A/C help
 

Car is '88 560 SEL with R134a downgrade performed by PO

No cold air at all
Looking though sight-glass I see no fluid
Now have 134a canister and hose to connect to system
When I pressurize system the compressor clutch does not engage.
I do not belive entire system is pressurizing

I'm following the instruction on the refridgerant can and no luck... any advice?


Thanks!


Scott

Find the pressure switch at the receiver drier and WITH THE ENGINE OFF remove the connector and short the pins at the connector while ignition is on AND ENGINE OFF. You should here the clutch click. If not, troubleshoot the electrical problem until it does. ALSO WITH THE ENGINE OFF, turn the forward most plate on the compressor by hand to ensure that the compressor rotates freely with no metallic feel, you will only feel smooth compression pulses.

THEN use correct manifold gauges to check your charge. Don't use a suicide hose. On any system you SHOULD check high side pressure, but on a converted system it is IMPERATIVE that you monitor high side pressure.

Good luck,

what if you dont feel pulses?

If shorting the pins engages the clutch, you are very low on refrigerant, out of refrigerant or as stated, dealing with an elect. issue; that could include a faulty pressure switch.

With a set of gauges suited to your refrigerant, you could at least check the static pressure. That would give some indication as to whether or not the system has sufficient juice to get things started.

You have lost the charge, most likely. Major leak points on converted systems are any o-ring not replaced (they deteriorate after conversion, whether from the oil or the R134a I don't know), leaky evaporator (not common in the W126, overly familar to W124 owners), bad hose to compressor seals, and eroded seals between the aluminum hose manifold and the actual pump.

I've had all of these, and am still chasing down the leak on the TE after 5 years, darn it!

Look for oil on the hoses -- oil is a resul of a leak. Most 0-rings are fairly easy to replace, you can get the correct green ones at any parts store these days cheap.

However, if you do not have a good vacuum pump and a reliable set of gauges, you won't be able to fix this correctly and run the risk of wrecking a pump, and that can mean replacing the evaporator and condesor to get rid of the debris.

Follow Larry's advise, he knows what he is doing!

Peter