Hello all:

The compressor on my '92 245 will not engage on its own. I can get it to run by (briefly) jumpering the low-pressure switch on the accumulator. I am not equipped to test for pressure in the system at home, but I did trace all the lines and had a close look at the condenser-- everything looks fine-- no black goo or oil on any of the joints.

I know that this is a classic symptom of low system pressure, but are there other things I can rule out first? How do you test the low pressure switch? Are there any relays that I should examine-- if so, where are they located? Again, this is a '92 with the later 700/900 style AC.

Any/all wisdom would be appreciated!
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Herb Goltz, London, Ontario, Canada '92 245 w/102K mi

I added R134a to all four of my cars. It's not hard to do. If your system uses R134a, then it was converted from R12. R1334a will bleed through the lines over a year's time and will need recharging, if you live in a cold climate. I assume the Florida guys run theirs daily and probably don't have a problem.

Klaus
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95 850, 88 245

Hi Herb:
You really do need to check the pressures. If you jump the switch and it works it might be that the low pressure switch is bad, but it is more likely low on refrigerant. If you are running r12 you probably need to take it to a shop to have the pressures read, unless you have a friend like Greg with all the equipment available (or you want to go out and buy a set of gauges). If it is an r134 car you can pick up a cheap gauge/refill bottle combination at any of the discount stores (such as the Interdynamics Measure & Charge kit; see it at http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=IDN&MfrPartNumber=MAC134&CategoryCode=3571) that you can use to check the low pressure side pressure anyway and see whats up. My bet goes with low refrigerant level.

Hope this is helpful.

Mike
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Mike Brown Greenville, NC 1996 965 105K 1994 940 135K 1986 244 137K

Those swiches do not often fail. Does the system start to cool when you jumper the switch. Just feel the vacume hose. If no then thats a pretty good indication that you are low on freon. If it cools normally then it would be the switch or posssibly a problem elsewhere, possibly elctrical.
I vote that the switch is OK.
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David Hunter

Hi Herb,

Well if the compressor clutch engages when you jumpt the switch, then likely static pressure has dropped below min. I have never heard of the switch going bad. I guess you can make sure the contacts at the connector are clean... but unlikely the issue.

Car is still running R12 or R134?
Too bad you are not near Ottawa, I can check it for you using my guage set to confirm the pressures. I have a mastercool pump and a vacuum leak detector and would gladly have done a vacuum test on it to help you pinpoint a potential leak (since you likely have low refrigerant).

Good luck!

Regards,
Greg Mustang
Montreal-Ottawa
Canada
greg_mustang@hotmail.com