Anyone had experience with the STV update kit?

[BamaWildcat]

I am pulling a complete air conditioning system off my parts car onto my project car. I have already checked the suction throttle valve (STV), and it does not hold vacuum.

I have been reading up on this valve, and it seems I have two options. One, buy the Year One STV rebuild kit, with a new diahragm, and O rings, and a clip, pictured below:

While this looks to be a decent solution, I have read elsewhere where something actually deforms inside the STV, rendering this a temporary fix until it gets warped along with the other goodies in the vavle.

The other option, which I have been studying heavily, is branded as an "update kit" which changes the system from an evaporative pressure system to a more modern thermostatic clutch cycling system. This is pictured below:

The thing is, I can find no real information about this unit. A lot of people sell it, and it is part number 50-2500P everywhere, but there is never a mention of who makes it. Above all, I would just like to read the manual that comes with it.

Has anyone tried this solution? What did you like/dislike? To me, I like the old system of the compressor staying on the whole time the A/C is on. While it is not efficient, it keeps you from playing with your carb getting your idle to work well with the system kicking on and off. But, if the choice is between cycling A/C and no A/C, it doesn't take much to make up my mind.

Please let me know if anyone can shed some light onto this kit.

Thanks!

[Guest 70 Electra]

You didn't mention the type of compressor or year/model of the car, but I'm assuming it is equipped with a continuously-running A6 compressor.

I'm no expert on this, but during the recent refurbishment of the system in my 70 Electra, I had an opportunity to discuss these "kits" with AC technicians and engineers at General Motors.

The unanimous opinion of everyone was that the A6 compressor's clutch was not designed to be repeatedly cycled on and off. While the compressor doesn't care about cycling, the clutch will have a very short life.

For what it's worth, I'd encourage you to seek OE type of components to return the functionality of your system to its original state. Then you'll have original appearance, functionality, and durability.

[NTX5467]

I concur . . . keep it original if you can. Changing it back from a "kit" can be more trouble than it's worth, all things considered.

On the later CCOT systems (as in my '77 Camaro and other pre-R-4 vehicles), the A6 DID cycle on an off as needed. If a new clutch is needed, be sure to change BOTH halves of it rather than just the "outer" part. With time and wear, there will be a wear pattern which both halves will mate to, but when you put a new outer part on that's smooth, it'll look like a sparkler under there every time the clutch engages. A '72 Pontiac shop manual I have said to cycle it on and off about 20 times to seat it in, but that didn't happen. Plus, you have to make sure the air gap between the halves is to spec.

As for the kit to change your existing system to a cycling system, the parts are pretty generic-brand items, it looks like. I suspect they are making a very nice profit on the "kit" too!

On the subject of "update kits", there's also a "POA Eliminator Valve" that's really a casting with holes for pressure switches to screw into, plus instructions on how to wire things and make other modifications. I found one Camaro parts vendor that billed it as a "POA Valve"--not a replacement item, but the real thing! Be VERY aware of what some of these vendors are trying to sell you if it's something of this nature! Other vendors correctly bill it as the "Eliminator Kit", though. See other threads re adjustable POA valves for low side pressure changes customized for R134a versus R-12.

Just some thoughts,

NTX5467