91 Ford Bronco 351 Air Conditioner Question

Ok, I know there are a million and one questions and answers on A/C Service, but here is one more. The Bronco has been converted over to R134a and now the compressor clutch cycles for 5 seconds on/10 seconds
off. Putting a gauge on the low pressure side I get about 30 psi the slowly rises to 40 psi then the pump cycles pulling it back to 30 psi. There is very little cooling from the vents. The low pressure cycling switch has been changed to the 134a.
What should I look at next for trouble shooting the system.
Thanks
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net snipped-for-privacy@hotmail.com wrote:

Not far off on the pressure readings, but the low side shutoff could be a little lower, say 22~25 psi. If the accumulator (receiver/dryer) is getting cold & wet, the problem is most likely under the dash with the BDA (Blend Door Actuator).
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Yeah... didnt mention that, did I! SKC is right... cold accum is first thing to look for. If it's cold it's good. And the air blend is the problem.
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Well, tomorrow I should have some more information, I know that the evaporator is not getting very cold, no condensation on the accumulator either. But I should have a good set of gauges tonight to get good accurate numbers both low and hi.
Thanks again.
Backyard Mechanic wrote:

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net snipped-for-privacy@hotmail.com wrote:

It's hard to tell without looking at high side pressures.
If the conversion was done by a competent shop or tech or even me, the reading would indicate low charge.
But if the accumulator wasnt changed and the system wasnt properly evacuated first, it may indicate contamination. Usually the orifice clogged by mix of incompatible oils, which would be indicated by high pressures (high side) before the orifice tube.
If you want to roll some dice, dump in another can of 134a and wait for the compressor or high side hose to blow.
How much 134 did you put in, and how much R12 does it call for.. 134A capacity should be 80% of R12.
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