I may relocate my left rear A/C condensor

Hugh R · 06-23-2005, 07:09 AM

My ROW apparently didn't have A/C before it came to the US. and it had a 1/2 assed one when I got it. I've got the seiko compressor, rear deck lid condensor, a fan-powered condensor in the left rear fender well behind the wheel a small condensor underbelly and the front condensor, with a small non-original fan in the front trunk. Running R134a I've got 35 psi low and about 190 psi high, and sitting in the driveway it won't cool below about 60 when its 85 outside.

My friend TonyG from the board has the old York compressor, and only the front condensor with the proper squirrel cage fan and he's also running R134a. He's getting low 40 degree temps with his car sitting next to mine. WTF? I've got almost three times the condensors that he has and his cools better and faster?

I took some temperature readings with a dial thermometer and found that the fan for the condensor behind the left rear wheel is seeing about 120 degree air since its so close to the catalytic converter! I think that condensor is adding heat to the A/C system, not taking it away, so I'm going to remove that condensor and/or relocate it to the front of the left wheel where the washer bottle is located.

'78 SC · '78 SC's Garage

Hugh,

Before you break into any lines to remove the rear fender condenser, you might try blocking off the air flow to it. That would let you test if any heat is being picked up in the condenser (and if it is providing any cooling at all).

BTW, I checked the 134a chart on Dupont's site and at 35 PSIG (50 PSIA) the coolant (not the cabin air) should be around 40 F at the evaporator outlet. If you aren't seeing temperatures in that range, you may have air in the system. Do you know the system holds vacuum? Was it completely evacuated before charging? I'm not an a/c tech, just a rusty chemical engineer.

scottb · 06-23-2005, 09:23 AM

Hugh: I've often voiced my concerns about the left rear condenser. It seems to me that there's just a lot of heat there, and that though the condenser may offer some improvement, having it in the hot environment just doesn't seem to be the most effective way to have airflow over the condenser. I know Charlie Griffiths disagrees, and he markets a complete package for the rear left fender. He's the expert, not me, and I'm sure he's done lots of research, but logic seems to dictate that there are other locations that are better. You mentioned the front left fender...that's where I put an auxiliary condenser and fan assembly (as you know). Griffiths also has a condenser that fits in front of the left rear wheel. That makes a lot of sense to me for a couple of reasons. First, there's less heat there. Second, road debris kicking off the tire would tend to shoot back, behind the wheel. Thus, having the condenser in front of the wheel seems to be a good idea to prevent road debris damage.

Ah, summer is here, and the quest for cold 911 a/c continues. You can almost mark a calendar to predict when the a/c threads will start showing up. Summer is definitely upon us!

RickM · RickM's Garage

Hugh,
Perhaps you can replace the rear condenser with a parallel flow unit. If it works out the sale of your two existing pieces will show you a profit.

Hugh R · 06-23-2005, 10:18 AM

78SC

I've got enough hoses on that condensor in the left rear that I think I can drag it out of the way and see what kind of temps I get. I did pull a vacuum, and it held, its possible that I have an air bubble, but who knows. I know people talk about pulling a vacuum for hours, I did for about 20 minutes and the vacuum gauge wasn't moving.

I'm going over to ScottB's this Saturday to compare his car's plumbing to mine and look at his front left wheel well condensor set up.

'78 SC · '78 SC's Garage

Quote:

Originally posted by Hugh R
WTF? I've got almost three times the condensors that he has and his cools better and faster?

Like you said, it should cool better with all that condenser area. Once you ensure the rear condenser is not picking up heat, you may need to go back to the basics: amount of freon charged, noncondensables (air) in the system, temperatures in and out of the evaporator. Spray the condenser with water, that will greatly improve its performance. If the vents are still not cold, then you have issues other than condenser surface.

I agree with scottb about the rear fender location. Maybe there's enough outside air flowing when at speed so it can function, but it can't be a good place to pick up air when in traffic. Not really the place we want to hang more weight, either. The only real plus is the space is there.