Question about a/c pressure readings

[someday31]

I get 29 on the low side, 115 on the high running at idle. The refrigerant line is cold under the hood, compressor comes on! So could it just be my blend door? Compressor maybe....would think my high side would be higher? It was about 77 degrees. Any thoughts? I know you guys know your cars here so know you can help. Thanks.

[j cAT]

Originally Posted by someday31

I get 29 on the low side, 115 on the high running at idle. The refrigerant line is cold under the hood, compressor comes on! So could it just be my blend door? Compressor maybe....would think my high side would be higher? It was about 77 degrees. Any thoughts? I know you guys know your cars here so know you can help. Thanks.

the low side with r134 is normally around 40-50psi ...@1200 rpm

75-85 deg f ..high side should be 280 psi I've seen 330 psi depends on how hot out and condition of the system...charge...

115psi on high side I would check your gauges ..cannnot not be that low..lowest is around 225psi ...

[someday31]

The gauges I bought are Yellow Jacket professional gauges they are a week old and I paid good money these. Maybe I am reading my gauges wrong.... this is a gauge that reads 12/22/134a... on the 134a scale I get 115 on the high side...but then theres a scale thats on the outermost of the gauges and doesnt specify refrigerant, just says psi... that shows about 148psi. Hope that helps to clarify?

Originally Posted by j cAT

the low side with r134 is normally around 40-50psi ...@1200 rpm

75-85 deg f ..high side should be 280 psi I've seen 330 psi depends on how hot out and condition of the system...charge...

115psi on high side I would check your gauges ..cannnot not be that low..lowest is around 225psi ...

[j cAT]

Originally Posted by someday31

The gauges I bought are Yellow Jacket professional gauges they are a week old and I paid good money these. Maybe I am reading my gauges wrong.... this is a gauge that reads 12/22/134a... on the 134a scale I get 115 on the high side...but then theres a scale thats on the outermost of the gauges and doesnt specify refrigerant, just says psi... that shows about 148psi. Hope that helps to clarify?

these guages are a manifold charging set..? the valves on the ends should be closed..if open pressure can flow from high side to low reducing pressure..

like I said 115 psi is not correct ...

[someday31]

Originally Posted by j cAT

these guages are a manifold charging set..? the valves on the ends should be closed..if open pressure can flow from high side to low reducing pressure..

like I said 115 psi is not correct ...

Yes they are a charging set, and the valves were closed. So my readings being what they are, what does that mean? Restricted?

[j cAT]

Originally Posted by someday31

Yes they are a charging set, and the valves were closed. So my readings being what they are, what does that mean? Restricted?

use the pressure readings on the outer edge of guage..I would say you are a little low on refrigerent with the 148psi on the high side...

when you add refrigerent you will see a rapid rise in pressure when you begin to approach the maximum amount of refrigerent that is the systems capacity...I would look to get that pressure to around 200psi..see how it runs @80deg F air temp...

it is best to start with the system empty then install the correct amount. this way you know that it is charged correctly . then with the engine at 1200 rpm record the pressures hi/low and the air temp..

then at another time , when you check your system you will have a good indication of the systems charge or proper operation...

also measure the temp of the air blowing out the interior vents..

only connect/disconnect the high side guage with the ac OFF...after pressure has droped..

[MT-2500]

Originally Posted by someday31

Yes they are a charging set, and the valves were closed. So my readings being what they are, what does that mean? Restricted?

As said high side is low.
We need the gauge readings at idle and at 2K with engine warm and compressor running.
Gauge reading should change with compressor running and compressor cycling off when low side drops below cutoff pressure.
Post back all pressure readings low and high side.

[someday31]

Here are pics of my gauges! I get 115 on blue 134a scale at idle, second row in...... what does the outer psi scale show/mean? I wont be at the car till Sunday to see what I get at 2,000 rpm.
I pulled a vacuum 525microns for 45 minutes and then filled....I add 12 ozs of refrigerant and then stopped since there was no change in air temp. I put a dig a/c thermometer in the vents and got 77 degrees.

Originally Posted by j cAT

use the pressure readings on the outer edge of guage..I would say you are a little low on refrigerent with the 148psi on the high side...

when you add refrigerent you will see a rapid rise in pressure when you begin to approach the maximum amount of refrigerent that is the systems capacity...I would look to get that pressure to around 200psi..see how it runs @80deg F air temp...

it is best to start with the system empty then install the correct amount. this way you know that it is charged correctly . then with the engine at 1200 rpm record the pressures hi/low and the air temp..

then at another time , when you check your system you will have a good indication of the systems charge or proper operation...

also measure the temp of the air blowing out the interior vents..

only connect/disconnect the high side guage with the ac OFF...after pressure has droped..

[j cAT]

Originally Posted by someday31

Here are pics of my gauges! I get 115 on blue 134a scale at idle, second row in...... what does the outer psi scale show/mean? I wont be at the car till Sunday to see what I get at 2,000 rpm.
I pulled a vacuum 525microns for 45 minutes and then filled....I add 12 ozs of refrigerant and then stopped since there was no change in air temp. I put a dig a/c thermometer in the vents and got 77 degrees.

the pressure is the outer red area, this would be about 150psi ..disrgard the inner guage refrigerent marks...

you installed 12 oz. of r134 you need more refrgerent should be around 32 oz.or a little more ,,, make sure you only install what your capacity is NO MORE !

as you install the refrigerent monitor the high side pressure ...then you will notice the air temp drop when the pressure rises...it is the change in pressure from high to low that causes the cooling of air [the absorbstion of heat from air ].....with low pressures on high side you can not get cool air ...

[someday31]

Originally Posted by j cAT

the pressure is the outer red area, this would be about 150psi ..disrgard the inner guage refrigerent marks...

you installed 12 oz. of r134 you need more refrgerent should be around 32 oz.or a little more ,,, make sure you only install what your capacity is NO MORE !

as you install the refrigerent monitor the high side pressure ...then you will notice the air temp drop when the pressure rises...it is the change in pressure from high to low that causes the cooling of air [the absorbstion of heat from air ].....with low pressures on high side you can not get cool air ...

Ok, thanks, I will add the rest of refrigerant and hope for cold air! The system says it takes 2.0lbs. I just was confused when my low side lines were cold/sweating but inside the car it wasnt cold at all, so I didnt go further and add anymore refrigerant.
My initial problem was that the compressor was cycling on and off but I wasnt low on refrigerant. But the system had been opened for other work, for over 2 weeks and then just refilled with no vacuum so that may have created excessive air or system causing the compressor to cycle on and off. I will finish the fill up Sunday and see how it goes! Thanks again.

[j cAT]

you vacuumed the system and the vacuum held at 500microns this is good...now with the air removed you should get , with the proper refrigerent install a very good cooling ....

what you saw on those lines getting very cold, but no cold air coming out is because the evaporator was only cold on the supply end ....not the complete evaporator coil length ...many times with a low charge ice can build up there , but little cooling of the air ..this was very common with the R12 refrigerent which did work much better ...too bad it eats up the atmosphere , R12 works much better..


post back with how it all works ..

[someday31]

Originally Posted by j cAT

you vacuumed the system and the vacuum held at 500microns this is good...now with the air removed you should get , with the proper refrigerent install a very good cooling ....

what you saw on those lines getting very cold, but no cold air coming out is because the evaporator was only cold on the supply end ....not the complete evaporator coil length ...many times with a low charge ice can build up there , but little cooling of the air ..this was very common with the R12 refrigerent which did work much better ...too bad it eats up the atmosphere , R12 works much better..


post back with how it all works ..

Hey was just curious....I just picked up a 30lb sealed cylinder of R134a for $150 cash.....is that a deal?

[MT-2500]

Originally Posted by someday31

Hey was just curious....I just picked up a 30lb sealed cylinder of R134a for $150 cash.....is that a deal?

A good deal for the seller.
And always make sure it is the good pure stuff.
And be sure to have a good set of scales to weigh what you are putting in.

I get a lot of 30 lb. kegs for 79.95 US $ sometimes 89.95$

[someday31]

Originally Posted by MT-2500

A good deal for the seller.
And always make sure it is the good pure stuff.
And be sure to have a good set of scales to weigh what you are putting in.

I get a lot of 30 lb. kegs for 79.95 US $ sometimes 89.95$

Wow! Where do you get them for that price? Maybe because I'm in NY it's expensive?

[MT-2500]

Carquest and O'rielly and Auto zone.
Always watch for specials on it.

Yes NY may have a higher market.