Old refrigerated glass case

[fix_it_man74]

Andy may remember this....I am trying to repair an old glass display case that was given to a friend, the comp runs for 10 - 15 seconds then shuts down for 30 sec to 1 minute and starts again for 10 - 15 sec............orig the condenser fan was burned so i replaced it, the fan runs fine now...... I was told to check the start capacitor, and the klixon switch so I replaced both, someone else said it may be the high low pressure switch, how do I check this? Oh when the comp is running the ***** in the sight glass looks fine. My friend had a so called refrigeration guy look at it and he said the comp was shot and to replace the entire condenser part of the system....duhhhhh..... Can you help or am I just pissin in the wind????

[Dan]

Is this a gravity coil service meat case? If so, the load will be very small. It is possible that the unit is oversized. What size is the condensing unit? Model number or electrical characteristics such as RLA would help. Do you have gauges? The way to check the low pressure switch is with a voltmeter. Put the probes on each side of the switch and check for voltage. If there is no voltage reading after the compressor turns off, then the low pressure switch is not causing it. If you read voltage when the compressor turns off, then the low pressure switch is opening and causing the compressor to turn off.

Is the case refrigerating or not?

[monkey spanners]

Does the condenser fan cycle on and off with the compressor, if so you need to find what is causing this (trace the wires back until you get to a pressure switch or stat). If its a pressure switch you need to fit some gauges to see whats going on. If its just the compressor cycling with the condenser fan staying on it sounds like the compressor is cycling on the klixon (bimetalic switch, 10 15 seconds to heat up and trip 30 seconds to cool back down and restart) If so you need an amp probe to measure the compressor current draw, compare this to the label on the compressor. If current draw is over that stated, sounds like compressor is faulty. If its been running with no condenser fan for any time my money would be on a faulty compressor.

Jon