A/C question MT2500

[laxman21]

Anyone have the shop manual that has the pressure reading for a 99 blazer? Low and high side.

[MT-2500]

Originally Posted by laxman21

Anyone have the shop manual that has the pressure reading for a 99 blazer? Low and high side.

The pressure readings will vary.
Outside tempt and air flowing threw the condenser and rad has a big affect on the high side readings.

Good low side will range from 28 to 35 lbs while the compressor is running.

Good high side readings will range from under 200 to 350 lbs depending on tempt and air flow threw condenser.

You need to take readings at idle and at 2000 rpm with compressor running.

The low side pressure will run close to vent output tempt.

For ever lb of low side pressure = 1 degree evaporator tempt.
30 lbs low side should put 30 degrees out put from evaporator.
And give you around 35-40 degrees vent tempt.

[laxman21]

Originally Posted by MT-2500

The pressure readings will vary.
Outside tempt and air flowing threw the condenser and rad has a big affect on the high side readings.

Good low side will range from 28 to 35 lbs while the compressor is running.

Good high side readings will range from under 200 to 350 lbs depending on tempt and air flow threw condenser.

You need to take readings at idle and at 2000 rpm with compressor running.

The low side pressure will run close to vent output tempt.

For ever lb of low side pressure = 1 degree evaporator tempt.
30 lbs low side should put 30 degrees out put from evaporator.
And give you around 35-40 degrees vent tempt.

HMMMM.

at idle

78* outside

Compressor would kick on at 50LBS low and 105 high

Shut off at 24 and 145 high

vent temp at 54


What about a suburban?

45 low and 200 high the whole time...never shut off

52* at vent

[MT-2500]

On the Blazer if it is cycling on and off very much You are low on R-134a.
And vent tempt is a little high.
I would pump it down and run a Vacuum on it and recharge with the set charge.
Also the low side turn off is boder line low with a 24 lb kick off .
You need to have the turn off closer to 28-30 lbs.
The evaporaor will freeze up at 24-25 lbs.

On the suburban you may have expansion valve/orfice tube problems.
Does it have rear air?

For good cold air you need to keep the low side around 28-30 lbs.
MT.

[laxman21]

Originally Posted by MT-2500

On the Blazer if it is cycling on and off very much You are low on R-134a.
And vent tempt is a little high.
I would pump it down and run a Vacuum on it and recharge with the set charge.
Also the low side turn off is boder line low with a 24 lb kick off .
You need to have the turn off closer to 28-30 lbs.
The evaporaor will freeze up at 24-25 lbs.

On the suburban you may have expansion valve/orfice tube problems.
Does it have rear air?

For good cold air you need to keep the low side around 28-30 lbs.
MT.

THe burb has rear air.

[MT-2500]

Originally Posted by laxman21

THe burb has rear air.

If you can find a place to do it pinch off a hose on rear air and see if pressure gets better.
If so the expansion valve on rear unit is bad.
MT