Trying to fill A/C system; blows hot air and high side has low pressure

[WHO1DMC]

Oops I didn't catch David Ts accumulator booboo. Ha!


Dave B.

[Ron]

Lmao! ..what ya get for agreeing with him

[Bitsyncmaster]

FYI:

You should not need to jump the low pressure switch to start charging the system. When you open your can of refrigerant the gas pressure is above 50 PSI. Now the can will get cold pressuring the system that should be sitting at a vacuum so you put the can in a pan of hot water and wait till the can has emptied. Keep the can vertical so only gas is used for charging the system engine running, AC on normal, blower on highest speed, doors open.

If it's really hot when charging your compressor may never cycle at idle RPM which is normal. It all depends on the air flowing over the condenser and evaporator and engine RPM.

You test your low pressure switch operation by reducing the blower speed which will let the system pull the low pressure down to let it cycle. When your driving the higher RPM and more air flow over the condenser normally make the compressor cycle.

[jangell]

Thanks everyone. This weekend I have to replace the water pump, so while I have the belt off I can confirm which ports are which on the compressor by turning it by hand.

So what I'll be doing is:
- Verifying the compressor high/low ports by turning it manually and seeing which port sucks and which port blows, just to be sure.
- Verify compressor mounting
- Verify compressor oil
- Replace the orifice tube and accumulator? Should I bother with neither, one or both?
- Vacuum the system for an hour to make sure it's evacuated
- Turn on the key and jump the low pressure switch just to make sure the compressor works, then plug it back in as normal.
- Put a box fan in front of the radiator
- Turn on the engine
- Fill with 30 oz from the low side with the engine and compressor running. The compressor should start automatically soon after the first can starts being drawn into the system. If not, jump it until the first can is empty?
- Use the warm water trick to get more refrigerant out of the cans.
- Once filled, adjust the low pressure switch for R134a.
- Test the low pressure switch by reducing the blower speed and see if the compressor cycles.

Thanks!

-- Joe

[Ron]

DeadHorse.jpg

[jangell]

Ah, right — I’ll add that to the list. Thanks!

— Joe

[Rich]

A reference here to a Sanden manual to consider as you look to tear back into it:

You mention the unit is a Sanden SD709. The manual for that model is HERE

Among other things there you will see which port is the D (Discharge/high) side and which is the S (Suction/low) side.

Looks like the D and S letters are embossed on the compressor cylinder head assuming the sketch on p.8 applies to this model. If so then these ports are reversed vs the Sanden model that DeLoreans came with. You might get a mirror or camera back there to verify which port is stamped as which on your unit. The rotation test you plan may verify.

The SD709 is listed as a R-12 model, not a R-134a model, in Secs. 1.0 and 2.0 of the manual. Whether that's important or not I don't know.

[jangell]

Great -- thanks, I'll check for those stamps this weekend too.

The Four Seasons 58555 (which cross-refs to the Sanden SD709) is both R12 and R134 compatible, at least according to their spec sheet, so I'm good there.

Thanks!

[David T]

While the compressor may be able to run -12 and -134, if it contains the wrong type oil you will have problems. The safest thing to do is just remove the oil and fill with the proper one for the type refrigerant you choose. Because you can still get -12 you should use it and not -134.

[jangell]

Sounds good. If I remember correctly it came filled with the correct oil for R134, but it won't hurt to drain and refill it.

Spec page, confirming R134a oil and seals: https://www.4s.com/en/ecatalog?part=...ype=p&search=s

-- Joe