'93 500SEL AC Recharge Location? - Mercedes-Benz Forum

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Old 07-12-2008, 03:46 PM   #1 (permalink)
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'93 500SEL AC Recharge Location?

Hi all,

I recently acquired a 93 500SEL. It's in pretty good shape over all.

I was wondering if you guys could point me in the right direction.
I am trying to recharge the AC unit but I can't seem to find the valve on the low side.

Can someone please describe it to me?

I bought a kit, but have yet to see if the adaptor actually matches to the Benz.

Thanks in advance.
mb-maniac
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Old 07-12-2008, 05:46 PM   #2 (permalink)
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Hi all,

I found it but it didn't need a recharge after all. The AC still does not work however. I checked the switch on the reservoir and that works. However, the AC does not blow cold.
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Old 07-13-2008, 04:28 AM   #3 (permalink)
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Glad you found the low side a/c port. The high side is easily accessible too. Just open the hood and you will see the port lower right.
You have the same car I do and my a/c went out last week. Tried to recharge it. didn't work. Don't know what the problem is.
If you find the problem please let me know. Could be the compressor, expansion valve etc. These cars use 134a freon as opposed to r12.
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Old 07-13-2008, 06:27 AM   #4 (permalink)
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Quote:
Originally Posted by mb-maniac View Post
Hi all,

I found it but it didn't need a recharge after all. The AC still does not work however. I checked the switch on the reservoir and that works. However, the AC does not blow cold.
There are a couple of things that are easily done which can help you home in on the problem.

Firstly, check the sensor values by holding in the REST button for 20 secs. or so and read out the values in the RH display (see K6JRF Auto Page for details). You might also want to read out the diagnostic codes, as described in that link.

Secondly, check whether the compressor's electromagnetic clutch is staying energised. A few seconds after the car is started (with the A/C on) the A/C controller sends a signal to the base unit (a pcb under the hood) which then energises the clutch. You can see and hear the clutch pull in. An rpm signal is then sent from the compressor to the base unit and compared with the engine rpm signal. If these don't match sufficiently closely the clutch will drop out after a second or two.

See if any of this gets you a bit closer.

Good luck,

Mike

Last edited by MikeJT; 07-13-2008 at 08:31 AM.
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Old 07-13-2008, 07:55 AM   #5 (permalink)
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For those that find this thread via seach:

The low side on the drivers side of the underhood area, right behind the headlight assembly. You'll have to remove a cap (if not, put one back on!) and you'll know you have the right port because the rechage kit will fit onto the fitting (the high-side will not fit into the recharge hose). It is 134a, and my 500SEL took at least one can to get things cold again. It could still use some more I think. Also, I prefer to use the synthetic refrigerant.
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Old 07-13-2008, 10:21 AM   #6 (permalink)
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Thanks Everyone
I have yet to try the test, I will attempt it this evening and give an update later.

Thanks again
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Old 07-13-2008, 10:30 AM   #7 (permalink)
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Will it have any effect if you recharge through ONE connection, and not both ?
I refer to the connection under the plastic shroud on the left side of the engine-bay.
The garage couldn't see the other one at the left of the radiator. But said it wouldn't matter...
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Old 07-13-2008, 01:19 PM   #8 (permalink)
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Originally Posted by Eirik 400 SE View Post
Will it have any effect if you recharge through ONE connection, and not both ?
I refer to the connection under the plastic shroud on the left side of the engine-bay.
The garage couldn't see the other one at the left of the radiator. But said it wouldn't matter...
According to the recharge kits (I am not an A/C mechanic), the Low side/pressure port is the one used to recharge the system. The high side port is not used when recharging with an over the counter system available here in the US. So I would say charging though only one port is fine. I suppose with the proper equipment, the high side port may provide something additional.
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Old 05-10-2011, 02:58 PM   #9 (permalink)
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Hi All,

I am Having same problem with my 93 500sel AC, I have done DTC Test no codes,
When i got the car changed A/C Compressor, exp valve, receiver dryer, ac was fine for couple days then went warm air, all relays good, the only thing that is not is Comp clutch it does not cycle when turned on, how can i test the clutch to make sure its working ???
Thank J
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