Air conditioning Service Questions

[CblockM3]

Hi Everyone,

I've had a leak in my AC system for a couple years and am planning on doing a service this month. I filled up the system enough to kick the compressor on and ran dye through it. It looks like it is leaking at the dryer and possibly the condenser, so my plan is to replace them both. I've never serviced an AC system so I have a couple questions I haven't found from searching.

My plan is to replace those two components and replace all of the Orings. Hopefully this seals the system and when I pull Vacuum I won't find any leaks and can add in my refrigerant.

First question, is it possible to replace the compressor oil without pulling the compressor? I don't see any leakage around the compressor clutch and it seams to operate fine, I'm hoping not to pull it if I don't have to. I'm also assuming I would need to replace the oil before pulling vacuum?

Second question, do you add any oil to the dryer before pulling vacuum?

Third question, is it worth pulling everything out anyway to flush everything? The system and compressor work great with pressure in it, it kicks on like it should and runs fine and blows cold until it leaks out.

I think I have a pretty decent grasp of what I need to do but if it sounds like I'm way off base here please let me know.

Thanks!

[scooper]

Pull one of the lines going into the compressor and use a syringe to add oil. I think some refrigerant might come with oil in it already (though I did not use that). I don't think you need to add oil into the dryer. Find out where the leaks are and replace those o-rings. You don't need to open everything up.

[marvinstockman]

Youtube is your friend.

[Twistytee]

If you're going to be pulling lines you should have the refrigerant professionally evacuated from the system. I know you're aware of this but it's illegal to release it to the atmosphere by pulling a line or removing components. Oftentimes new compressors come pre-oiled, so check the manufacturer paperwork. If you first drain oil from the failed compressor drain plug, measure it so you can calculate total system oil based on manufacturer ratings. Generally the condesor and drier each take 1 oz and the accumulator and evaporator each take 2 oz. If filling the system from scratch, half of oil capacity can be added to the compressor and half to the drier. The system will then distribute the oil to the other components.

I haven't rebuilt the system on the e36 so the manufacturer specs maybe slightly different. Yes you need to replace the oil before performing the vacuum test. The refrigerant itself can be used to flush but this requires a/c equipment to perform a closed loop power flush.

[CblockM3]

Youtube is your friend.

I've watched a ton and rarely make a new thread for something unless I feel like I really need to to understand something. Thanks though, your old ac thread was of no use to me.

If you're going to be pulling lines you should have the refrigerant professionally evacuated from the system. I know you're aware of this but it's illegal to release it to the atmosphere by pulling a line or removing components. Oftentimes new compressors come pre-oiled, so check the manufacturer paperwork. If you first drain oil from the failed compressor drain plug, measure it so you can calculate total system oil based on manufacturer ratings. Generally the condesor and drier each take 1 oz and the accumulator and evaporator each take 2 oz. If filling the system from scratch, half of oil capacity can be added to the compressor and half to the drier. The system will then distribute the oil to the other components.

I haven't rebuilt the system on the e36 so the manufacturer specs maybe slightly different. Yes you need to replace the oil before performing the vacuum test. The refrigerant itself can be used to flush but this requires a/c equipment to perform a closed loop power flush.

Thanks for the response. I think I'll move on with my initial plan and take it to a shop to evac and refill the system. I ran it tonight for about an hour, the first 30 min the compressor would engage/disengage about every minute or so it seemed, going from about 25 psi with the compressor engaged and up to about 35 psi when disengaged. The last 30 min the compressor was engaged almost the entire time which leads me to believe the system was losing pressure the longer it ran. I see dye on the lines going into the compressor and dye on the high pressure side before going into the condenser. I'm planning on replacing all of the o rings on said lines. Anything else it sounds like I'm missing?

[Twistytee]

Per your plan, I think having a shop do the evac, vacuum test and recharge is a good idea. Their machine can perform the system flush at the same time, or you can buy a $20 can of chemical flush and do it at home while you're replacing components. Always replace the drier when you open the system. Some people don't but the desiccant is shot once outside moisture is introduced into the closed system. It will never cool directly unless replaced. Same is true with adding oil - add before system is closed and vacuum is pulled. You don't want to open it back again to add more oil. This is why many recharge kits come with oil added to the refrigerant in case you need a touch more but don't want to open lines. Your compressor could be ok since the clutch is engaging and disengaging - this is a good sign. I might still replace given all the other work you are doing and the fact the bearing doesn't last forever.

The only other issue you might have but is not a common failure point is the expansion valve. Unfortunately it's under the dash and not an easy diy. Since you've identified leaks using the dye, I don't suspect your have a metering problem so I would leave the valve alone.

Below low is a pretty good write-up from someone going through the same process. Even if you have a shop handle some of the work, he lists details on oil capacity and o rings plus how he chose to flush the system. Use a respirator and goggles if you plan to flush your own system. He also went with a used compressor due to costs, but I've seen some pretty good prices online for Denso units. Good luck!


https://www.bimmerforums.com/forum/s...eplacement-DIY

[CblockM3]

Thanks again! I've read through that thread several times, it is one of the better ones that document the AC system for our cars. I'm on the fence about replacing the compressor, I'd rather save the money if I can but I only want to do this one time too.

[Twistytee]

Based on your description, I think your compressor is working so I probably would not replace. I replaced the o rings, rebuilt the POA valve, added PAG oil and re-installed on my 50 year old Pontiac. It holds a vacuum fine now and the clutch on the rebuilt compressor cycles as designed. The evaporator and lines are all still original. O rings shrink over time and PAG oil can weep at the bearing (old GM units are designed this way intentionally for lubrication) which eventually requires servicing or replacement of the compressor. If you later find out you should have replaced the compressor, it will cost another ~$100 to properly discharge, replace the drier again, add oil and recharge the system. Gamble $100 and re-use the compressor, or pay more upfront for piece of mind on a fully refreshed ac system. Unfortunately it's not a perfect choice but these cars are a bit needy and it's not practical or affordable to replace all parts when tackling these projects.

[CblockM3]

Thought I would follow this thread through even though it is winter and no one probably cares about their AC right now.

I ran dye through the system and could tell both lines at the compressor were leaking.

I replaced every O ring in the system, put in a new dryer, and took it to a shop which put a vacuum on the system, verified no leaks and did a refill. $160 later and the AC in this car blows COLD.

[golgo13]

$160? My A/C is not working and I've had the dryer and leaking line replaced including having the system recharged for $900.

I feel like I got fucked with no lubricant.

I'm still trying to get my system working, so I'm going to start with the filter, then the sensor and finally the relay and see if the damn system will kick on.

The tracks out here in CA get to 100*F+ so A/C for highway driving to and from the track is an absolute must.

Glad you got your stuff sorted though!

[CblockM3]

$900! Ouch, that must be California tax. Good luck getting it sorted, I had my AC cranked all summer and it was very nice.

[golgo13]

Tried a couple nights ago putting 12v direct to the compressor and all it did was click while the car was running.

Just dropped another $190 on a new Denso compressor via Rock Auto...

The plot continues...

[CblockM3]

Good luck! It'll be worth it when you have ice cold ac!

[golgo13]

New compressor
New o-rings
Recharged freon
Still not working
Stay tuned!

lol....

[golgo13]

Just to follow-up, it turned out that when I swapped magnetic clutches I did it incorrectly, which then fried the fuse and relay.

Swapping out the compressor, fuse and relay got the A/C working.

Just in time!

[CblockM3]

Glad you finally got it figured out!

[scooper]

Man I wish I could get my a/c working properly. I replaced the compressor with new denso unit, new drier, and new pressure switch attached to the drier, replaced o-rings, pulled vacuum, and installed correct amount of refrigerant plus some more pag46 oil. No cold air until I jump the compressor with a wire from the battery so I know the system works. Checked the fuses in the fuse box. They are ok. I read about the final stage unit but I can vary blower speed so I think that's not the problem.

Anyone with some ideas before I bring it to a shop? Worst case I string wire through the passenger compartment and install a fused relay switch to turn on the compressor manually. Thanks for any suggestions!

[scooper]

anybody?

[Eric93se]

Could be a relay issue, I'm not sure you should look in the Bentley manual, for some the Comfort Control Relay could be a part of that system. There is also a pressure switch on the reciever dryer called a Trinary switch (safety pressure switch) that detects if there is too much pressure (not 100% sure) the system won't turn on. You should update your profile yr/model.

[MParallel]

Here is the E36 HVAC documentation from BMW. It uncludes how compressor control works. Might be of help

https://e36-talk.com/index.php?attac...-ihka-e36-pdf/

[scooper]

Thanks gents...I'll have a look at that documentation. I replaced the comfort relay yellow thing in the fuse box and replaced the pressure switch at the drier already. No change.
I'm wondering if it is a bad capacitor on the pcb of the climate control unit. All pixels are good, blower speeds work, and the snowflake lights up but no cold air....a head scratcher.

[Eric93se]

Scooper, that PDF shows the DME is responsible for turning on a relay which then energizes the compressor clutch. Be sure to find the correct relay box layout for your year/,model because they are not the same.

[scooper]

Thanks Eric...I haven't finished going through that PDF yet. So far I thought I'm thinking my climate control unit might be bad in some way...but from what you say the DME seems to share some role in turning on the A/C compressor....Hmmmm...

[MParallel]

You can easily swap out the control unit to at least rule that out.

[scooper]

Yeah I'm trying to acquire another control unit to see if that is the problem. I'm looking at the pdf pages 364, 365, 367, 368 of 502, and I am wondering what is the function of the a/c climate control module? located under the sunglass cubby under the carpet rug? I vaguely recall that this black module box is a part of the a/c circuitry system. Thanks for any help!