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Old 05-30-2014, 02:46 PM   #21
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Originally Posted by Coop View Post
Just make sure your window regulators dont go out. That happened to me after I deleted mine. South Texas summers with no a/c and a broken driver side window reg suuuuuuucks.
I just put in brand new regulators on the driver and passenger side. With new crank handles as well. I lubed them up like crazy and they slide like butter for now. I plan to lube them up ever summer.

But I have decided to keep the A/C system now. A new console unit for just a radio instead of the A/C controls was going to cost like $300. So that was motivation enough to keep it, and try to get it working again.

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Originally Posted by 2ndGearRubber View Post
Alright my friend, first things is first. YES, damage MAY have occurred to the system as a result of atmospheric contamination. The main component to worry about is the orifice tube, which allows the compressed refrigerant to be released under pressure, change phase, and absorb energy at the same time. However, the odds that it saw significant damage are low.

Second, R12 is not required. 134A runs just fine in R12 systems, with a few adjustments. First, you'll need a set of R12 to R134A adapters for the machine.

Amazon.com: ATD Tools 3525 R-134a Coupler Conversion Set: Home Improvement

These should not be left on the car after the service is performed. You'll also need the spec refrigerant weight for the system, using the R12. Subtract about 20% of that weight, and that's the "correct-ish" amount of 134A to use.



When replacing the compressor, you'll need to replace the receiver/dryer, and if the orifice tube is easily assessable, do it too. Most shops will have an o-ring assortment, but if you can find a set, buy it just in case. Remember to oil the compressor before installation, with the correct spec oil, and turn it by hand to flow the oil throughout the pump. Get a mixing cup with fluid ounces increments, and feed it into the low-side port. Most pumps recommend 10 complete turns. I do 25. Lots of pros kill brand new compressors, because they tried to skip that 5 minute step. They typically only make that mistake once.


When driving to the shop, the system will obviously have atmospheric air present. Do not run the compressor. Until it has been properly serviced and vacuumed, damage may occur. You'll do 3 main vacuums. First down to 20hg or so. It will likely chug and work for minute or two to hit that. Let it sit for 5 minutes or so. Then, hit it for for 30minutes, continuously. Afterwards, you should be in the 26-28hg area (gauges often read a tad high). Let it sit for 15/20 minutes. If pressure drops more than 1hg, you have a leak. No-biggie though, the system must have a 134a charge to function and circulate the dye anyway. After sitting, run vacuum for another 5/10 minutes, then charge. Always make sure to inject your dye (1/4 inch on most dye-gun scales is plenty). Brake clean will remove any spilled dye around the low side injection site. I recommend doing this will the car is running, as it takes the dye much easier.


Then fire the bitch up, and enjoy the AC.



Check in a week or two with a UV light for leaks. No need to break out the manifold gauges. As for AC-in-a-can, and "stop-leak". You'll ruin the system, period. Refrigerant and oil are ALL that should be in the system. Dye isn't really supposed to be in the either, but it doesn't have the hydro-carbons and adhesives the AC-in-a-can **** does.





And **** those fancy Robinair machines. Find an older guy, likely at an indy shop, with an older machine. I love my machine, and it's at least a decade old. Mechanical valves and standard switches.
Thanks for this information, wish you were down here in AZ to help me out!

Last edited by FRT_Fun; 05-30-2014 at 07:02 PM.
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Old 05-30-2014, 06:35 PM   #22
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AKAIK, there is no orifice tube.

Our system has an expansion valve, and that's located near the evaporator in the air handler box under the dash. Unless you have reason to suspect its failed somehow, I would leave it be.
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Old 05-30-2014, 06:44 PM   #23
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Our system has an expansion valve.
Just as an FYI in case you missed it, this thread is about a '76 BMW, not a Miata.
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Old 05-30-2014, 07:03 PM   #24
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Quote:
Originally Posted by sharkythesharkdogg View Post
AKAIK, there is no orifice tube.

Our system has an expansion valve, and that's located near the evaporator in the air handler box under the dash. Unless you have reason to suspect its failed somehow, I would leave it be.
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Just as an FYI in case you missed it, this thread is about a '76 BMW, not a Miata.
Definitely key concept here Thanks for the attempted help anyways.
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Old 05-30-2014, 09:23 PM   #25
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Quote:
Originally Posted by Joe Perez View Post
Just as an FYI in case you missed it, this thread is about a '76 BMW, not a Miata.
Meh, orifice tube and expansion valve are often used interchangeably. Most parts stores/sites, will list "orifice tube" regardless of which kind it actually is.


Kinda like miatas having listings for struts.




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Old 05-30-2014, 10:04 PM   #26
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Oh right! Yeah, I lost track of that somewhere. Apologies.
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Old 05-30-2014, 11:22 PM   #27
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Air Conditioning Basics - BMW 2002 FAQ

I'd have a shop pressure test your aftermarket evaporator blower unit, to make sure it's worthy of spending a dime on. You'll also want to flush the crap out of it, and if it has any significant circuitry, check it for failed components, since it's nearing 40 years old. I'd then put in a Sanden compressor in a heartbeat, with the recommended parallel flow condenser and electric fan. While you're doing that, you might as well slap on a 12" electric fan on the radiator and ditch the clutch fan. Get that receiver drier kit, and see if a local hydraulic shop will crimp the hoses for you after you install everything and clock the fittings. Bring donuts or beer and it might even be free!

You'd be looking at $150 for a new sanden style compressor, or find a good used one. $60 - $160 in fans, $50 hose kit, $50-$100 for a condenser. You could do all of it and have a brand new cold a/c system that won't leak with good components for $600 if you install everything yourself. You could probably get down to ~$350 if you skipped the radiator fan and went used compressor.
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Old 06-01-2014, 09:54 AM   #28
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fwiw- I'm running Envirosafe ES12 (hydrocarbon blend) in my 87 Benz using all the original components (originally designed for r12.) I have 43f at the vent with 85f ambient. But IMO that's the easiest solution if you're ok with using a hydrocarbon refrigerant. The ES12 is showing 80psi high side pressure- less than the original R12 and significantly less than R134.
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Old 06-02-2014, 01:42 PM   #29
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I'll see what I have first. I found the manual for my original BEHR kit so I'll be going through that again to figure out what exactly I have going on. I can't really get to the condenser, but it looks to be horizontal tubes, if that means anything. I would imagine it is still r12. I have no real preference to what I use as long as it is cheap and at least makes the air a little cooler.
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