1988 325is AC question

Scott R · Scott R's Garage

I had a guy that owed me money give me a really nice 325is, I'm going to sell it probably as I have no need for more cars. It only had two issues, the first was the ABS light, I fixed that by repairing the ABS realy. The next is the AC...

The system is fine, compressor and etc are in working order. However there is a pressure cutoff switch on the front face of the dryer that's leaking. It's a green plug that threads into the dryer like any other switch.

This switch shows no o-ring at the fitting and the switch I removed that's leaking has no o-ring. It's very clearly leaking right out of the threaded fitting, confirmed with a leak detector and the the fact the dye marker is coming . So then I noticed that pelican sells another switch for the same application that shows an o-ring:

Does anyone know if there should be an o-ring there? reguardless of the switch type? I ordered the first switch I linked yesterday from our host.

Also I would post this in the BMW section but there doesn't appear to be a lot of traffic there.....

turbo6bar · 06-27-2011, 07:25 AM

That switch looks very similar to the one on Mercedes systems of the same vintage. The way to know is look at the drier. After removing the switch, you can clearly see a counterbore in the face of the fitting where the o-ring seats. If there is no counterbore, I don't think you need the o-ring.

asphaltgambler · 06-27-2011, 07:29 AM

+1

Scott R · Scott R's Garage

it looks threaded only, let me see if I can squeeze a camera down there. Maybe it's just a bad switch then if it has no o-ring.

turbo6bar · 06-27-2011, 07:57 AM

For clarification, the counterbore is in the face of the drier.

Jared at Pelican Parts · 06-27-2011, 08:05 AM

You first need to tell us what you plan on using as refrigerant, R12 or R134a. IIRC, there are different driers for each refrigerant. and I believe the pressure switch is the same way.

Scott R · Scott R's Garage

The system has had a shadetree r134 conversion, however I'm willing to bet the dryer is original to the vehicle, or at the very least it's "vintage" with the rest of the car. I'll of course be putting a green o-ring on if that's whats required. In the meantime I better hop over to the catalog and see what you have for dryers.

EDIT: I could also refill it with R12, I keep a lot of both on hand.

A930Rocket · 06-27-2011, 08:23 AM

I read some where that there are sending units. One green and one black. Based on Jareds refrigerant post, that might be the reason.

If it's open, you should replace the receiver dryer.

Mine had a new o-ring with the new receiver dryer.

Scott R · Scott R's Garage

The system was closed, had about 1lb of freon in it, just low enough to not trip the switch. But the sniffed leak (and the visual inspection) puts it right at the cutoff switch. So based on all the advice on this thread I just called in and ordered the dryer as well. Thanks everyone!

Scott R · Scott R's Garage

followup on this, there is no o-ring on the pressure switch as was guessed above. I replaced the switch, and the dryer from out host and vacced the system down, everything held perfectly. I flushed the system, charged it and it's a comfy 45 deg coming out of the center vent.

nocarrier · 07-03-2011, 07:58 PM

There are infact two switches on the drier. One is sealed with tapered threads and the other is sealed with and o-ring.

I just use a little loctite thread sealant and have never had a problem.

Check your drier, you will see both the switches on there.

Scott R · Scott R's Garage

Yes the side towards the driver was my leak, the side towards the headlamp I reused with a new o-ring supplied in the dryer that Pelican sent. There are also o-rings on both of the lines going into the dryer, also supplied by our host with the new dryer.