AC Fix

We finally had a couple decently warm days over Memorial Day weekend here in Brooklyn, so I decided it was time to look into restoring what little AC this car has to offer (even as a new car they aren't known for cabin coolness - unless you do major upgrades, a la The Mister Ice Project.  I was on the fence as to whether or not I should remove the ac components altogether for weight savings, so I likely won't be making these upgrades - but it's an interesting read if you're into AC function and general geeking out).  As luck would have it, my parents were visiting for the long weekend and they drove their '03 BMW 325xi.  Their road-trip vehicle of choice isn't what I consider lucky in this case, nor is the fact that they discovered their car was suddenly lacking air conditioning while on this trip... what I consider lucky is that I went with my dad to the local Pep-Boys garage while he got the Bimmer's AC charged with a fresh dose of "nonfreon."

As dad was talking through the diagnostics with the Pep-Tech, I noticed they had a canister of 134-a refrigerant (make sure your system has been updated to accept 134-a before purchasing/installing) with a trigger release pressure gauge for DIY charging on a shelf in the front of the store. 

For $35 I had to try it.

Before I could take this step though, I had to install the belt which I bought at Pelican Parts earlier this spring.  So we left the store minus one BMW, and while we waited for the call from Pep-Boys, I popped the lid and had a look.

A pretty easy job all told - the compressor pump is mounted on a slider plate secured to a mounting bracket on the right side of the flat 6.  There are 3 screws around the perimeter of the slider plate, all easily accessible with a 13mm open end wrench.  A fourth nut is threaded onto a fixed post attached to this sliding plate which moves the whole assembly back away from the engine pulley to gain proper belt tension:  

bolts used to position compressor and tension belt.  4 on top plate are used to adjust fore/aft alignment

Loosen the three bolts enough to free the slider, loosen the tensioning nut, and the gap is easily closed enough by hand (and a little leverage) to work the belt on.  To get the last bit of belt over the edge of the compressor pulley, I used the handle end of a crescent wrench I had handy -  think of seating a bike tire on a rim.  

belted

Once on the pulleys, tighten the adjustment nut so the compressor slides away from the engine pulley, and voila - a tight belt, ready for coolness.  I don't know what the exact tension specs or v-stretch ratio (I'm making these terms up) are for this particular belt, or if it matters... I tensioned it so it was snug, and when pinching the belt together between the two pulleys, I was able to gain maybe 1/4" - sorry, trying to think metric here:  3 - 5mm of movement on each side.  Felt tight enough - I'll check it in a week or two for stretch, and re-tighten as necessary.  Check that the pulleys are straight relative to each other, tighten the bracket bolts, and you're done.  Easy Peasy.

good pulley alignment is key to non-shredding belts

Now that the belt is on and the compressor secure, I plugged in a random loose wire that was dangling nearby, and fired it up for a test.  Amazingly enough, when the AC knob is turned on inside the cabin, the compressor clutch engages and the compressor starts... compressing!  Time for the gas!

The kit comes with a bottle of compressed 134-a refrigerant, a trigger assembly with a pressure gauge, and a quick release at the end of a 12" - bah... 25cm hose.  The quick release is connected to the low pressure fitting, which is easily chosen out of the lineup wearing a blue cap - remove the cap, and snap on the hose:  

blue on blue for low pressure fitting

With the engine running and the AC on, check the gauge.  It should read at a minimum of 25psi.  Mine read exactly zero - so yeah... needed a charge.  From this point it's ridiculously simple as you squeeze the trigger, slowly pressurizing the system with brand new cold-making goodness.  The process takes about 10 minutes, and I checked every minute or two to see where we were with regard to pressure (the gauge goes flat while actually releasing refrigerant).  With an empty 18oz can (system purportedly handles 20oz max) and a gauge reading 40psi, I figured I was done.

almost there at 35psi

Preliminary testing proves positive, with significantly cooler air forced out of the tiny and rather useless dash vents.  System draws a lot of power from the engine, so I don't think I'll be driving around much with the AC blasting.  But - for hot & humid and/or rainy days, on open-road drives, I definitely think it will be a welcome feature to have running.  I am very impressed by the system, one that sat dormant for a number of years and performs perfectly well with an hour of work for under $50.