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please help, diagnostic code from radio regarding AC

1112 Views 11 Replies 4 Participants Last post by  mrboca, 
L
code 7 had a 0 0 reading and code 8 was an 84

does this mean there's no freon left

id like to put some in just to make sure it is even working correctly before i spend money on leak diagnostic. can someone point me in the direction of the fill connection?
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M
Was the a/c working before ? If it did , and you are just missing refrigerant, the chances are you just have a leak. I would skip the component testing, and go to some shop who is familiar with MB systems for leak testing.

You have the EC light ON and probably a bunch of fault codes which include the refrigerant fill. You can access those codes, as well as sensor readings (just as you did for #7 and #8) to confirm that the sensors are within range even if your a/c is not running.

To fill the a/c system with compressor not running (EC light ON) you need to reset the codes from the fault code menu and restart the car with the a/c on. If you insist on checking the system, a can (12 ounces) may be enough to keep the compressor going for testing.

The shop should know how to reset the EC light to get the compressor started prior to fill with refrigerant + dye.
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M
The 419 code refers to an electrical issue with the compressor clutch, either the clutch coil is open, or a wiring / connector problem.

To confirm, you can take a resistance measurement between the chassis and the a/c controller connector pin for the clutch control.

You can also apply fused 12V to the compressor clutch connector briefly (and chassis ground) to check the operation of the clutch.

Normally, the compressor in your car does not cycle. When you select a/c cooling (EC button LED off), the clutch / compressor is engaged all the time. Pressing EC button (LED ON) will disengage the clutch.
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M
You need to get the clutch engaged to find out whether the compressor is running.

Possibilities:

1) Your clutch does not engage continuously or intermittently due to a problem detected by the a/c controller. It could be a wiring or connector corrosion issue (the car sat for a year). If this is the case, the chances are your compressor is fine (but you have a leak somewhere)

2) Your compressor seized up, and caused the thermal fuse inside the clutch coil assembly to prevent the drive belt from destroying itself. In this case you need a compressor plus dryer, and very likely condenser and expansion valve (due to crud from broken compressor). This would cost you north of $1,200, depending on the workshop. As you do not know where the leak is, and how bad it is, it may require other replacements too. If the evaporator is leaking, that would cost a lot of money, as the dash needs to be removed.

3) If you cannot test the clutch by applying 12V yourself, find a some reasonable technician who can do it for you, and tell you whether the compressor can be engaged. Once it can engage and running, you can check whether #7 is rising to 12 for example. If #7 is not going up much when the compressor is running, the chances are the compressor is bad.
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