Can I use an NOS a/c pressure switch with 134a?

[WH23G3G]

The aftermarket a/c low pressure switch I bought for my 73 Charger is wrong. I've got a brand new wiring harness from Year One for the a/c underhood and interior. I've got all new a/c parts and remade hoses. The connector on the new harness is side by side for horizontal terminals but the switch has side by side vertical terminals. So it won't plug in. I've got pictures of original 73 and 74 Chargers with the correct horizontal plug and switch. I can still get an NOS switch but is it safe to use with 134a since the pressures are a little different? I can't find an aftermarket switch that has the correct hookups.

[maxwellwedge]

I don't see why not. Will the pressure actually change with the different juice?

[WH23G3G]

I think the pressures are different between R-12 and R-134. I think R-134 has a much higher pressure. I'll ask some of the veteran mechanics at the shops I deliver to this week.

[Chatt69chgr]

Might call the folks at Classic Auto Air in florida and ask them.  They do conversions and sell the stuff to do it yourself, ie, convert from R12 to R134a.

[1BAD68]

The pressures are different but not significant enough to change the switch.

[Nacho-RT74]

Low pressure switch ( at dryer ) has nothing to do with performance on the system. Is teh same to any Gas you use, is simply a sensor to cut the power to clutch when you don't have gas on system. You can use either one you find.

[elacruze]

It's fine, the low pressure switch is only there to protect the compressor if you run low on refrigerant. by the time you hit the LPS you're pretty much out of gas anyway, whether r12 or r134a. Be sure that if it has an o-ring, you use a green one. Lube the o-rings and connectors with mineral oil.

[gtx6970]

As mentioned the LPS doesn't really care WHAT it reads , just so long as it reads something. just make sure you have a 134A compatibile O-ring and move on

[WH23G3G]

Ok I think I'm ok with the switch then. Now I'm worried about the o-ring kit. I don't see a 134a kit available anywhere. So I bought the universal green o-ring kit from the parts store. Eventhough several of them fit over the connectors. There are some that are thicker and some that are thinner but they both fit. They are measured in metric so I don't even know if I should use these o-rings.

[elacruze]

Don't overthink the o-rings either, pick one that's the same diameter or the closest smaller diameter, and the same thickness or the closest thicker one. Stuff it in and go. If it's too big to work, you'll know it when you try it. You can't hurt anything there.

<edit> The switch did come with black o-rings to compare with, didn't it? Even if it did not, just pick one that fits comfortably on the fitting and appears thick enough. The low side of the system rarely ever has to endure more than about 100psi so you don't need NASA spec parts in there. After you've assembled it, whoever charges the system should have a sniffer to verify that the seal is secure.