AC issues

jesh4622 · 07-31-2017, 01:54 AM

Hi guys,

I recently picked up my 2nd BMW. (My first was an E36 M3)
It's a 128i M sport with the N51.
The AC started blowing less and less cold pretty much since I started driving it in May. The last few weeks it's gotten to be almost completely ineffective and there's gunk all over my air vents.

I searched here on the forums and found this probably means I have an issue with my evaporator.

I figured I would charge the system and and see if I could spot any leaks. Maybe it would just hold a charge, like a few other lucky members on here.

I rented a manifold gauge set from Autozone that looks just like this.

https://www.harborfreight.com/ac-r13...set-60806.html

I picked up some R134 and set to charging the system.
Well, that's where I ran into issues. The first can I messed up on and had the low pressure side closed and couldn't figure out why it wasn't charging. I gave up and lost the can. When I took the gauge set off, I realized the handle had never been screwed down to depress the schrader valve. Yeah, that's a stupid mistake, for sure. I blame lack of sleep.I bought another can the next day after figuring that out.
Tonight I tried it and the system just won't charge. The can brings the low side up to 75psi and the compressor never sucks it in.

I tried heating the can in water and went up to 140psi but the compressor never kicked in.
I tried different settings on the climate control, but none of those got it to start taking in the R134.
My car only has 44k mi on it and the belt going to the compressor is intact and healthy.
At first I was confused because the compressor was spinning, but then further research learneded me that we have a variable capacity compressor.
It should work as long as the air temp sensor, fuses and belt are in place.
Well, I checked the fuses (6,77,88), the belts are beautiful, and my air temperature reads properly in the dash.

Any tips on further narrowing down my problem?

p.s.
I tried to pick up a vacuum pump when I got the manifold set, but I don't have enough in my bank account.

There was still 20psi on the low side and 5 on the high, so I figured since the system had pressure and hadn't been completely discharged, it was OK to proceed.

fun2drv · 07-31-2017, 05:48 AM

I had the evaporator issue on my 135i. It was very hard for the dealer to find since it is buried behind the dash. Ended up paying a hefty repair bill, but it was fixed right the first time. I don't think that this is a job for a "shade tree" mechanic. You do need that AC to be working in tip top shape in Tucson!

Good luck!

jesh4622 · 08-04-2017, 09:40 PM

Well it turns out my weird readings and behaviors I was getting were due to the fact that the manifold gauge set I rented was broken. I got a new one from another location and the system charged correctly. I put in UV dye and if I don't find any leaks and the pressure drops again, I already found a guy willing to do the evaporator replacement. Thank you for replying, fun2drv.

07-31-2017, 01:54 AM	#1
jesh4622 Registered 0 Rep 4 Posts Drives: 2011 128i 6sp M sport Join Date: Jan 2017 Location: Tucson, AZ iTrader: (0)	AC issues Hi guys, I recently picked up my 2nd BMW. (My first was an E36 M3) It's a 128i M sport with the N51. The AC started blowing less and less cold pretty much since I started driving it in May. The last few weeks it's gotten to be almost completely ineffective and there's gunk all over my air vents. I searched here on the forums and found this probably means I have an issue with my evaporator. I figured I would charge the system and and see if I could spot any leaks. Maybe it would just hold a charge, like a few other lucky members on here. I rented a manifold gauge set from Autozone that looks just like this. https://www.harborfreight.com/ac-r13...set-60806.html I picked up some R134 and set to charging the system. Well, that's where I ran into issues. The first can I messed up on and had the low pressure side closed and couldn't figure out why it wasn't charging. I gave up and lost the can. When I took the gauge set off, I realized the handle had never been screwed down to depress the schrader valve. Yeah, that's a stupid mistake, for sure. I blame lack of sleep.I bought another can the next day after figuring that out. Tonight I tried it and the system just won't charge. The can brings the low side up to 75psi and the compressor never sucks it in. I tried heating the can in water and went up to 140psi but the compressor never kicked in. I tried different settings on the climate control, but none of those got it to start taking in the R134. My car only has 44k mi on it and the belt going to the compressor is intact and healthy. At first I was confused because the compressor was spinning, but then further research learneded me that we have a variable capacity compressor. It should work as long as the air temp sensor, fuses and belt are in place. Well, I checked the fuses (6,77,88), the belts are beautiful, and my air temperature reads properly in the dash. Any tips on further narrowing down my problem? p.s. I tried to pick up a vacuum pump when I got the manifold set, but I don't have enough in my bank account. There was still 20psi on the low side and 5 on the high, so I figured since the system had pressure and hadn't been completely discharged, it was OK to proceed.
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07-31-2017, 05:48 AM	#2
fun2drv Lieutenant 262 Rep 561 Posts Drives: '23 M5 Comp Join Date: Mar 2008 Location: Columbia, TN iTrader: (0) Garage List 2023 BMW M5 [10.00] 2023 BMW M5 [0.00]	I had the evaporator issue on my 135i. It was very hard for the dealer to find since it is buried behind the dash. Ended up paying a hefty repair bill, but it was fixed right the first time. I don't think that this is a job for a "shade tree" mechanic. You do need that AC to be working in tip top shape in Tucson! Good luck!
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08-04-2017, 09:40 PM	#3
jesh4622 Registered 0 Rep 4 Posts Drives: 2011 128i 6sp M sport Join Date: Jan 2017 Location: Tucson, AZ iTrader: (0)	Well it turns out my weird readings and behaviors I was getting were due to the fact that the manifold gauge set I rented was broken. I got a new one from another location and the system charged correctly. I put in UV dye and if I don't find any leaks and the pressure drops again, I already found a guy willing to do the evaporator replacement. Thank you for replying, fun2drv.
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