This is a '98 GMC - r134a, same as vette '94 and later.

This is the paper clip trick. Use it to tell if your low pressure switch is bad. It will also tell you if you have a clogged orifice filter (resulting in the switch shutting off power to the compressor).

 

This is static pressure; motor off.

The Mickey Mouse guage is only for relative measurements. Don't count on the numbers on the guage, just the before and after measurements.

 

This is the pressure with the motor running, A/C max'ed before adding a can of 134a.

FIYF&*^KGJITY&T*&^ reflection!

The needle was just barely into the blue - see another pic of the guage next post.

Then add a can of chill.

 

The after-a-can measurement was at the top of the blue.

Here's another pic of the guage.

 

Then I measured again static - motor off. Doesn't really tell ya' much, unless there's a major problem.

Mine has a slow leak. The orifice filter is new, so I know that is not a problem. The switch The thingmobob that you jumped) was also replaced last year.

Make sure the guage is screwed on tightly before attaching to the valve.

Make sure the piercing pin us unscrewed - backed out - before screwing it onto the new can.

Don't remove the guage, or the empty can, from the hose with the hose still attached to the fitting.

 

Thanks...you are very helpful and knowledgeable. Pics shows me what the pressure switch looks like. My A/C clutch will not engage. Seems to be no voltage going to the clutch I will try this first. I'm new at this , please tell me which contacts to use the paper clip.

Hank

 

I'm not sure where the switch is on a vette there Hank.

Some one else here I'm sure will chime in...

It will be somewhere attached to the line itself, or a component on the line. Just look for a wire connector, and pull it. If it's a 3 wire, you',, have to determine which is a ground, and which is power. It's not complicated tho'...

 

....just HOW will the "paper clip trick" tell you if the orifice TUBE is clogged????...

....you would have to have the system in operation and observe readings on gauges on the liquid and suction sides in part, to determine that - just short of visually looking at the orifice TUBE itself and that could only be accomplished with removal of the tube itself!...if the tube was clogged it still would be hard to determine where the problem is located as you could have a "clog" in the condenser giving you generally the same symptoms.....

 

It COULD mean the tube is clogged.

If you think I should delete pics and text, just lemme' know.

 

....nah, just do what ya hafta do.....

 

Okay, so I recharged my system and it is blowing ice cold, but is it okay to have ice/frost form on the low pressure line from the accumulator to the blower box?

 

...whom are you asking?....uh, i don't even see you in this thread....

 

either of you two...I used schrade's method to recharge the A/C and it works perfect, I just wanted to see if frost on the lines was acceptable.

 

..well, it's his thread so, let's put him up to bat.....

 

I don't know about frost? but as I understand AC symptoms...When the bare aluminum low-side tubing at the accumulator to the compressor is sweating like a cold pop can it's indicating a correctly filled AC., However no sweating should be evident on the compressor itself as this will indicate an overcharge of the system, which can lead to possible Dangerous high pressure in the system.

 

..i was still waiting to find out EXACTLY how much his system was charged was as opposed to what it says the system takes...

94fla vette, ck your pm's.....

 

The only way to tell if anything is wrong is with a manifold gage set - I don't know how something with a "blue" area inscribed into the dial can compensate or tell you anything when pressure is dependent upon the temp of the air blowing across the condensor. Seems to me that's a good way to blow something up - especially if that blue turns red when the temp climbs.

Jumpering the low pressure switch harness contacts verifies that the circuit is intact but without knowing pressures, you could damage something - especially if there's not enough gas in it to carry the oil charge.

If the orifice is plugged up, your high will be too high; and the low too low. There are plenty of charts available to give you where they should be. Most restrictions, if severe enough, simply cause the compressor to cycle excessively (more than 8 times per minute at 70 degrees). Since the evaporator isn't getting a full shot of gas, what gets in flashes off immediately and there's no oomph left when it reaches the low pressure switch.


The low pressure switch should cut power to the compressor when the pressure is low enough to cause the Evaporator and suction line to ice over. Ice is created when the liquid refrigerant boils below freezing. If you're seeing ice, then something is probably wrong with the switch. Check it out by putting the system on high and pulling the blower motor connector. The low side will drop and the low pressure contacts should open cutting power. Note that pressure on your Low Pressure Gage. For R134, it should be 22.5 psi; for R12, 25 psi. Some switches are adjustable. Turn the screw between the terminals (if they exist) counterclockwise to lower the threshold; clockwise to raise it. Make your adjustments 1/2 turn at a time and retest.

If the pressures look normal, but it's making ice, something else is going on - probably a combo of refigerants. Those unlike mixtures fractionate and cause a host of funky problems. Hard to guess without knowing what the pressures are but if you simply dumped in some R134 or anything that is different on top of the original charge, it's time to start over.

 

Well I am taking mine in to my mechanic tomorrow and let him mess with it, it is too damned hot here. My blower works, the compressore engages, so I guess I have a leak and all the refrig leaked out. I think it must be a good size because I thinked it worked in the winter (defrost) and definatly worked last summer. So I want the leak found and repaired; don't want to have to keep throwing refrigerant at it every few months.

Thanks for the pics and write up!

 

If I remember, there is a charge psi somewhere printed on the system. Am I dreaming or does this exists. I remember getting the high side pressure number for my car somewhere.

 

"94flavette"...check your pm's