If i put in a little too much freon in will that cause the high side to get hot enough to switch on the fan or is it just that hot out? I'm working on two MBZs, the 280 SEL and a 240D. Hard part is the cheap 134A kits don't have the right fitting for the high side. The 240 is just not that cold of air coming out of the vents. I just had to add a touch of freon the the 280 SEL(Euro).

Any ideas?

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

Over charging the system will cause a higher head pressure and your system could blow at it's weakest point. Remember you mentioned retro fit. I take that the system was designed for R-12 which runs at a lower pressure than R-134a to begin with.

Hope This Helps!

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William
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1987 420 SEL - Like a fine wine only better with age

Yes, it IS that hot out. I have no experience with converted cars, but my R12 cars? The fans will come on just idling in the driveway.

BTW, technically it is pressure, not heat, that trips the fan switch for the AC.

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2012 E350
2006 Callaway SC560

On my recever dryer the feon does communicate with the freon directly. The sensor just mount to the dryer. I have a new switch and dryer, interesting enough the switch does not fit it. Small diameter threaded hole on the port and a larger diameter thread on th sensor. These ar parts that I've had in storage for years. The reciept is still in the box. They will fit something sooner or later. I think maybe I should deplete some of the freon out.

I just want to be cool, oh yeah way cool......

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

Just a thought here,

Since I still have R12 on hand, I haven't converted a car to R134A yet. But, I thought that the high pressure switch on the drier/receiver had to be changed to one with a higher cut-off pressure, since the R134a operates at a higher pressure.
Is your compressor shutting off too soon, or is it operating and not cooling very well.
Also, it was my understanding that the system requires approx. 80% of R134a compared to R12. So, if the system is overcharged with R134a, this could be your problem.
Please post the fix to your problem.

Good luck,

Dave

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Actually, it's the opposite problem. Retrofits are required to have a high-pressure cut-out switch, and your R12 system probably only has a low-pressure cut-out.

I did the 240D first as the system was apart for an extended period of time. I vacuumed the system for ever and filled it with the cheapy Walmart conversion. The first can went in ok, the second died during the install. I then used my gauge/manifold set to top it off. The cooling fan seamed to come on after only running a few minutes, leading me to believe the presures on the high side are just a bit too high. Cooling was not adequate during warm temps (95 degreees +). I thought the Walmart stuff may have had too much oil and it was plugging or semi plugging the condencer. So yesterday I isolated the condencer and gave it a good flushing out with alcohol and gave it a good mlow dry. Vacuumed down the system again and added about two and a half cans. The fans still come on pretty soon and really not cooling as well as it should. I bled out some freon this morning and it's plenty hot out now. I'm makeing a trip to the hardware store and I may let out a tad bit more and see what happens.

Hoping for a cool ride

__________________
1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

What does that mean?

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2012 E350
2006 Callaway SC560

The fan temp sensor is just that, it activates on temperature not the acual pressure. I noticed that once an a real hot day engine idleing the fan cam on, without the AC system being conected. Must have been pretty hot ambients under the hood that day.


Just got back from the hardware store Temp outside is about 100 deges. System seems to be putting out cooler air, no fan activated and more HP (for a 240D).

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

I don't know about your car, but on the 124/103 there are two sensors. One is in the head and it activates the fans to run on high speed based on temperature. The other is on the drier and activates the fans to run on low speed.

Any AC sensor on the drier which commands the fans to run is a pressure switch.

Of course, higher pressure equals higher temperature so in the big picture the effect is the same.

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2012 E350
2006 Callaway SC560

I am pretty sure that there is no switch in the low-side line, so that's not it. Check the high-side pressure to see if that switch is cutting out the compressor.