Yet another senseless A/C question.

[Zerohour3k]

Okay, it's summer, and I'm sure everybody is loving their AC. I recently got mine repaired, but I wanted to asked the "Hive mind" here what they think about a few things.

First and foremost, the wiring job that was done, bypassed my 0-Max dial. Whenever I click on my blower, the A/C engages. Obviously, I will need to fix this, since there's no way I want to be running the compressor year-round at full-tilt. I suspect it's a bad relay somewhere (and I'm going to need to re-crimp a wire end that was cut off under the engine bay).. but does anybody have a wiring diagram of the 84 "euro" style climate controls? For a better idea, see my shopforum gallery for a pic of my setup.

Second, the A/C itself. Granted, I don't expect the sucker to be blowing icicles during a 98+ degree heat wave, but I do expect it to be at least as cold as it was when I had it working a year ago, since aside from the evaporator and condenser, everything is new. The system has been charged with R-12, and blows cold... sort of. The problem? Well, it's a two-parter.

* During the morning commute, when temps are relatively cooler outside (let's say... 85-89 degrees F), the system fires right up and practically gives me frostbite. I don't know if it's a problem or not, but the center vents actually blow "smoke" after six minutes or so. I take it on the highway, and it continues to do its job the same way, until I hit the "fifteen minute mark". Things go downhill from that point, and the side vents blow cool / WARM air, and the center vents (while still 'smoking') are substantially cooler. I used a laser thermometer and confirmed that the vents are definitely 5-10 degrees warmer. This issue occurs at almost any speed, during both the morning and night (I took a scenic route on Sunday, and drove around for an hour or two through a road less travelled, @ about 50-55mph. Same issue.)

* During DAY commutes, is where things get painful. My passengers complain constantly, since the AC simply isn't doing much of a good job. Granted, my car is black.. but it was black two years ago, but definately a lot colder. Now, when the temp is 98 degrees out, and I turn the car on for the first time, I don't expect a miracle. Turning on the AC will make the center vents blow at ~65-69 degrees, and the side vents at 72-77. This is on local roads. Hitting the highway, they cool down a bit more, but never really get past the 45 degree mark. This same A/C system a year ago was fine in 100 degree weather, and literally froze out my passengers in the back seat, what would cause it to be so substantially different? Same rule as above, applies. Once it cools down to "cold" temps, it doesn't take long before the sucker warms back up to "cool" temps.

On hot days, the engine with the AC on runs at about 96-100C, (the mark above the middle on my temp gauge).. but I'm guessing this is normal, since it tends to run at 86 or so on local roads / anything less than 60 mph.

Thanks in advance for any advice, guys!

[vstech]

in order to diagnose refrigeration issues, we need inside, outside temps and high and low pressures. and RPM of engine when testing pressures helps too.
when you say you replaced everything but condenser and evaporator, did you replace expansion valve? do you have any leaks? have you confirmed no leaks with a 200 psi dry nitrogen hold test for 24 hours? did you completely flush out the system prior to compressor/reciever changeout? did you fill with the correct amount of oil with the compressor? what condition is the aux fan in? does it actuate with the pressure increase? report back.

[Zerohour3k]

Outdoor temps are typically around 85-98 degrees Fahrenheit. Indoor temps (aside from that morning commute, which ambient temps are usually lower in), are... "cool" at best. Sorry, I don't carry a thermometer with me, heh

The A/C job was done professionally by my mechanic, who has done good work in the past. I'm assuming the expansion valve was replaced (since it's fairly commonplace to replace those when doing an AC recharge / repair). He's checked for leaks twice now, and there isn't a drop of freon leaking out. Low pressure side is in-check with what it should be.. and the high pressure side isn't accessible on my stupid Volvo compressor, so it is untested.

Aux fan works without a hitch, and both the temp switch and pressure switch are brand new. The fan cycles when the temps get too hot (usually doesn't cycle on unless I'm sitting in traffic, or driving 80mph in 100 degree weather, which tends to overheat everything anyway. And no, I don't drive 80 normally. ). Pressure switch works, as well. As far as I know, everything is in-check when it comes to oil / refrigerant levels, and no "white smoke" or bubbles can be seen in the sight glass of the dryer.

[vstech]

sorry, still need pressures with temps to verify system operation and chart a course to correction. also "assuming" that some parts were changed, is dangerous. just as dangerous as assuming the system was cleaned. get a list of parts that were replaced, and verify them yourself. sorry your system is not working, but it sounds like your "mechanic" didn't do such a great job.

[vstech]

since you have "cool" to Warm air exiting the side vents, you could have a vacuum issue allowing warm air or outside air to mix in with your working a/c system. that would be my next path to follow.

[Zerohour3k]

Originally Posted by vstech

since you have "cool" to Warm air exiting the side vents, you could have a vacuum issue allowing warm air or outside air to mix in with your working a/c system. that would be my next path to follow.

Unfortunately for me, I don't think this is a vacuum issue. Mostly because, well... the entire AC system in this car is manual.

Like I said, he's done great work in the past.. so I trust that he cleaned the system / did proper procedures.. but at the same time, you're right. Truth be told, the A/C isn't blowing as cold as it should be, and the dial / wiring that WAS working last year, is now obsoleted? I dunno, for the money the repairs cost, I'm not exactly a happy camper with this system right now...

[vstech]

Hmm, I have not followed the system in my euro, so I don't know exactly how everything works, but I think the heat vents can get knocked loose and allow mix air to throw off the cooling. something is certainly happening after 15 minutes, so ya gotta start somewhere. sorry you are having problems with your tech.
John

[dmorrison]

Sounds like your mono valve is leaking. As the car warms up it allow the heater core to become filled with hot water. Diluting the cool air with warm air. And the vents get warmer. I would check the mono valve and see if the unit inside is torn. If so replace it and see if all works OK. Also chack the voltage at the mono valve to see what the AC conrol unit is sending it.

Dave

[Zerohour3k]

Originally Posted by dmorrison

Sounds like your mono valve is leaking. As the car warms up it allow the heater core to become filled with hot water. Diluting the cool air with warm air. And the vents get warmer. I would check the mono valve and see if the unit inside is torn. If so replace it and see if all works OK. Also chack the voltage at the mono valve to see what the AC conrol unit is sending it.

Dave

You know, this makes a HECK of a lot of sense, now that I think about it..

Looking at the facts, I see:
*The car had working AC last summer, and it was bloody COLD too. It had a dial that allowed me to control the coldness of the AC, and to turn the compressor off.

Now, my mechanic snipped a bunch of wires, re-wired under the hood, and essentially bypassed my dial / relay. What probably happened, is that that dial sent voltage to the monovalve as well as the compressor. A relay engaged under the passenger kick panel which would in turn, engage the compressor. I'm guessing the dial not only accomplished that, but it PROBABLY was a variable voltage regulator for the monovalve as well, thus pumping cooler / warmer air into the car, based on my settings (or turning OFF the compressor when I chose to do so).

Unfortunately, I'm going to have to fix the wiring under my hood (since it was rigged to operate in a completely different fashion, now), and fix the relay under the kickpanel. With those two things working, I'm willing to bet the AC will blow the way it's supposed to.

Thanks for the awesome idea, though.. I was never sure how the monovalve worked! Can using it without voltage damage the valve? Or will it just pump hot air into the car?

THANKS!

[TimFreeh]

Originally Posted by Zerohour3k

Now, my mechanic snipped a bunch of wires, re-wired under the hood, and essentially bypassed my dial / relay. What probably happened, is that that dial sent voltage to the monovalve as well as the compressor. A relay engaged under the passenger kick panel which would in turn, engage the compressor. I'm guessing the dial not only accomplished that, but it PROBABLY was a variable voltage regulator for the monovalve as well, thus pumping cooler / warmer air into the car, based on my settings....THANKS!

Uh... Yeah sure.

The compressor is turned on and off based upon the temperature of the evaporator - and the compressor should cycle on and off to maintain whatever temperature has been set on your "0-max" wheel.

If your "mechanic" hard-wired the compressor to be on 100% of the time it would take about 10-15 minutes for your evaporator to turn into a gigantic block of ice. The ice would restrict the flow of air through the evaporator core and cause A/C performance to drop off significantly.

You mentioned that the A/C performance starts to fall off after 10-15 minutes - next time this happens turn the A/C off for 20 minutes to give the evaporator a chance to de-thaw. Then turn on the A/C again, I'm betting it will work fine for another 10-15 minutes until the evaporator freezes up again.

[ytr1903]

Does a manual Euro system even have a monovalve? My gut says that it does not, but my brain says, "Shut up and stay out of the discussion."

Tom

[Zerohour3k]

Originally Posted by TimFreeh

You mentioned that the A/C performance starts to fall off after 10-15 minutes - next time this happens turn the A/C off for 20 minutes to give the evaporator a chance to de-thaw. Then turn on the A/C again, I'm betting it will work fine for another 10-15 minutes until the evaporator freezes up again.

You are correct, in this.

The other day I was on a long stretch of road going 55mph. A/C blew cold for about 25 mins or so (it was cool outside), and then performance went WAY downhill. I turned off the A/C, and drove with the windows down for about 10-15 mins.

After deciding "Okay, it isn't *THAT* cool out" and putting my windows back up, I switched my A/C back on. Lo and behold, it was blowing freezing cold air again. Even weirder, an ICICLE flew out of my left vent and hit me in the chest.

Could it be a combination of a broken / non powered monovalve *AND* the fact that the compressor is hard-wired to run non-stop (thus turning my evap into a brick)? Like I said, my guy is pretty good with just about all the other jobs I've taken to him.. but he isn't really sure when it comes to the Euro systems, I guess. (no wiring diagram)

If I can get a relay and a bunch of wire to fix the snipped one, I should be able to get this puppy working the way it's supposed to!

[Zerohour3k]

Originally Posted by ytr1903

Does a manual Euro system even have a monovalve? My gut says that it does not, but my brain says, "Shut up and stay out of the discussion."

Tom

I'm just as clueless as you on this question, but I assume that all the Euro systems are different, since they were aftermarket add-ons. Of course, I could be totally wrong on that.

[autobahnauto]

I figured I'd add my two cents. To be sure the system is working properly, I would have your tech add a high side port to the line between the receiver drier and the condenser. This way you can ensure the fan is coming on at the correct pressure as well as make any cooling diagnosis easier for the tech. The monovalve makes sense. Be sure that you are quoted for the monovalve repair kit and not the complete monovalve. Just about anyone with a screwdriver can replace the repair kit with ease.
Most shops won't touch the Gray market cars due to the differences. Unfortunately, when I started working at my shop before I bought it, we were the only place to take a gray market car and serviced plenty of them. The a/c systems are not a fun thing to work on when they are added on after the fact, but with a little patience everthing should work out fine.
Let me know how you make out and feel free to call me if you need to.
Dave

[Zerohour3k]

Brief update for anybody interested in the fix.

After looking over the wiring, I realized it was the exact same system as a 80 / 81 240D. I bought another relay and stuck it under the passenger kick panel, hit the center "AC Dial" switch with the blower on, and.... nothing. The A/C wouldn't turn on, however there WAS another relay that clicked over somewhere under the dash.

Anyway.. after some more pondering, I dove into my spare parts pile and pulled out three spare dials. The first one didn't work at all (it was my original dial that came with the car), but the second one engaged both relays (new one and the "hidden" one, which I'm guessing closes the monvalve). From there it was just a matter of checking if the snipped wire under my hood was pumping out +12v (it was), and sticking it on the front relay.

Thanks for all the help, guys! Finally got this puppy working with the dial again, so that I can use vents without the AC.

Now.. anybody know anything about "refurbishing" these old dials? All the resistors appear to be OK on them..