a/c cycling too quickly

[Levitan]

Last year, a/c went out on RollazX. She is an '90 or newer evidence 1.6 , 5 speed, lowered. Etc. Replaced the compressor after determining leaks were inside it. Recharged system to 21 lbs of 25 lbs (or whatever unit of measure is used for fake freon) per recommendation on here. Works great and cold. Problem, a/c cycles through to fast. Cold for 30 seconds, shuts off for 30 seconds.....and repeat. My mechanic says most cars have an adjuster to fix cycling problem. Do Festers have one? If not, how do I fix above situation?

Thanks in advance,
Dan "Levitan"

[htchbck]

I'm guessing by pounds you mean PSI on the low side? At what outside temp? Sounds like a low charge to me.

[FeistyFesti]

Oh my stars, I hope you didn't put in 21 pounds of refrigerant, that would blow up the midwest. I think it should only take 2.5 to 3 pounds, just an educated guess.

[Levitan]

Maybe psi is the correct term. I think specs are 25 Psi and from reading on here, 21 psi is optimal? I'm going from fuzzy memory.

[sc72]

Supper Model

How ya been Big Man, OOPS i mean Midwest supper Model, are ya back for the weekend?

[FB71]

Festiva A/C is a TXV system, it shouldn't cycle. If its kicking on and off, it most likely has a low charge. Can you get me the exact pressures while the compressor is running?

[htchbck]

Can you get me the exact pressures while the compressor is running?

Yeah, that is pretty important. I hadn't considered maybe you were measuring the pressure with the comp off (static pressure). With a proper charge I think its supposed to be around 25PSI on the suction (low) side, and around 220 on the high side, at around 80* ambient air temp. Higher for higher temps, lower for lower temps. If you're at 25PSI static though, then its the low pressure switch thats cycling it, as soon as the comp starts pulling freon through the system, the low side pressure drops and it cuts the comp.

[FB71]

R134a pressures are roughly 5-10 psi below refrigerant temp, ie; 30psi (low side, compressor running), roughly equals 35*-40*f refrigerant temp in the evaporator core. Any lower than 30psi will cause ice to form on the evaporator, stopping airflow and not cooling.

Low side should run 28-34psi, high side should run anywhere from 150-225psi, depending on ambient temp.

[htchbck]

R134a pressures are roughly 5-10 psi below refrigerant temp, ie; 30psi (low side, compressor running), roughly equals 35*-40*f refrigerant temp in the evaporator core. Any lower than 30psi will cause ice to form on the evaporator, stopping airflow and not cooling.

Low side should run 28-34psi, high side should run anywhere from 150-225psi, depending on ambient temp.

Dang I was close! Lol

[ericsmith32]

Festiva A/C is a TXV system, it shouldn't cycle. If its kicking on and off, it most likely has a low charge. Can you get me the exact pressures while the compressor is running?

So it's supposed to stay on all the time? What does it mean when snows starts flying out the vents?

[FB71]

A TXV system throttles the refrigerant flow into the evaporator. It may cycle in lower ambient temps, but current temps around the country should keep it running constantly. Frost from the vents means its running too cold, and it will freeze up the condensed water on the evaporator. There's several things that can cause low temps; bad TXV, bad de-icing switch, gross overcharge...

[ericsmith32]

It's probably overcharged although doesn't seem like it. I had to bypass the temp switch inside or it would shut it off. I'm usually able to throttle wear it doesn't happen. Sure does drip alot of water though.

[FB71]

It's probably overcharged although doesn't seem like it. I had to bypass the temp switch inside or it would shut it off. I'm usually able to throttle wear it doesn't happen. Sure does drip alot of water though.

ok... bypassing the de-icing switch is one of your problems! It shuts off because the evap is freezing. You need to find out why the evap is freezing.

[ericsmith32]

ok... bypassing the de-icing switch is one of your problems! It shuts off because the evap is freezing. You need to find out why the evap is freezing.

I was thinking it was the switch itself? Should pull one in a junkyard someday.. man that ac is nice though! Does seem to work fine but I shut it off every so often and run the outside air. The compressor is quiet but does draw down the engine alot but it's a auto.

[GenevaDirt]

I was thinking it was the switch itself? Should pull one in a junkyard someday.. man that ac is nice though! Does seem to work fine but I shut it off every so often and run the outside air. The compressor is quiet but does draw down the engine alot but it's a auto.

it may draw down the engine....but it does not affect the mileage. At least it did not on my trip to West Virginia. 32.6 running at 70 and better the whole there and back with the air running there and off on the way back. Just about the same average both ways....within a couple of tenths.