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2007 SL550, 1996 E300 Diesel, 1959 220SE, 1965 Unimog 404.115-Sold
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Discussion Starter #1
I have a 1996 E300 Diesel that at the beginning of last summer I replaced the A/C compressor, Condenser, Receiver/Dryer, and Expansion Valve and had the system evacuated and charged and the A/C worked fine all summer. This summer it was also working fine until about a month ago when it started to not be as cold as it should and I still had a can of R134 left over from last year so I installed the can and it was good again for a week or so and then went warm. After looking at all the connections in the system I noticed oil build up on top of the receiver dryer so I replaced the o-rings on the pressure switch and on the line going to the evap and charged it up after installing some leak detector dye. The system lost the charge right away and using a black light I could not find any sign of a leak. I ran the diagnostic and it had a code of b1232 pressure switch so I purchased a new switch from the dealer and tried to charge the system but it would only take about a half can of freon and the compressor came on but the air was hot. After checking for leaks again and not finding any I took it to the local garage and had the evacuate it but they said it would not evacuate down very much due to a leak. I cannot find any leaks and I still have the b1232 error code. I'm hoping somebody else has dealt with this issue and might have some direction for me to look at?
 

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2001 E430 4matic
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419 Posts
Ok now, after reading this 3 times, I think I finally got it (I think) :)

Final step, after changing the pressure switch your system was not charged properly. You went to evac and obviously not much there as they told you. Seems like you should recharge your system using evac/ refill with sealant and dye if you can. IF, after that you still loose refrigerant, check the expansion valve, and evaporator drain. Remember to delete all the fault code just before recharge! At this point after repairs that you have done, you can not be sure that system is working since not been charged.

Good luck.
 

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E320/E250 Bluetec Ford F350 6.7l
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If the dye did not show anywhere that points into the evaporator, what is big pita to replace. I used sealer on mine in desperation and it is holding 2nd season.
 

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Registered
2007 SL550, 1996 E300 Diesel, 1959 220SE, 1965 Unimog 404.115-Sold
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311 Posts
Discussion Starter #4
Ok now, after reading this 3 times, I think I finally got it (I think) :)

Final step, after changing the pressure switch your system was not charged properly. You went to evac and obviously not much there as they told you. Seems like you should recharge your system using evac/ refill with sealant and dye if you can. IF, after that you still loose refrigerant, check the expansion valve, and evaporator drain. Remember to delete all the fault code just before recharge! At this point after repairs that you have done, you can not be sure that system is working since not been charged.

Good luck.
I took it to the shop to have it evac & charge and they could not evac as it has a leak. I replaced the expansion valve last year but am willing to replace again, but don't know how to tell if it is working or if it has a problem? When you say check evap drain do you mean the water drain under the hood? Or is there another drain somewhere else? Thanks
 

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2007 SL550, 1996 E300 Diesel, 1959 220SE, 1965 Unimog 404.115-Sold
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311 Posts
Discussion Starter #5
If the dye did not show anywhere that points into the evaporator, what is big pita to replace. I used sealer on mine in desperation and it is holding 2nd season.
Yes I was thinking the evap may be leaking also. But shouldn't I be able to see the dye coming from the A/C vents if the evap is leaking? Thanks
 

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2001 E430 4matic
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419 Posts
Now that mis-understandings are cleared its easier to troubleshoot.

This is what I will do:

- Open the plate under the windshield wiper and see if you could see with your light any leaks. (If you see, you found your problem)

- If no leak, the next suspect is your evaporator.

- (not my favorite method in all cases, but if saves few grand not changing evaporator, I suggest this) get AC sealant, dye, refrigerant (delete the faults) and charge the system as usual and pray to Lord that system to hold the pressure, if not, most likely is your evaporator. You should see leaks under the car (under transmission) if evaporator leaks.
 

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E320/E250 Bluetec Ford F350 6.7l
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Some members report evaporator leaks showing dye under front carpets. I put big can of dye and had clean carpets.
Small leaks will not show any fumes via the vents, while the big one that would, should also hiss compressed air.
 

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2007 SL550, 1996 E300 Diesel, 1959 220SE, 1965 Unimog 404.115-Sold
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311 Posts
Discussion Starter #8
I appreciate the help. I will try these ideas and hope my evap is not leaking.
 

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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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1,915 Posts
Evaporator sounds like a culprit. However, food for thought:

When you replaced the expansion valve, did you replace all of the O-rings? (They are a pain to get out and reinstall)

Were all the other O-rings replaced? When replacing the O-Rings, did you use PAG oil to lubricate them first? Correct torque applied? Did you black light all these connections?
 
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