My mechanic recommended I clean the condenser coils. I asked about using a non-acid foam spray cleaner from Home Depot that they sell to clean the coils of your home a/c unit, but my mechanic said not to get that, just clean out any bugs and just spray water on the coils to clean them.

Do you all agree? Seems like a foam cleaner would help it more.

FOAM!!!!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Guys, I read Brian Carlton's reply, about getting a thermometer to stick into the vent. He said he was getting 43 degrees out of his vents, which surprised me (I'm not a mechanic), I thought they only put out 55 or so if they were in good shape.

I don't have a thermometer, but I do have a laser thermometer gun. Assuming a normal thermometer would be stuck inside the vents, and give a reading where you could see it on the outside of the vent, I put my laser gun close to the vent, and reading inside there.

Believe it or not, the lowest reading, in the sweet spot, was 11.4 degrees!! Other areas it was about 17, 19, and if I went to the side vents, much different, I forget what it was, but maybe 45, since the air is further from the source. If I even pointed the laser dot at the outside of the vent, it was 25 in the sweet spot, and other areas were 34, 41, etc., depending on where the laser is.

Mind you, today's ambient temps were about 87 degrees.

So I guess the problem with Mercedes a/c systems is not that they don't get COLD enough, there's simply not ENOUGH of the cold! They need more volume of it, to take car of all the heat coming into the cars, by way of the sun's rays.

So clean the evaporator already!!!

Sixto
87 300D

My 300e (before evap ruptured) was putting out 38 degree air through the center vents while driving. at idle, it would go closer to 45-50 r134.

My w126 300se puts out 34 degree air out of the center vents, and at idle barely goes above 40. r12 refrigerant.

This would be at 80 degrees ambient.

Even at 100 degree days, the 300se would still put out 38-40 degree air at speed. At idle, it would suffer a bit.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

For the past few years, the AC in my 91 300TE (converted to r134 by PO) was only adequate at best, even with the correct r134 charge and pressures. So, I finally:

1. Pulled the dash and replaced all vac pods and rubber vacuum pieces.
2. Pulled the wiper and blower motor to clean the evaporator with HVAC coil cleaner.
3. Then I figured out the mono valve was not fully closing, so replaced that.
4. Had the r134 charge checked, and topped up.

Results, on original compressor and evaporator:
-July outside temps 95-102, center vent temps 58-62.
-August temps 80-90, center vent temps 48-52.

The 124 ACC system is complicated, and if just one component is off or bad, the system will not perform as we'd like.

These values are not correct. The infrared device is providing false readings due to varying reflectivity. If the air temperature ever drops below 38 degrees or so, the evap freezes. The system is designed to prevent this under all circumstances.

Go out and spend the $5.00 on a proper thermometer............like I suggested in post #11.

Buy a $10 mechanical thermometer.

Stick it in the air vent.

Then tell us the temp.

.

I see BC offers similar advice.

It's nice to see concurrence.

.

Yeah, my mechanic just emailed me the same thing, he said infrared gauges read way too low on a/c vents. Aside from this, my infrared gun has been very accurate around the house. I use it to detect heat losses, and I can tell quite well, where the insulation in the attic stops and where I need to put more.

Let us know what numbers you get.

.

Ok guys, I bought a proper temp gauge today. I didn't know that my infrared temp gauge would not give proper readings in a/c vents. That's strange. I wonder why? It's been AMAZINGLY accurate in many other areas around the house.

Anyways, I put it in, today's temperature was 91 degrees. There was no direct sunlight when I tested it, it was overcast. After 10 minutes of driving, most at 45 mph, the temp gauge only went down to 62. Mind you, the manual on the gauge says to test it in the shade, and I did not, but being overcast, it should have been a fairly good test. But that's roughly 30 degrees difference, which is pretty good, but maybe not great.

So now that we have an accurate number, what does that tell us? Brian was saying his went down to (cough) 43 or something. Wow. I didn't think a Benz could achieve that, ever. I forget what circumstances he said he got that under (temp, in sun or shade, etc.), but that is ... COLD.

62 is finally good data.

However, it's not satisfactory for cooling the vehicle. You've got to get it down to less than 50 if you have a prayer of decent cooling.

The issues can be low charge, insufficient airflow over the condenser (aux fan not working), or the evap temp switch is dumping the clutch much too early.

NEVER mix refrigerants.

My 1978 300SD is all original. I recently installed a new expansion valve and new compressor. I refilled the system with R-12. The auxillary fan comes on (cycles) when it is very hot outside, but my vent temperature is a very consistent 44°F on the road in 100°F weather and 48°F during prolonged periods of idle.

I have adjusted the ETR and produced 38°F in the vent, but felt the original setting of 44°/48°F was probably better for the system.

The nice thing about our '78 300SD is how hard the blower blows on Auto Hi. I think the amount of air it moves around makes it fell cooler than it really is....Robert

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Details.........details............!!!

On the W116, the Evaporator Temperature Regulator sits atop the evaporator case. If you pull the glovebox and use a 90° carburetor adjustment tool with a stright-blade screwdriver bit on the end, you can dig through a spot in the felt cover and turn the screw a little.

It is NOT easy to do!!!!

I don't recall now which way I went, but 1/2 turn dropped the center vent temp from 44°F to 38°F.

I went back to the original setting because I felt it would result in less strain on the compressor...Robert

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership