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...charged to manual volume.
What manual? What charge does it say?
I charged it to the tag under the hood by weight.
What weight does the tag show?
Hooked up gages and everything normal...
What gauge readings do you consider normal?
...and was forming ice on both ends of cold line.
That's not normal, and it proves that the low-side pressure is dropping low enough for the temperature to be well below 32°F.
Gages read low 25, high 175, ambient about 75 deg.
That's on the verge of too low for the clutch to stay engaged, if the low-pressure switch is adjusted properly. This shows the correct pressure settings for each refrigerant, so ignore the first one for R12:

(click this text)


This shows how to adjust the low switch, but it's written for R12, so ignore the pressure given here:

(click this text)
Is there a temp sensor...?
No.
Is there an internal valve in compressor that could cause this?
No.

This page shows & explains how to install an R134a system in these trucks:

(click this text)
 

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It was turning off on the high pressure sensor. ...another grenaded pump. No reason I can think of why the pump went out. ... Please let me know if I missed anything obvious?
The obvious answer is that it had too much refrigerant (overcharged) which naturally led to liquid entering the compressor, which hydraulic'ed it, just like water going into the engine would do. This is why refrigerant work should be left to pros. If you make even a small mistake, you can grenade the compressor, which then puts shrapnel through the manifold hose & into the condenser, which cannot be reliably cleaned, so it has to be replaced at the same time as the compressor, orifice, refrigerant, & oil.

Take it to a pro.
 
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