BMW E24 AC upgrade(AS OF 2016)

[n2bimmer]

that old valve is a typical, read CHEAP , valve, the one you are proposing to modify appears to be an 88/89 only valve that is required for those cars. Which car do you have ?

Its for my 81 628.

[dcains]

Makes no sense why your "mechanic" should have installed that one, and worse, why he'd leave it open and let the refrigerant vent out. Maybe an exact replacement for the original doesn't exist, but that one is a far wrong as one could be. Hopefully, you can find something which will work.

[n2bimmer]

Makes no sense why your "mechanic" should have installed that one, and worse, why he'd leave it open and let the refrigerant vent out. Maybe an exact replacement for the original doesn't exist, but that one is a far wrong as one could be. Hopefully, you can find something which will work.

I installed the new hoses and expansion valve, he installed the compressor, fan and charged with r134. He said he doesn't know much about the expansion valve... WTH?. So i need a completely different valve? Or should i just install the old one? Ive been told to just cap that fitting and connect the other coil, like how it was before.
Thanks

[n2bimmer]

Based on this thread that valve belongs inside the evaporator box right? Ive never opened my fan unit so I couldn't confirm

https://www.bimmerforums.com/forum/s...-HVAC-Overhaul

[88m53453]

either get the correct valve or reuse the original. I would find the correct valve

[dcains]

Based on this thread that valve belongs inside the evaporator box right? Ive never opened my fan unit so I couldn't confirm

https://www.bimmerforums.com/forum/s...-HVAC-Overhaul

It does need to be inside the evaporator box, because that coil senses the temperature of the airflow and prevents the system from freezing up, which it would if the was no regulation of the cooling.

[n2bimmer]

It does need to be inside the evaporator box, because that coil senses the temperature of the airflow and prevents the system from freezing up, which it would if the was no regulation of the cooling.

I guess ill have to remove the evap box and check it out. It
Would make no sense to have two expansion valves right? Im wondering why then would my car have the valve installed in the glove box area.

[hakeem43020]

that old valve is a typical, read CHEAP , valve, the one you are proposing to modify appears to be an 88/89 only valve that is required for those cars. Which car do you have ?

88/89 front expansion valves would not bolt up to any other e24. They're a different size and use different size fittings(1 size larger). Also close to impossible to find generic valve to replace it and autohauz and many other places list the incorrect valve for it. Although many places list the p/n for it they still send the incorrect valve assuming the earlier ones will fit(they won't bolt up). Hopefully his car isnt such a hassle to find a correct valve.

It does need to be inside the evaporator box, because that coil senses the temperature of the airflow and prevents the system from freezing up, which it would if the was no regulation of the cooling.

Dean is correct, however to anyone reading this with an 88 and 89 the expansion valve is different. RealOEM and every site that shows the valve shows the incorrect valve in their diagram.
s-l1600.jpg
Later e24 valves look something like this with something on the end that sticks out of the evaporator box and is covered with insulation. I forgot this until dean pointed it out. I also didn't insulate mine not sure if that has anything to do with my inside temps.
IMG_4430.jpg
Cant imagine why the front looks like this and the pipe ice cold but blows 60 degree vent temps.

Might be What you mentioned above that's the issue.

I guess ill have to remove the evap box and check it out.
Would make no sense to have two expansion valves right? Im wondering why then would my car have the valve installed in the glove box area.

Not sure how your car is set up since you have an e12 based euro but I imagine 82-87 e24s using one exp. valve in the evaporator housing and the later ones using 2. If you're replacing the valve type in your part number when ordering to prevent getting 100 wrong valves like i did.

This should help.

Also to anyone reading this there a few other things I forgot to mention

Anyone who is thinking to do this on a later e24, think of the later e24s as a complete different car from the earlier ones. The rear ac on later e24s use pipes and mufflers under the passenger that I imagine have a filter inside that are said to not be able to be flushed with solvent. I just ran compressed air though it and let it dry for a few days then blew it out again. Blowing air wont remove all the oil but should do majority of it.

I discovered the back exp valve was replaced twice and even though it's only 2 years old and I rarely used my ac it was still covered with black sludge. The rear pipes were stained black on the insides. The pipes and filters in the rear are said to be used to remove noise or something like that but it does contain small traces of old mineral oil which prevents later e24s from being converted properly because no one flushes/replaces the pipes/mufflers and just throw random PAG oil in the system when converting to r134.

I got a large increase in airflow of the rear after I blew it out my rear and flushed the pipes(NOT THE MUFFLERS).

So if you have a later e24 depending on who converted your system you might possibly have sludge circulating in your rear. My front exp. valve was also original/never pulled, but wasn't as dirty as the rear. I'm guessing this is because of the rear filters/mufflers. So to avoid the sludge USE ESTER OIL or double-end capped PAG. Sanden 508 compressors are shipped with PAG-100 so drain and add ester oil. I didn't do this but I also had my system apart for a few months and ran air through it literally around 20 times. Save yourself time and use ester oil.

I ran air through my rear, used it to test for a week or so and after pulling it apart the sludge reappeared on the valve.

Which leads to another point.
When flushing FLUSH UNTIL THE SOLVENT COMING OUT IS CLEAR. IF ITS YELLOW OR BROWN YOU NEED ANOTHER CAN TO RUN UNTIL CLEAR.
On all e24s before 88 the middle slider(fresh air slider) must be to the left when running the ac to prevent outside air from mixing when running the AC. The fresh air flap is controlled electronically on later e24s and closes when the AC button is pressed.
These may be obvious mistakes but I overlooked these when starting.

[n2bimmer]

Per Realoem https://www.realoem.com/bmw/enUS/par...W-628CSi&mg=64 i dont see a additional valve inside the glove box, only one attached to the evaporator. I honestly dont want to remove the evap box. What if i remove the expansion valve at the glove box and install a threaded elbow? This is assuming the existing expansion valve is still good and wont freeze up? Thoughts?

Thanks

[hakeem43020]

Per Realoem https://www.realoem.com/bmw/enUS/par...W-628CSi&mg=64 i dont see a additional valve inside the glove box, only one attached to the evaporator. I honestly dont want to remove the evap box. What if i remove the expansion valve at the glove box and install a threaded elbow? This is assuming the existing expansion valve is still good and wont freeze up? Thoughts?

Thanks

What refrigerant will you be using? What refrigerant was in your car before? If you're switching then you'll have to replace/take it out to clean it.

[dcains]

Later e24 valves look something like this with something on the end that sticks out of the evaporator box and is covered with insulation. I forgot this until dean pointed it out. I also didn't insulate mine not sure if that has anything to do with my inside temps.
IMG_4430.jpg

That's the "voltage regulator" we were talking about several posts up the page. I still have no idea how it works or what it does, but I'm guessing it regulates the refrigerant flow between the front and rear evaporators.

As for your vent temps, another guess. Maybe the flappers that regulate airflow through the evaporator and vents aren't operating properly? So, either the air isn't passing through the evaporator, or it does, but it's being mixed with warm outside air. The E24 system relies on recirculating the interior air, unlike many other cars which allow you to choose fresh or recirculated air.

- - - Updated - - -

Per Realoem https://www.realoem.com/bmw/enUS/par...W-628CSi&mg=64 i dont see a additional valve inside the glove box, only one attached to the evaporator. I honestly dont want to remove the evap box. What if i remove the expansion valve at the glove box and install a threaded elbow? This is assuming the existing expansion valve is still good and wont freeze up? Thoughts?

Thanks

I'm having hard time picturing what your E12 system looks like, but the expansion valve itself doesn't need to be inside the evap box. To clarify, it's the bulb or coil, which senses the temp of the evap, and that part needs to be inside the box.

[n2bimmer]

What refrigerant will you be using? What refrigerant was in your car before? If you're switching then you'll have to replace/take it out to clean it.

It was and will be 134.

- - - Updated - - -

That's the "voltage regulator" we were talking about several posts up the page. I still have no idea how it works or what it does, but I'm guessing it regulates the refrigerant flow between the front and rear evaporators.

As for your vent temps, another guess. Maybe the flappers that regulate airflow through the evaporator and vents aren't operating properly? So, either the air isn't passing through the evaporator, or it does, but it's being mixed with warm outside air. The E24 system relies on recirculating the interior air, unlike many other cars which allow you to choose fresh or recirculated air.

- - - Updated - - -



I'm having hard time picturing what your E12 system looks like, but the expansion valve itself doesn't need to be inside the evap box. To clarify, it's the bulb or coil, which senses the temp of the evap, and that part needs to be inside the box.

OH I see... Here is what the E12 A/C system looks like. https://www.bimmerforums.com/forum/s...-HVAC-Overhaul.

[dcains]

I think you need to open the box up and see what's been done. That new expansion valve you have might be the correct part, as it appears similar to the on in the a/c overhaul thread - but it's clearly not installed properly. The temp sensing bulb (or coil) needs to be mounted as in the pics (looks like it's held to one side of the evap with some sticky stuff), and that other small pipe looks like it attaches to the side of one of the large refrigerant lines. Maybe your system doesn't require that small pipe connection, but in any case, the bulb (or coil) needs to be on one of the evap coils so it can sense the temp accurately.

[n2bimmer]

I think you need to open the box up and see what's been done. That new expansion valve you have might be the correct part, as it appears similar to the on in the a/c overhaul thread - but it's clearly not installed properly. The temp sensing bulb (or coil) needs to be mounted as in the pics (looks like it's held to one side of the evap with some sticky stuff), and that other small pipe looks like it attaches to the side of one of the large refrigerant lines. Maybe your system doesn't require that small pipe connection, but in any case, the bulb (or coil) needs to be on one of the evap coils so it can sense the temp accurately.

I was really avoiding this process.. im going to try one thing before pulling the trigger and removing the evap box. If it doesnt work i will remove the box. Thanks again.

[hakeem43020]

That's the "voltage regulator" we were talking about several posts up the page. I still have no idea how it works or what it does, but I'm guessing it regulates the refrigerant flow between the front and rear evaporators.

As for your vent temps, another guess. Maybe the flappers that regulate airflow through the evaporator and vents aren't operating properly? So, either the air isn't passing through the evaporator, or it does, but it's being mixed with warm outside air. The E24 system relies on recirculating the interior air, unlike many other cars which allow you to choose fresh or recirculated air.

- - - Updated - - -



I'm having hard time picturing what your E12 system looks like, but the expansion valve itself doesn't need to be inside the evap box. To clarify, it's the bulb or coil, which senses the temp of the evap, and that part needs to be inside the box.

I went home tested the flapper door does work. Connected hoses and refrigerant comes from the high side and air from the low side. Refrigerant should come out the low side too right? Not sure how air would've gotten in there because I purged the line before putting in refrigerant.

[hakeem43020]

Gave this a break and now I'm back. Everything in the system seems good. Went outside to check the pressure reading with my gauge and after disconnecting my red hose from the high side and releasing the pressure I realized that there was refrigerant coming out the yellow hose. gas/air comes also out whenever I press the low side charging valve but refrigerant comes out of the high side. Not sure if this is normal but I'm examining everything closely at this point. The only thing I could possibly think of is a bad gauge set, which is unlikely because it's new. I'm sure I'll figure it out eventually, bet it's something really stupid that I overlooked.

[hakeem43020]

Charged yesterday. I'm getting 45 vent temps from the front and back. It was 65 today so the vent temps will probably rise and ambient temp does. I compared my pressures to the values on the r152 pressure chart after checking it this morning and it seems pretty close. Pressure on both sides were close to equalized, I got close to 57 side pressures on both sides.

I'm guessing because later e24s use a lot more pipes and is a larger system the refrigerant takes a while to circulate. After adding refrigerant the vent temps and pressures didn't drop until the next day. This made it very hard to charge. I found this out because I ran out of cans and added 1 and Temps did not move. I drove it around for a few minutes and nothing butTemps dropped by the next day when I was driving. I added one can a day and monitor the temps each day and Even after I added the last can yesterday it was still at 60 and Didn't see 45 degree temps until today. I approximate that the later e24s will take around 3.XX cans. It was around 55 degree vent temps after 3 and 45 after I added 4 so I probably overcharged, it should be somewhere in between that because that's what the weight calculation gives.

I'll continue monitoring and tweaking.

[slofut]

Dean iirc that valve regulates front to rear system bias, obviously a pressure (voltage) regulator (as you indicated). Read somewhere on settings etc.. but a few years back.

[hakeem43020]

I wish anyone who is hoping to attempt this the best of luck. I haven't been able to figure it out. I could take it to an AC shop but I'm not sure how that'd work since I'm using r152 and I'm not sure how much they'd charge but I'm guessing they'll probably charge an arm and a leg to diagnose it.

I got the low side pressure down to 25 but it doesn't go any lower than that. Even at 25 on the low side I still have high vent temps and it never gets colder than 50 at idle. The best I ever got was front and back at 50. Not sure what else to try at this point.

The only thing I haven't changed is the condenser since it can't be flushed and I doubt that's it. Is there anyway to know if it's the condenser or my fan not cooling enough? I have a 5 series aux fan so I'm not sure if that has anything to do with it. I even bridged my fan to run on high and the inside temps/pressures still don't get any lower.

And When using the r152 temp chart how would I go about measuring it? Should I get those numbers on the chart after the car sits and the low and high side equalize?

[Mason Jones]

Hakeem, I feel for you with the added complexity of the front/rear system. When you get 25 on the low side what is your high side pressure? And I may have missed this but what r152 chart are you using?

[hakeem43020]

Hakeem, I feel for you with the added complexity of the front/rear system. When you get 25 on the low side what is your high side pressure? And I may have missed this but what r152 chart are you using?

It was 25 low and about 150 high.
Im using this chart.

[Mason Jones]

Huh, maybe I'm reading that chart wrong but the numbers for r134a and r12 don't seem to match what I've seen elsewhere like this one: http://acprocold.com/faq/r-134a-system-pressure-chart.

How many ounces of r152 did you end up adding?

[demetk]

The temp/pressure chart that hakeem linked to allows you to determine at what temperature the refrigerant gas entering the condenser condenses to liquid for a given pressure. For example at a 150 psi high side pressure, R152a condenses to a liquid at 120 degrees F. To determine whether there is just enough liquid refrigerant at the bottom of the condenser to service the evaporator as liquid, you then take a temperature measurement of the discharge line as close to expansion valve as possible. Let say that your temperature measurement was 110 degrees F. Then take the difference between 120 and 110 and you get 10 degrees F. This difference is called the subcooling of the system and it, in addition to the superheat, provides you with diagnostic information as to what the problem may be.

Usually I won't need to do subcooling and superheat on my car, although I always do do it on my house HVAC, because if my pressures are good and my vent temps are good then as a hack mechanic I'm good to go. But if you're not getting the vent temps that you should be getting, then subcooling and superheat calculations can tell you where you should be looking for the problem.

If interested, I could do subcooling and superheat measurements from my e28 and we can compare.

Not sure where I got this but I saved it in my info stash.

Possible Diagnosis using Superheat and Sub-Cooling:

If superheat is high and sub-cooling is low:
Charge must be adjusted. System undercharged.

If superheat is low and sub-cooling is high:
Charge must be adjusted. System overcharged

If superheat is high and sub-cooling is high:
Could have blockage in coil or line set.
Superheat is telling you what is going on in the evaporator.
High Superheat = Starved Evaporator
Low Superheat = Flooded Evaporator

Sub Cooling is telling you what is going on in the condenser.
High Sub Cooling = Flooded Condenser
Low Sub Cooling = Starved Condenser

Good luck hakeem and I do hope you figure out the problem. After watching the problems you are encountering with yours, I'm now hesitant to work on my friend's sixer with dual air. He saw the shinny sanden compressor on my e28 and now wants one.

[hakeem43020]

The temp/pressure chart that hakeem linked to allows you to determine at what temperature the refrigerant gas entering the condenser condenses to liquid for a given pressure. For example at a 150 psi high side pressure, R152a condenses to a liquid at 120 degrees F. To determine whether there is just enough liquid refrigerant at the bottom of the condenser to service the evaporator as liquid, you then take a temperature measurement of the discharge line as close to expansion valve as possible. Let say that your temperature measurement was 110 degrees F. Then take the difference between 120 and 110 and you get 10 degrees F. This difference is called the subcooling of the system and it, in addition to the superheat, provides you with diagnostic information as to what the problem may be.

Usually I won't need to do subcooling and superheat on my car, although I always do do it on my house HVAC, because if my pressures are good and my vent temps are good then as a hack mechanic I'm good to go. But if you're not getting the vent temps that you should be getting, then subcooling and superheat calculations can tell you where you should be looking for the problem.

If interested, I could do subcooling and superheat measurements from my e28 and we can compare.

Not sure where I got this but I saved it in my info stash.



Good luck hakeem and I do hope you figure out the problem. After watching the problems you are encountering with yours, I'm now hesitant to work on my friend's sixer with dual air. He saw the shinny sanden compressor on my e28 and now wants one.

Thanks for clarifying, that was really helpful. I was reading the chart wrong. I always heard subcool and superheat but never got what it meant until now. I can check subcooling and superheat tomorrow evening. What do you use to check pipe temps? An infrared temp gun?

[demetk]

Infrared guns are not usually that accurate so try an electronic meat thermometer with a temp probe that you have tested at various temps around the house and on yourself. Hold it in your hand and if you get close to 98.x then you can have confidence in the measurements you're going to get with it. My wife keeps asking me if I know where the meat thermometer went.