Only way I know to tell if the pressure switch is working is to measure its continuity while measuring the pressure. It's standard procedure to check it after adding refrigerant. All the ones I've seen are closed (zero ohms) with pressure in the system. If one of the wires falls of its better to shut off the system rather than risk running the compressor without oil flowing through the pipes. It's not something you want to bypass long term. Getting metal fragments out of the system from a blown compressor is a real PITA - not to mention the pain of buying a new compressor.
The switch should close at ~ 30 psi, and then open again at ~ 400PSI. The high pressure open protects against a system freeze up - I've never tested it. It depends on temperature, but you should see something like 200-250psi on the high side and 40-50psi on the low side once the system has been operating for a few minutes - assuming you use R134a. Here is a chart if you want to be more precise: http://www.ackits.com/aacf/ptchart.cfm As you are adding vapor to the low side, you will see a sweet spot where the low pressure climbs and the high pressure remains the same. That usually means I'm close to optimal. -Dave Walton On Wed, Jun 18, 2008 at 10:55 AM, Luther <[EMAIL PROTECTED]> wrote: > Low pressure switch was already bypassed by the po. So I pulled the KLIMA > relay and the instant I hit pins 5 & 7 together, I heard the clutch kick in. > I'm going to resolder the KILMA now. > > How can I tell if the low pressure switch is good? The system has full > charge from Monday morning (I hope it hasn't leaked out by now...) > > Luther > > On Mon, 16 Jun 2008 17:55:31 -0500, Peter Frederick <[EMAIL PROTECTED]> wrote: > >> First, check for voltage at the low pressure switch on the reciever/ >> dryer. This is the one with spade lugs and push-on connectors. If >> you have voltage (12V or more) to ground, the pushbutton unit is not >> switching the compressor on. Jumper them together with the engine >> running and the ACC on -- if the compressor runs, either it's already >> low on charge or the switch is bad. If there is no voltage and it >> doesn't run jumpered, time to check ou the KLIMA relay, it's not >> switching on. >> >> You should also watch the compressor when first starting the ACC up >> -- if the compressor runs a few seconds and kicks out, you are not >> getting a good speed signal from the compressor to the KLIMA relay, >> and it will shut of the compressor until you do a power cycle. This >> can be quite annoying. >> >> Finally, you need to jumper the #5 and #7 (I think, will check >> tonight) sockets in the KLIMA relay socket with a large wire -- this >> directly engages the compressor. If it then runs and cools properly, >> you have a problem with the KLIMA relay. There are a series of >> checks there, but no need to get all exited unless the compressor >> ground signal is good and you don't have engagement. >> >> Also check the fuse -- a bad clutch coil will blow the climate >> control fuse. >> >> Peter >> >> >> > > > > -- > Luther KB5QHU Alma, Ark > '87 300SDL (272,xxx mi) head case > '85 Ford F250 6.9 diesel (x58,xxx mi) > '82 300CD (166 kmi) > '82 300D (74 kmi) getting donor engine-sold > '85 300D (280,176) parts car sans engine > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
