AC Cycle Switch for 1989 SHO after R134a Conversion

[DeepPower]

I bought a 4 seasons from local parts place!
part number 36676 4seasons

wont thread on all the way to receiver dryer that was replaced when I did new compressor liker 4 or so years ago... the one that did thread on not sure of brand but the 2 numbers on the bottom are 69360 and 0203 when I did a google search a ford vehicle r12 cycle switch came up! only reason I am replacing is cause switch is leaking from middle.... it drained whole system with in a few hours! cycle switch has been off for about 2 months and still has pressure in the system now !

Converted my 1989 SHO from R12 to R134a last year. Now, A/C is fully charged but compressor cycles rarely (usually off) and it's getting hot here in Texas.

I'm thinking I should try to replace the compressor cycling switch with the R134a switch, but I'm not sure what p/n. I thought Four Seasons 36676 would be the way to go, but after a forum search the above post says no (although I don't know what year SHO @christiansho has). There is also a Santech MT0613 that might be the correct p/n.

Any suggestions? I need to do this fast!

 

[LOUDSHO92]

We have the correct one here: SHO Source

The switch does help but your A/C should function without it.

 

[rubydist]

when it is hot out and the ac is properly charged, it will not cycle - it will run constantly. that is how it is supposed to work.

 

[DeepPower]

By cycles rarely, I mean the A/C is usually off.

@LoudSHO92, what is the advantage of the R134a switch after the conversion, over the R12 switch?

 

[LOUDSHO92]

By cycles rarely, I mean the A/C is usually off.

@LoudSHO92, what is the advantage of the R134a switch after the conversion, over the R12 switch?

It expands the operating pressure range for the R134a.

 

[jimtash]

Check the compressor clutch shim gap. Too wide and the clutch won't engage the pulley or sporadic at best. I recently converted as well and have no issues.

 

[DeepPower]

Check the compressor clutch shim gap. Too wide and the clutch won't engage the pulley or sporadic at best. I recently converted as well and have no issues.

Thanks, I'll check that.

Also, last night I bought the R12 AC cycle switch and I'll also install it today, so hopefully I'll have AC for Memorial Day weekend.

But here's a question I should have asked in the first place: how does the A/C cycle switch work? These are the specs for the cycling switches for my '89 (I took the Four Seasons 36676 p/n from christiansho's post):

Four Seasons 36676 (R134a)
Off Pressure (psi): 21 psi
On Pressure (psi): 42 psi

Santech MT0203 (R12)
Off Pressure (psi): 25 psi
On Pressure (psi): 45 psi

So I'm confused - the switch turns on and off based on the pressure in the accumulator, right? Does it turn off when the pressure drops below the off pressure, or above? Would my A/C be on or off at pressures 18psi, 30psi, 48psi?

 

[DeepPower]

O.K., checked the compressor clutch shim gap and it's fine. It's definitely the switch. But when I put in the Santech MT0203, which the book says is the direct replacement for the R12 switch, the threads are different and it won't screw in.

I found a bolt with the same thread pattern as the OEM sender and used it to check a Four Seasons 36676 at O'Reilly Auto. The threads on that one won't fit, either.

The system is slightly overcharged, and since the R12 switch is meant to handle lower pressure I need the R134a switch.

The OEM one has "9304" and "F3AH-" on it.

 

[rubydist]

The system is slightly overcharged, and since the R12 switch is meant to handle lower pressure I need the R134a switch.

In this you are incorrect. Since the system is slightly overcharged, the compressor will run longer, as though you had the other switch with the proper pressures in the system.

 

[DeepPower]

In this you are incorrect. Since the system is slightly overcharged, the compressor will run longer, as though you had the other switch with the proper pressures in the system.

I thought that, if the pressure is higher than the ON pressure, then the switch turns the compressor off to protect the system? Is that wrong?

 

[DeepPower]

Well, my car has a manufacturing date of December 1988. I'm thinking that there was some differences in the first '89 Tauruses off the assembly line.

 

[rubydist]

no, the cycling switch will turn off the compressor when the low side pressure gets below the set point. on the R12 systems, there was no high pressure cutout switch.

on the R134a systems, there is a high pressure switch on the high side that will turn off the compressor if the high side pressure gets too high.

 

[JRA2000TL]

I had an issue with buying the wrong switch for my 89 when I replaced everything. When I took it to the shop to have them vacuum and charge the system after my new components install, I had them replace the switch since it was cheap. I had the bought the wrong one, and I can't remember which one it was. Same issue you had--threads didn't match. It depends on which accumulator you buy. Both the pre 94 and post 94 ones will work, but the threads for the switch ARE different based on whichever one you buy. If you buy the older one meant for the R12 switch, it might require an adapter to for the 134a switch to fit correctly. That was probably my issue.

 

[DeepPower]

I had an issue with buying the wrong switch for my 89 when I replaced everything. When I took it to the shop to have them vacuum and charge the system after my new components install, I had them replace the switch since it was cheap. I had the bought the wrong one, and I can't remember which one it was. Same issue you had--threads didn't match. It depends on which accumulator you buy. Both the pre 94 and post 94 ones will work, but the threads for the switch ARE different based on whichever one you buy. If you buy the older one meant for the R12 switch, it might require an adapter to for the 134a switch to fit correctly. That was probably my issue.

What's the manufacturing date of your SHO (it's on the door pillar)?

So did you replace the accumulator? I have a brand new accumulator in my spare parts closet, and it fits all the switches that are supposed to fit the '89, meanwhile even the AutoZone R12 switches won't fit my OEM accumulator.

Where did you get the adapter - do you have a p/n?