AC System From Scratch - 1989 325i

[gilber33]

So the E30 I picked up a while ago has the ac system entirely removed froward of the firewall. RealOEM helps me get an idea of what lines/hoses IÂ’ll need and some pictures I have found give me an idea of the dryer install and location. But it now I am having a hard time understanding the evaporator temp sensor thatÂ’s on the dryer. I think I found the compressor connector: The aux fan switch on the radiator connector: That just leaves this one: Is this for the evap temp sensor on top of the dryer? And if so, how do I know which temp sensor my car is supposed to have? I think I saw there are a couple different styles.

[roguetoaster]

The three wire is for a temp sensor in the rad, where that brass plug is, and the three prong with the looped connection might be for the old style pressure switch with 134A conversion, or for the compressor depending on the compressor spec'd for the car from new. Either way, the compressors available today will probably be one wire, and are often a flat single connector.

[gilber33]

The three wire is for a temp sensor in the rad, where that brass plug is, and the three prong with the looped connection might be for the old style pressure switch with 134A conversion, or for the compressor depending on the compressor spec'd for the car from new. Either way, the compressors available today will probably be one wire, and are often a flat single connector.

I looked up used compressors for this car and they had the connector that the one with the looped wire would fit in to. I need to figure out what that third connector is for though. That one I assume is for the evap temp sensor on the dryer but I’m not sure and couldn’t find an example of one that this would plug into. Sent from my iPhone using Tapatalk

[gilber33]

I found this picture on ebay of a dryer and it looks like the round connector with the two female ends would fit this. Is that the pressure switch? And then the other sensor is the evap temp sensor? I did not find another connector in there that would fit that other sensor. Maybe it got tucked under the fender or something.





So the more reading I do I see there used to be a high and low pressure switch that was updated to a single pressure switch. To have the updated system, do I need something like this which would involve eliminating the round, two-prong connector and replacing it with the female connector included in the kit pictured below:



And also found this thread which shows what I assume the dryer in my e30 looked like and the newer style one that went from the two switches to one. A couple posts later it says you take either connector from the original setup and splice in the connector for the new pressure switch and the remaining connector gets a jumper wire. My only problem is I didn't see the other pressure switch connector - just the one. Hopefully it's tucked down into the fender or something.

[SethB]

The first image (3 pin connector with two pins jumped) is the compressor clutch, usually one wire running from behind the clutch on the compressor, and obviously plugs into the pin that's not jumped.

2nd pic is the radiator temp sensor as RogueToaster mentioned.

The 3rd connector is the high or low pressure switch (I forget which) that goes onto the dryer. There is no temp sensor on the dryer. Originally there were two pressure switches, one for high pressure, and one for low pressure. The newer dryers for converting to R134a have a combined high/low switch. So either there's another connector floating around in that area (look up front underneath the headlights), or it's already been jumped. Check out the Google Docs link at the bottom of the first page here to get the official BMW tech bulletin for the conversion:

https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/313178-converting-to-r134a-read-this-before-doing-it?t=342398

Good luck!

[mach schnell]

Is this a crazy difficult job....?

[roguetoaster]

The hardest part of the job will probably be vacuuming/filling the system, every component should be fairly accessible.

[gilber33]

The first image (3 pin connector with two pins jumped) is the compressor clutch, usually one wire running from behind the clutch on the compressor, and obviously plugs into the pin that's not jumped.

2nd pic is the radiator temp sensor as RogueToaster mentioned.

The 3rd connector is the high or low pressure switch (I forget which) that goes onto the dryer. There is no temp sensor on the dryer. Originally there were two pressure switches, one for high pressure, and one for low pressure. The newer dryers for converting to R134a have a combined high/low switch. So either there's another connector floating around in that area (look up front underneath the headlights), or it's already been jumped. Check out the Google Docs link at the bottom of the first page here to get the official BMW tech bulletin for the conversion:

https://www.r3vlimited.com/board/for...ng-it?t=342398

Good luck!

thank you! I found the other plug tucked into the wire harness.

[gilber33]

The hardest part of the job will probably be vacuuming/filling the system, every component should be fairly accessible.

I’ve had ac systems completely apart and reinstalled and always take it to a shop and they’ve refilled it no problem. They didn’t need access to anything other than the Schroeder valves.

[mach schnell]

Do you have to remove the dash to install all the lines?

[tomstin]

Do you have to remove the dash to install all the lines?

No, but the center console, lower trim around the HVAC box and glove box will need to come out. And the "fun" part will be getting those hoses through the bulkhead grommet. Patience, patience, patience...

There is a sensor on the driver's side of the evaporator that shuts down the AC if the evaporator freezes. You may want to jumper that or add that to your replacement parts list as that little bugger can drive you crazy if it goes bad.

Another thought, you may want to pick up a copy of Rob Siegel's "Just needs a Recharge The hack mechanic guide to vintage air conditioning". A worthwhile investment if you're new to AC service.

[gilber33]

Everything behind the dash is still there, my first post is about everything in front of the firewall under the hood. I'm not new to AC service, I've removed them, reassembled them, replaced them, etc. in older Volvo's. This is my first e30 so before I went about reassembling this one, I wanted to make sure that the correct connectors were still in the car and not removed.

[jeffnhiscars]

There is no need to remove the console to change out lines, X valve or evaporator...basically anything inside the car other than the HVAC box itself.

Keep in mind that the evap probe is very soft so if you replace the evaporator, which does not have a passage for the probe, do not use the probe itself to pierce the fins. I did that and it deflected and blocked the blend door so I had only moderate heat or an entire winter. Use a thin phillips screwdriver to pierce the fins in a straight line before you install it.

oh...the green switch with the plastic connector is LP and the HP switch has 2 individual male prongs. I actually had a slow leak at the LP switch that had me baffled for years

[gilber33]

Keep in mind that the evap probe is very soft so if you replace the evaporator, which does not have a passage for the probe, do not use the probe itself to pierce the fins. I did that and it deflected and blocked the blend door so I had only moderate heat or an entire winter. Use a thin phillips screwdriver to pierce the fins in a straight line before you install it.

Thank you for the pointer! I would have not even known about that.

[mach schnell]

No, but the center console, lower trim around the HVAC box and glove box will need to come out. And the "fun" part will be getting those hoses through the bulkhead grommet. Patience, patience, patience...

There is a sensor on the driver's side of the evaporator that shuts down the AC if the evaporator freezes. You may want to jumper that or add that to your replacement parts list as that little bugger can drive you crazy if it goes bad.

Another thought, you may want to pick up a copy of Rob Siegel's "Just needs a Recharge The hack mechanic guide to vintage air conditioning". A worthwhile investment if you're new to AC service.

Awesome, thanks. Now to find all the AC parts.......!!