Yesterday morning it [AC system] still had a full vacuum on it. Looking _very_ good! Unfortunately the pressure switch doesn't seem to work, nor did the spare on the parts car.
Went to the U-Pull and got the 190E's auxiliary fan and its pressure switch. Also picked up a headlight assembly, for merging with the one that's missing a mounting ear. (Cut and glue?) Got the headlight mount, too, the plastic one below the light, as one of mine is broken. I powered up the fan on a battery charger and it worked fine. However, the fan didn't install too easily because of the damage from that past wreck. It did eventually go in, and it doesn't even interfere with the condensor which is a bit of a surprise considering the condensor's bent-ness. One complication was getting the fan standoffs (which were also missing) in place: I dropped a sheet metal screw down between condensor and radiator where it lodged point-in. Each attempt to pry the two delicate items apart to look for or to try to retrieve it wedged it in tighter. It didn't seem to penetrate, however, and I was eventually able to fish it out with a magnet. I had to pull the headlight to route the wire, and it seems to me I should have gotten the headlight mount plastic top bits as well. Sigh. The pressure switch installed easily, and works properly. That, at least, is a relief. Using compressed air I got the other two switches responding, but I wouldn't use them except in an emergency. (Or at all if it cost more than $7 to charge the AC system.) Today... The AC held pressure overnight, so I started it up. What a drag, the auxiliary fan runs all the time and the compressor not at all. Time to dive in! The drier's switches for compressor and fan both seem OK. Off to the manuals, I guess. There are relays involved in both functions, it's not as simple as the circuitry in earlier cars. Using the ETM I tracked down the fan temperature sensor and unplugged it. The fan stopped. Great, a bad sensor. I took a small hammer and tapped on the sensor body with it reconnected and the fan shut off. I've seen this before, sometimes it's enough just to do that, the sensor is merely stuck and will behave itself in future. We'll see. I used a jumper to short out both the engine temperature sensor and the drier overtemperature switch. The former runs the auxiliary fan at high speed, the latter, low. Good. The fan system seems to be OK now, modulo that sticky sensor. Nah, that sensor's no good. Its other contact turns off the AC compressor, and it's stuck too. Unplugging it resulted in the compressor running normally. Banging on the sensor did nothing to relieve this problem. I have a spare sensor that I'd bought for my wife's 560 SL last year, which developed a stuck fan contact, but that problem cleared itself up before I could install the new sensor. It's been sitting on a shelf since, I'll probably put it in this car. The full-throttle switch atop the intake manifold also works to shut off the AC compressor, as it should. While doing this testing I noticed a large fuel leak out of the injector return line between #'s 2-3. That's new. I pulled it off and replaced it with new line. I started putting in a test charge of refrigerant. It fills slowly, perhaps because it's not too warm out yet today, or perhaps because there is a restriction in the low-side valving. (I've seen that before.) But I was able to get a fair amount of test refrigerant in there and I was starting to get reasonable pressures. Unfortunately my vent temperatures never got very low, and I thought I even detected some heat coming out the center vent. The sight glass showed plenty of refrigerant flow. (Very foamy, as is normal for this refrigerant.) So I pulled the access panels to the water valve and had a look. It's not always shut off properly. I don't know if it's a control problem or a vacuum leak problem, this will bear some looking into. I manually pulled the valve shut, and then I could feel the vacuum system kick in, but that never really changed anything at the vents. The water pipe remained pretty hot. I wonder if the water valve leaks? (I know it can take awhile to pull the heat out of the heater core at summer temperatures.) Gotta dive into that too. Only one of the horns works. Shoulda grabbed that horn bar at the U-Pull! Maybe I'll go back to get the horns, and have a look for water valves, etc. Must remember to grab the headlight mounting plastic bits too. Time for breakfast again! -- Jim
