AC issues yet again - weird - PeachParts Mercedes-Benz Forum

#1 07-09-2002, 09:49 PM

My 1980 300SD has been going great. The air has been working well (in Las Vegas).

I just picked the car up from a shop where I swapped some computer work for oil cooler lines, and oil change, a transmission service and motor mounts.

Now the air doesn't work. Blows cool when I am driving fast, warm air otherwise. Blows hard, just not cold.

I think they must have done something unintentionally. Can someone help me with what.

dpetryk · #2 07-10-2002, 08:45 AM

Maybe they stole your freon.

leathermang · #3 07-10-2002, 09:09 AM

Dave, where is your faith in mankind ? Oh, you live in Houston ?, Nevermind

S Car Go · #4 07-10-2002, 10:46 AM

Pretty funny, leathermang. I used to live in Houston myself, so got a good chuckle from that one.
Dave, if the freon is entirely gone, why would the air blow cool when he's going fast? Just wondering...

leathermang · #5 07-10-2002, 10:52 AM

They were smart enough to leave some of it so it would not be so obvious ?

S Car Go · #6 07-10-2002, 10:57 AM

Dude, you've had your coffee this morning!

Wouldn't the freon blow cold no matter the speed, until it's used up? guessing, guessing...

leathermang · #7 07-10-2002, 11:29 AM

No, in fact that is the major description of systems not optimized for 134a... they do ok at speed but are iffy at slow traffic speeds... the amount of air going across the condenser really makes a big difference if the system is not up to par... so a system starting to get low on freon but not to the point of shutting the system down with the low pressure safety switch might exhibit these symptoms...But I am not the one that brought up the possibility they stole the freon.....
Another possibility,,,, particularly on these sometimes strange MB's is a vacuum line misplaced... some of these cars use the heater to modify the passenger/driver temps... and so the heater flap could be engaged where hot air is blowing... as compared to ambient temp air blowing... don't know if he was making that distinction in his description or not...

ok,, let me restate that first concept.... on 134 systems not designed to make up for the inherent lower efficiency of the 134 molecule and low efficiency 12 systems (due to low coolant charge)this complaint of low speed warm air due to the lower amount of air flow across the condenser at slow vehicle speeds is common.

S Car Go · #8 07-10-2002, 11:45 AM

Wow, that should give Monaco a thing or two to consider and check for besides theivery! Thanks for the info; beautifully stated. Folks sure can learn a lot here.

dpetryk · #9 07-10-2002, 12:26 PM

Well there has been a recent thread discussing events where freon theft has occured. Maybe they didnt get it all. Just a possibility. Its funny how it worked well before it went into the shop. S car Go where did you live in Houston?

S Car Go · #10 07-10-2002, 12:36 PM

Well it sure does sound like SOMETHING happened in the shop. I wonder how Monaco will approach this now!
Dave, I lived in a very soggy floody house in the northwest part of town. Great neighbors, though. Hope you aren't in a flood zone. Not good for your MBs!

The Warden · #11 07-10-2002, 12:52 PM

Quote:

Originally posted by monaco
Blows hard, just not cold.

Just wondering, how hard is "hard"? Maybe it's my imagination, but on my D, it seems to blow harder on DEFROST than it does on any other setting, even with the fan switch at HIGH.

I also have a problem with my a/c not blowing cold enough, but my electric fan's dead (just looked up the price on Fastlane and am wondering how hard it'd be to tear apart the one I've got and see if it's fixable) and I'm thinking I may not have enough freon...it's an R-134a system but doesn't cool very well during the day (even if it's just as hot, it works perfectly at night though)...

#12 07-10-2002, 02:54 PM

I am still on the old coolant for AC. These are the guys who fixed my AC on top of it. I took the car back today. We will see. They looked puzzled.

I've done compressor, evaporator, servo... everything basically. It was real cold.

I will post as I know what happened.

#13 07-10-2002, 08:15 PM

Another possibility,,,, particularly on these sometimes strange MB's is a vacuum line misplaced... some of these cars use the heater to modify the passenger/driver temps... and so the heater flap could be engaged where hot air is blowing... as compared to ambient temp air blowing... don't know if he was making that distinction in his description or not...

My 300-D had a similar problem. The air never really got cold enough, yet when my mechanic checked it the freon level was fine. He showed me an inexpensive trick to keep the heat from combining with the cold: get a little vise-grip wrench and crimp the elbow shaped hose near the firewall of the engine compartment. Be sure to wrap the hose with some electrical tape first. This will prevent any heat from entering the cabin, but you will no longer have any control over the temperature of the AC (it will always blow at the coldest temp). That method worked for me instead of a costly repair. To regulate the temperature I simply turn off the AC for a little while. Near winter, I'll remove the clamp and have heat as usual.
Hope this method isn't too unconventional and it helps. (BTW, my mechanic is pretty well respected in the DC area.)

#14 07-11-2002, 02:09 PM

I am waiting on a hose. The shop says that some freon was leaking out a 20 year old hose.

I moved the car from Vancouver to Las Vegas. I imagine I may be in for more similar problems. It is damn hot here every single day. The car is not used to that. I can see seals on doors etc. changing.

leathermang · #15 07-11-2002, 05:45 PM

WOW, that was a temperature shock move....

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