses gauges vs weight work on my vehicle. When someone says they want to drain the system and put in the right amount by weight, it makes me think they haven't done it enough to know how to use a set of gauges. The gauges can tell you a lot about the system and how it's working. I'd rather someone be gauging it than just say "well I put the right amount in, I don't know why it's not working".

 

[Stresst]

I would rather someone that uses gauges vs weight work on my vehicle. When someone says they want to drain the system and put in the right amount by weight, it makes me think they haven't done it enough to know how to use a set of gauges. The gauges can tell you a lot about the system and how it's working. I'd rather someone be gauging it than just say "well I put the right amount in, I don't know why it's not working".

WOW, ok. Makes sense now that I think of it.