89 lesabre

[Gocart879]

hello, a few weeks ago i posted about my AC issues with my 89 lesabre Limited with no results. i have the standard ac controls and when i turn on my AC it blows out cold and the compressor runs, but only for about 3-5 seconds every time. it repeats this cycle and im not sure why. i was on the P/A forum reading about relays. Does the lesabre have any relays and could mine be on their last leg? please let me know

thankyou

[kok328]

Have you checked the freon level? It could be that the comressor is short cycling due to low pressure/freon levels.

[HotZ28]

Below is a link for your problem:


http://www.automotiveforums.com/vbul...wpost&t=431604

[Gocart879]

what are the chances the pressure switch went bad, can i test it?

[HotZ28]

Do you know what kind of Freon is in your system? Sounds like it may be one of the aftermarket types, if you have a full charge. They cycle more often due to pressure fluctation, high-low.

[Gocart879]

is that bad for the compressor clutch or the compressor? it blows out nice and cold after about 40-50 seconds of the engine running. i was just concerned becuase of the engine rpms increasing but i now understand that the engine rpms slightly increase to manage the load of the compressor running. so if it doesnt do any harm to the compressor im in good shape. let me know, thanks.

[HotZ28]

Older cars (such as using the infamous GM "R4" compressor), have a switch in the low pressure side of the system which opens at about 24 PSIG, cutting off the compressor. The evaporator warms up, and when the pressure reaches around 40 PSIG, the switch closes again, restarting the compressor. This method causes a lot of wear and tear on the compressor clutch.

The best performance from FRIGC / Freezone/ Freeze12 is obtained when the low side cutout switch is changed from 24 PSIG to about 14 or 15 PSIG. This will reduce compressor cycling to about what R12 sees. However, there will still be about a 25% loss in capacity due to reduction in mass flow due to lower suction pressures compared to R12. (less gas is circulated in the system).


The switch could be tested with regulated air pressure and ohm meter with pressures in the range indicated below; however it would take some engineering with fittings and regulators with accurate gauges. The switch would be cheaper to replace than to buy all the parts needed to test it!

[Gocart879]

so, if i jumpered out the pressure switch permanently, would i cause harm? i was just wondering becuase i dont want to destroy the compressor or have it malfunction
thanks. mike

[Gocart879]

just did another test jumping out the pressure switch, this time i ran the vehicle for about 5-6 minutes and again the compressor ran the entire time, is this a little to long for the compressor to run? so that could mean the freon is low also correct?

[HotZ28]

If I were you, I would check the high and low side pressure to see what your system is doing. Your system was designed for R12 and if it still has pure R12, you should be around 28-30 on the low side and 230-280 on the high side depending on ambient temp. If you are higher than 45 on the low side, you need some Freon. I had one the other day that was cycling off-on about every 30 seconds and it was only about ½ lb. low. Another thing to consider is an overcharge. It will give the same cycling effect due to high pressure.

If you are low on Freon and run the cycle switch bypassed for extended periods, (weeks or months), it could harm your compressor. Usually it will not cool at all before that happens. The system depends on the recirculation of Freon to move the oil and lubricate the compressor.

[Gocart879]

ok, so my next step would be to check the pressure, however what do i use and where do i check the pressure at. Believe me, i know nothing about A/c systems, but when a process is described i can indeed do it. thankyou so much for all your responses.

Mike