Upgrading from standard to dual climate control system?

[CBC]

I apologize if this has already been discussed in the forum previously. I searched the topic and did not find any matches.

My 1995 525i has what I would term the standard HVAC system - the control panel has 3 sliders for vent selection, and three knobs, 1 for fan speed, 2 for temp selection - driver side and passenger side.

My question is, can I easily upgrade that system to the dual climate control set up that was (I'm guessing) an option for that year? Can I just replace the control panel on the dash, along with the control unit (brain) that is located under the dash? Or is it way more indepth that this?

The reason I would like to do this (other than the fact I like the dual climate control set up better), is that I am most likely needing to replace the A/C control unit (brain) on my car. I can get either type control unit for about $225, so if purchasing a good used dual climate control panel is the only other part needed, then I might as well upgrade.

Any tips, help, suggestions are appreciated.

Thanks!

[Dan in NZ]

That is what they call the dual climate control... Because you can control two climate zones (supposedly). There is a more advanced version, that controls the flaps for the air diverter with motors, instead of you moving the levers. I think the conclusion people have come up with, is that it would be far too much work to retrofit all the stepper motors etc.

Why do you say you need to replace the a/c control unit? It's common for the heater valves to stick, causing temperature control problems, or the resistor pack to fail meaning you only get high speed fan.

[CBC]

Thanks for the feedback. I'll stay away from the upgrade...seems like too much work and too many chances for a mistake.

I have been working through a ongoing issue with the air temp at the vents decreasing as I increase fan speed. On speed 1 and 2, I get very comfortable cold air, but on speed 3 it becomes somewhat less cool, and then on speed 4 noticably less cool. I have had all the underhood components replaced and the system has been recharged with 134. I replaced the heater valves with new ones and that did seem to help quite a bit. Two things I am noticing as I observe this problem closer - the air volume from the vents stays the same regardless of my vehicle speed (my other non-BMW cars have more air volume at highway speeds, so this just be a difference with BMW's), and secondly, the compresor (new) seems to cycle on and off frequently - on for 5 or 10 seconds, then off for 5 or 10 seconds. A friend with a 91 525i suggested there was too much freon in the system. The shop that did the repair says it the correct amount is in the there. My firend also recommended the control unit replacement, explaining he had similar A/C problems that were corrected by its replacement.

Any ideas? Thanks

[Bill R.]

temperature setting that you set and it automatically adjust the blower speed, dampers etc to maintain the temp setting, the type that you have now and that other mention is the manual air conditioning,with dual temp setting to allow small changes from one side of the car to the other. There's more involved than just changing the faceplate though, and the climate control system is always more trouble than the mechanical system you now have... I'd stick with what you have. Contrary to what your friend say, short cycling of the compressor and lack of cooling at the higher blower speeds typically indicate a low charge rather than too much. I'd check your system pressures but i'd bet that your low on r134a regardless of what the shop says. You need to check low and high pressures to verify. If you read the following in the last few sentences you'll see the explanation for the air speed not changing at highway speeds.

Thanks for the feedback. I'll stay away from the upgrade...seems like too much work and too many chances for a mistake.

I have been working through a ongoing issue with the air temp at the vents decreasing as I increase fan speed. On speed 1 and 2, I get very comfortable cold air, but on speed 3 it becomes somewhat less cool, and then on speed 4 noticably less cool. I have had all the underhood components replaced and the system has been recharged with 134. I replaced the heater valves with new ones and that did seem to help quite a bit. Two things I am noticing as I observe this problem closer - the air volume from the vents stays the same regardless of my vehicle speed (my other non-BMW cars have more air volume at highway speeds, so this just be a difference with BMW's), and secondly, the compresor (new) seems to cycle on and off frequently - on for 5 or 10 seconds, then off for 5 or 10 seconds. A friend with a 91 525i suggested there was too much freon in the system. The shop that did the repair says it the correct amount is in the there. My firend also recommended the control unit replacement, explaining he had similar A/C problems that were corrected by its replacement.

Any ideas? Thanks

[Kalevera]

Thanks for the feedback. I'll stay away from the upgrade...seems like too much work and too many chances for a mistake.

I have been working through a ongoing issue with the air temp at the vents decreasing as I increase fan speed. On speed 1 and 2, I get very comfortable cold air, but on speed 3 it becomes somewhat less cool, and then on speed 4 noticably less cool. I have had all the underhood components replaced and the system has been recharged with 134. I replaced the heater valves with new ones and that did seem to help quite a bit. Two things I am noticing as I observe this problem closer - the air volume from the vents stays the same regardless of my vehicle speed (my other non-BMW cars have more air volume at highway speeds, so this just be a difference with BMW's), and secondly, the compresor (new) seems to cycle on and off frequently - on for 5 or 10 seconds, then off for 5 or 10 seconds. A friend with a 91 525i suggested there was too much freon in the system. The shop that did the repair says it the correct amount is in the there. My firend also recommended the control unit replacement, explaining he had similar A/C problems that were corrected by its replacement.

Any ideas? Thanks

EDIT: ooops, I misread the volume of air statement -- thought it said LESS air and lower temps at higher fan speeds...Probably want to disregard the following...


When was the last time the microfilter was replaced?

They're notoriously neglected. After years of having an old one stuck in there, you will be AMAZED at the airflow difference (and the smell of that air) with a new one.

best, whit

[Jay 535i]

EDIT: ooops, I misread the volume of air statement -- thought it said LESS air and lower temps at higher fan speeds...Probably want to disregard the following...


When was the last time the microfilter was replaced?

They're notoriously neglected. After years of having an old one stuck in there, you will be AMAZED at the airflow difference (and the smell of that air) with a new one.

best, whit

How do you replace that filter, Whit?

[Kalevera]

Jay, there probably isn't one on your car. It was a post 7/90 addition, I believe. Earlier cars with them (M5) have a sticker visible with the glove box opened.

I know a few people have documented the specific procedure (search? bmwe34.net? shogun's site? I dunno exactly where, but it's out there). In short: remove the glove box, the plastic cowling around the hvac box, and the filter lives by firewall.

best, whit

[CBC]

Jay, there probably isn't one on your car. It was a post 7/90 addition, I believe. Earlier cars with them (M5) have a sticker visible with the glove box opened.

I know a few people have documented the specific procedure (search? bmwe34.net? shogun's site? I dunno exactly where, but it's out there). In short: remove the glove box, the plastic cowling around the hvac box, and the filter lives by firewall.

best, whit

I found the directions in this forum. Can't exactly recall where, but searching "microfilter" might pull it up. I'll look tonight and see if I can find the procedure again.

[Jay 535i]

Thanks all. No sticker in my glovebox, as far as I can see.

[Bill R.]

site is no longer running Here it is
Its a moot point though because i'm pretty sure he doesn't have it, even though a number of them did not have the sticker in the glovebox.

I found the directions in this forum. Can't exactly recall where, but searching "microfilter" might pull it up. I'll look tonight and see if I can find the procedure again.