Thanks to the forums I have run the onboard diagnostics for my A/C that is not blowing cold.

My ECT sensor #6 is reading E. I cannot find a part # for this sensor and have not been able to find out if it could be causing my compressor to not turn on.
Sensor # 7 reads 6 bar.

Can some one please help with the ECT mystery??

Other codes are 1234 sun sensor
and 1227 outside temp sensor
I don't think either are critical for this problem since so many others report
these same codes with working systems.

My EC light was on, and would not turn off until clearing codes and adding 16 points to the right side temp 136 to 152. After a couple of restarts the EC light is now off however as before compressor will not kick on to take more R134. Car is super low mileage at 33k

Thanks and Aloha

The ECT sensor says error - that means that either the sensor went bad or the HVAC unit cannot see it (wiring problem) - Its the engine coolant temperature sensor and is available quite easily too.

Its right next to the upper radiator pipe outlet on the engine and has an angled head.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

thanks, I located the sensor and am still wondering if its malfunction can prevent the compressor from kicking on. Does anyone know?

If the engine overheats it can, not sure of the error "E" message. Is one of the codes you have related to ECT? YOu only mention codes for the outside temp and sun sensor.
One sore spot is the evap temp sensor, and for awhile there was a problem with the refrigerant level sensor, which MB had the dealers deprogram, but I think this was later 1990s.

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My car is not overheating or running weird. Just the A/C compressor not kicking on. Many owners have reported code 1231 (ECT sensor) when running diagnostics for A/C not blowing cold. No one mentions replacing this sensor as solving their problem, or the part #. Online OEM part sellers have no code fault knowledge and ECT sensor is not something that means anything to them.

Can someone provide some useful information here please?

Do you have a fault code in engine management for the ECT sensor?
None of my prior questions were answered either.
Want to help but you have to be a participant as well, sorry if your answer is not easy to produce, we all just try to help here.
MORE than likely it is too low on refrigerant for the compressor to engage, but that is a generalization. Has anyone put gauges on it?

The main thing that will keep the clutch from enagaing is refrigerant pressure too high or too low or if the serp belt is identified by the compressor as slipping. Is the belt tight?

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Yes Gilly, second line first post: My ECT sensor #6 is reading E for error.

Thanks

I have ordered this sensor from Pelican, parts department (Ken) knew this sensor and DEFINITELY will post whether
this cures the problem. It would be extremely useful if it were common for others to post the such results and whether they work or not. And yes I have checked the other obvious things you mentioned, this is a highly maintained car and looks as new... 33K only

I have spent several hours searching 3 forums for an answer to this issue, with this specific code 1231, as it is very commonly found in no compressor / no A/C problems... Should know the answer by the weekend.

Aloha

when my w210 A/C conked out it was the magnet on the compressor pulley, its thermal fuse had burnt out.

The way I verified it was with a multimeter after reset of the climate control unit. The compressor magnet wire was reading 14V when it was switched on but I had no compressor activity.

When I ohmed it out the resistance was in megaohms. New clutch assembly solved it. Lesson learned is that the clutch pulley gap should always be in perfect range otherwise the pulley chatters and overheats eventually blowing the thermal fuse.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Zulfiqar, thanks for the heads up on the sensor location just to the left of water pump by upper radiator hose. Its an easy replacement. I did it by first removing whatever that blower assbly is just above the sensor so it would be easy to get the retaining clip off and back on. Can be done in 10 minutes total unless you are a clean freak like me and have to carefully clean everything exposed...

Will run the tests tomorrow to see if code is cleared and if it affects the A/C and report back...

Code # B1 231 still showing up after replacing sensor with Pelican OEM Mercedes part, and clearing codes

Tried this several times and it has no effect whatsoever on A/C compressor problem. There are no other odd sensor values or codes of relevance.

Very disappointing...

EC light isn't on is it?

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HELP! 97 E320 W210 Aux Fan Not Working

I read this entire thread, and understand much of it. You are a real expert, and may have seen a set of issues like these. I am happy for pay for expertise. WDBJF65J52B454614 only 36K

My problem is similar except that instead of no aux fan operation, my aux fan howls as soon as the car is running.

History of problem:
1) no A/C
2) ran on board dx finding multiple A/C related sensor codes
3) replaced all sensors and cleared codes

Had the system evacuated and refilled showing 7 barr pressure without engine running.

Below is the history on this problem and my attempts to solve it:

I ran the on board diagnostics for sensors and fault codes as follows:

B1232 refrig pressure sensor
B1233 refrig temp sensor
B1227 outside temp sensor
B1231 engine coolant temp sensor

I replaced all 4 of these sensors and also the evaporator sensor (never had that code) but still have two codes that will not clear: B1227, never had incorrect readings on dash, and B1231, never had any overheating

Oddly after problem began I notice the night time illumination bulb in the HVAC is out and remains out even after replacing the bulb...

Sensor values are as car warm but not running as follows:
1 87 Inside car temp sensor
2 E Outside temp sensor (replaced)
3 87 Heater core L
4 87 Heater core R
5 89 Evaporator temp sensor (replaced) though it seemed normal
6 E ECT sensor (replaced) still shows E
7 07 bar refrig pressure sensor (replaced)
8 100 refrig temp sensor (replaced)
20 control current for aux fan 6.7

Compressor will not engage, has 7 bar pressure. Direct 12V to compressor and she blows cold. No blown fuses having anything to do with A/C, #5, #7, #20 or any in the fuse box by the brake booster. I swapped some fuses to be sure they were good. I found no direct compressor or clutch fuse in the box. Have not been able to find the function of relays in back of fuse box.

The engine cooling fan starting running all the time on high, probably because it thinks the car is overheating due to ECT sensor fault, so I unplugged fan. Located the Aux fan control unit under drivers headlight area, thought about changing it since its a known issue with these cars but never read this helping anyone with the fan howls only the fan won't engage issue.

Never any overheating. Checked the old ECT sensor in hot water with multimeter and it responds). I suspect this fault could also be the reason the compressor clutch will not engage.

When the problem began the EC light was on but I was able to get it to go off by changing the value of the computer by 16 points in an attempt to get the compressor started. It has not come back on since even after changing the value back to original.

Here is how I got the EC light to go out:

1. Switch the ignition on (position 2).
2. Set the left temperature to 'HI' and the right temperature to 'LO'.
3. Switch the ignition off.
4. While holding the 'REST' button, switch the ignition on (position 2). On the left side, 'P1' will flash and on the right side, a code will be displayed.
5. Press the 'EC' button twice so that the left side flashes 'P2'.
6. Using the right side red temperature increase button, add 16 to the value.
7. Press the 'EC button again to store the updated code.
8. Turn the ignition off.

I have since changed the value back to original settings.


Can you possibly help? I am very happy to pay for expertise.
We have no Mercedes Indy shops here in Maui Hawaii.

All the best,

Paul

sorry for cross posting but this fix has the potential to help someone else with
these ridiculously complicated HVAC systems that can cause FALSE sensor codes, turn your radiator fan on high, and prevent your A/C from working!!

AUXILIARY FAN CONTROL MODULE 0275457732 - Mercedes-Benz Forum