I made one "good" R4 compressor from 2 that I have. Before I install it, I wanted to set up a "bench" test so I do't waste more of my time if it's no good from the get go.

The battery charger is to engage the clutch. I have a compression gauge shoved into the pressure side of the R4. I put in 2 oz of mineral oil and swashed it around. The motor is 1/2 HP and the motor is mounted to the plank of wood but the R4 is tensioned by hand. It definitely puts out pressure but I couldn't measure how much because the motor does not have enough torque. The compression gauge blows off when the R4 is spinning but if I push it in to stop it from blowing off the motor can't keep up and stalls. Anyone know how many HP the R4 needs? Anyway. I tried and will not go any further with the test like getting a bigger motor and mounting the R4 with an adjustable tensioner bracket.
I have a good feeling this R4 will be OK so will install it when I have time, check the system for leaks and if none, flush, evacute and charge with Envirosafe ES12A unless I come upon some R12 real soon.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
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