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Expansion Valve Adjustment on Dodge Van After Switching to R-134a

Hello,

This past weekend I converted my '84 B250 Dodge Van from R-12 to R-134a. I rebuilt the compressor using R-134a compatible seals, replaced the receiver/dryer, changed the oil, installed the proper fittings, pulled a vacuum, etc. I used 75% (by weight) of the regular R-12 charge. The manifold readings were 165 PSI and 35 PSI (high/low) with an ambient air temp of 82 degrees.

The system seems to be cooling fine now. The only difference that I noticed is that the compressor seems to be cycling on and off more rapidly than when it had R-12. I have heard that sometimes the expansion valve need to be adjusted after changing to R-134a. Is it possible to adjust the expansion valve on these vehicles and if so, what is the proper procedure? Thank you.

Reply to
T.C. Mann
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Because...?

Don't see a parallel-flow condenser on this list. Means you will never get really good system performance. It'll never come up to the level of a properly-functioning R12 system in the same vehicle, especially in high demand situations (slow speed, hot days). On the other hand, if you don't make high demands of your A/C system, perhaps your threshhold of "acceptable" cooling is less stringent than mine.

At what engine RPM? 165 on the high side is low.

No such adjustment is possible.

Reply to
Daniel J. Stern

Reply to
tim bur

the TEV or TXV more than likely needs adjustment when changing refrigerants. You may also need to change the thermostatic charge element. ( the bulb and diaphragm assembly ) You could check superheat and subcooling figures to figure out if the system is charged and the TXV is working correctly. I have no idea what those figures would be for an automotive system or if a replacement element is even available. To learn more about TXVs go to

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- on the other hand if it has acceptable cooling and the pressures are not too high, leave it alone and enjoy life.

mark

I have heard that sometimes the

Reply to
Mark

This can *sometimes* be done on stationary installations -- TXV adjustment and thermostatic charge element replacements are not possible on MVAC, at least not on this system.

Reply to
Daniel J. Stern

Reply to
Mark

Reply to
tim bur

And I would add "not necessary." The required operating ranges for both R-12 and R-134a are well within the operating range of the TXV, so it just does its thing and doesn't care which refrigerant is flowing through it.

Reply to
Steve

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