Question on cycle switch

[Jason94sport]

94 X.

According to the book I have, the cycle switch is supposed to cycle below 24PSI.

The pressure has never gotten that low since I had my ac worked on. It has been way hot & humid & don't expect it to decrease here till November.

I did a few tests & I get power form 1 wire from the cycle switch harness but not the other. When I loop the wires direct to the compressor I get power from each wire. I was using a test light. A ford guy I know said that the wiring may have a short. How accurate is this info? Am I even testing this thing right? What would be the problems if the compressor never cycled? I haven't heard it cycle since I had the work done.(entire summer) The entire AC system was replaced.

My normal driving low side is 36PSi & the high is about 290. This is while driving(ran gauges in car while driving) Climbs to about 42 & 310 when idle.(but again is very hot & humid in south FL 24/7)

Thanks

 

[ma96782]

Try bringing the idle speed up to 1500 RPM......when you're looking for the functioning of the switch. BTW a new switch isn't that expensive.

Not to mention, the wires or connection block. My Chevy wasn't working, and I traced it back to a bad connection block at the switch......that when wiggled........would only work sometimes.

Aloha, Mark

 

[Jason94sport]

The switch is new, & there's no change at any rpm. The compressor does not cycle. But as I read, it won't above 24psi & the gauges have not gotten that low.
The wires run from the switch harness to somewhere in a harness that looks to go into the interior.

 

[TheJackal]

It seems to me, that if the compressor doesn't come on, you wouldn't have good pressure in the system. 42 seems a little high, at least IMHO. But if the switch is only supposed to turn on the compressor if the pressure is 24 PSI, and it's not getting that low, then it sounds like it's doing its job.

You'll need to let the vehicle sit for a while (turned off) and check the pressure. After it stabilizes and the pressure is below 24 PSI, start it up and see if the compressor comes on.

Does the A/C blow cold air?

 

[Jason94sport]

Oh yeah the AC is fine. That's not it. I just noticed the compressor is not cycling. Or least I haven't seen it. Meaning the compressor is always on & the clutch has not disengaged. Was looking for a confirm on how to test it correctly & what PSI it should disengage the compressor.

 

[TheJackal]

Ah, I see.
Well if the switch has been replaced and it still isn't right than it could be a short circuit.

You don't want the compressor to run all the time like that. You'll not only overpressurize the system, but all that running will eventually wear out the compressor quickly. I'll have to look up some info about this but got to run right now.

 

[ma96782]

I assume that you didn't overfill it???

Shamaal said:

The switch on the accumulator controls the clutch on the compressor. When the system pressure is less than 24.5 psi the clutch is disengaged. When the pressure is greater than 43.5 psi the compressor clutch engages. The switch is screwed on to a schraeder valve, like on tires. It can be removed without discharging system, having said that there have been two instances this season of sticking valves. Running the compressor (jumpering) without oil for >30 seconds can damage it.

And......V8BoatBuilder said:

Interesting A/C Info from the Ford Factory CD-ROM

The A/C clutch is controlled by the A/C cycling switch (19E561) and the A/C pressure cut-off switch, which are connected in series. The A/C cycling switch is mounted on the suction accumulator/drier (19C836), and the A/C pressure cut-off switch is mounted in the discharge line at the A/C condenser.

The A/C cycling switch closes when the pressure on the low side of the system reaches approximately 276-324 kPa (40-47 psi). The A/C cycling switch opens when the pressure drops to approximately 163-175 kPa (23.5-25.5 psi), disengaging the A/C clutch. In ambient temperatures below -1º C (30º F), the A/C cycling switch will not allow compressor operation because of low system pressures.

The A/C pressure cut-off switch is used to interrupt A/C clutch operation in the event of high system discharge pressures. The A/C pressure cut-off switch is a single-function switch that controls A/C clutch engagement. When compressor head pressures rise to approximately 2896 kPa (420 psi), the contacts open, disengaging the A/C clutch. When the pressures drop to approximately 1724 kPa (250 psi), the contacts close to allow A/C clutch operation.

The pressure you are seeing may have something to do with the current ambient air temps you are having over there in FL.......see chart.......

System pressure/air temps chart

http://www.autoacforum.com/aacf/ptchart.cfm

And......IF it won't shut off.......

AC Clutch won’t shut off:

Juice to the compressor is controlled by a relay which is driven (grounded) by the PCM. The low pressure switch sends a voltage signal to that Relay. When the contacts are open, there shouldn't be any voltage on the output side of the switch. Take your meter and probe both sides of the harness. Lt Green seems to always be the input and Blue or White (or whatever the line felt looked good the day it was built) the Relay signal. If you find voltage on both, there's a short between the Pins or that output is picking up voltage from somewhere else. If no volts, you can spend 9 Bucks on a new relay, but you might remove it first and see if the compressor continues to run. If it does, the clutch wiring is shorted to a voltage source.

Aloha, Mark

 

[Jason94sport]

ma96782 thanks for the info. I'll have to check the wires out with my meter.


I'm pretty sure the clutch is not cycling. Last night I took a all HW trip 30 miles up & 30 miles down. On the trip back it was 11pm so the air temp was in the high 70's. I had the AC on the 2nd air speed, normal mode. When I got off the HW there was very little air coming out of the vents. I switched to high & max AC & still very little air. Something froze up I guess. I got home, & let the X sit for 30 minutes started it back up & the AC was normal again.

The AC is charged correctly. I also do not have any blower motor or blend door problems.

 

[Jason94sport]

Bad cycle switch is seems. Damn cheap autozone replacements! I got 1 from NAPA & it's good now.

 

[ma96782]

Good to hear you got it fixed.

Aloha, Mark