Yes, it is cycling on the low pressure switch.

 

If the register temps were Ice Cold then I would doubt that you are low on refergent at least low enough to cycle your low pressure cut out.

Is the compressor still running when the air warms up?
What speed is your blower set on?

It sounds like your evaporator might be freezing up; if your AC were only minimally cooling then I would look for a low charge.
If you do not have enough airflow through the evaporator it will cause this.

If I set my blower on Low and if I am on the freeway for any length of time where I am ramming air through the condenser, the temps will drop down near ZERO* and if there is any humidity it will start to blow slush out the vents.

You need to check and see if the compressor is running when the air is getting warm.

Do you have a set of gauge that you can check it with?

Here is what you are looking for, the Low pressure cutout on anything up to a 1991, after 1991.5 I do believe the switch changed to the opposite side of the block.

They might be interchangeable but I believe the switch will have interference with the blower housing so there must have been some minor changes.

The appropriate H-block is available at most auto parts.

The connector to the right of the blue hose was where the cycling switch was connected; I bypassed that circuit when I removed the cycling switch.



Here is a close up of the H-block and the Low Pressure cutout switch



This is the new block that I installed last year,

A word of CAUTION about the Low Pressure Switch, it is replaceable by simply unscrewing it from the block but DO NOT remove it with the system under pressure, there is NO Schrader valve behind it, removing the switch will discharge your entire system in a matter of seconds.

It has a machine thread and is sealed by an o-ring again this could be modified with a Schrader valve and then you could use a GM type switch.

If you have ever worked on most GM cars you will know that they can be replaced while the system is under pressure.

Maybe something I will do next time I have the system open.



This is your Receiver/ Dryer and accumulator and also has a sight glass on the top that you can look down into and see the liquid refergent, when you are using R-12, a fully charged system will be a solid stream of liquid however once you convert over to R-134 this feature can no longer be used because you only charge to 80%



Just thought you would like to see what the parts look like that we are talking about.
Jim

 

Wow, Jim thanks alot.

My dad put a can of R12 in it and now it works awesome, before it would be cold and then a loud click (compressor) and then it'd get warm, then cold again and i'd hear the comp. kick back in.

added a can and now it'll be good enough to sell it, it gets miserable here in the summer. Also, powerwashed the mud filled condenser.. that may have helped too.

I'm glad it was not a big problem.

 

Does the system need a charge to kick the compressor on?? Still haven't figured out why my compressor won't engage.. Did the paperclip trick and nothing.. Getting no juice down to the compressor..

 

the compressor will not kick on if it has no freon..... at least from my dad and I's past experience.

 

Hmm, maybe thats why it won't engage.. My uncle pressurized it with Nitrogen and made sure the system didn;t have any obvious leaks and before we recharged it, we wanted to make sure the compressor would engage.. But maybe it won't unless there is Freon like you said.. I do not have a clue, just glad the temps went back down!!

 

You don't need freon in there, just pressure. If it will not kick on with a charge of nitrogen you have pressure switch, wiring, or clutch troubles.