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AC problems please help!!!

3K views 48 replies 6 participants last post by  roadrosen 
#1 ·
Hi I have a 98 Mercedes e430 and the ac blows hot then cold off and on but more hot then cold! I had the system drained and recharged at a shop and changed the evaporator temperature sensor but still no luck! Please any help is appreciated!!

Error code eb1235

Sensor values

1-111
2-123
3-123
4-121
5-118
6-202
7-11
8-127
9-27
10-0.8
11-4.3
12-4.2
20-3.2
21-32
22-00
23-32
24-11.8
40-164
41-32
42-72
43-152

Please help its summer time here in Hawaii and I can't stand this heat!!!
 
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#3 ·
Hello,

Do you have the values when the engine is running at operating temperature with the a/c on "LOW" on both sides ?

Above, item 24 (11.8) indicates that your engine is not running. The battery voltage should be around 13.2 to 13.5V, in item 24.

If the engine was running, then your battery is not charging.
 
#4 ·
Hi I have a 98 Mercedes e430 and the ac blows hot then cold off and on but more hot then cold! I had the system drained and recharged at a shop and changed the evaporator temperature sensor but still no luck! Please any help is appreciated!!

Error code eb1235

Sensor values

1-111
2-123
3-123
4-121
5-118
6-202
7-11
8-127
9-27
10-0.8
11-4.3
12-4.2
20-3.2
21-32
22-00
23-32
24-11.8
40-164
41-32
42-72
43-152

Please help its summer time here in Hawaii and I can't stand this heat!!!
Hello,

Do you have the values when the engine is running at operating temperature with the a/c on "LOW" on both sides ?

Above, item 24 (11.8) indicates that your engine is not running. The battery voltage should be around 13.2 to 13.5V, in item 24.

If the engine was running, then your battery is not charging.
This is the values with the car running and ac was actually cold

1-96
2-138
3-60
4-58
5-57
6-199
7-17
8-134
9-39
10-6.0
11-3.8
12-4.3
20-12.7
21-42
22-00
23-32
24-13.5
40-164
41-32
42-72
43-152

Thanks
 
#6 ·
This is the values with the car running and ac was actually cold

1-96
2-138
3-60
4-58
5-57
6-199
7-17
8-134
9-39
10-6.0
11-3.8
12-4.3
20-12.7
21-42
22-00
23-32
24-13.5
40-164
41-32
42-72
43-152

Thanks

Looks fine when blows cold.

1) When you say blows hot and cold, does it do this when you set the temperatures to LOW at both sides, or just when you set the temperature to say 70 degrees F ?
2) Does hot air blow from both left and right central vents ?
3)When it blow cold, does it blow cold about the same temperature from left and right vents ?
4)Does it blow warmer when you are idling at traffic lights?
5) When the engine is cold, and you start the car with a/c on, does it blow cooler than when the engine is at operating temperature ?
6) Does the hot / cold blow flip flop at certain rate or. random ?
 
#13 ·
Duo valve holds when it is cooling, the issue is does it hold when it is NOT.

If you see the same sort of temperatures in 3, 4 and 5 when it is not blowing cold, one would say it is not likely a duovalve problem.

I think the error is for the smog sensor. How will it affect the air cooling if faulty ?

I thought it was for air routing to recirculate when Carbon Monoxide detected ?
 
#14 ·
As you said, if pollution sensor triggers the alarm, it diverts the flow to recirculating via carbon filters.
But recirculation can be run only for limited time, or driver will die from lack of oxygen, so who knows what MB programmers made up for such situation.
Than if the sensor was read faulty, the computer has default programs for such occasion.
Problem is that defaults programs are unknown to car owners, so we can only guess or try by error.
My logic guess would be that with pollution sensor failure, the computer will "nag" the owner to take care about it... like killing AC for example :D
 
#22 ·
Are you saying that the intermittent hot air blowing through the vents is not happening, and you are just having very cold air when the car moves but not so cold when the car is idling ?

You get very cold air regardless the temperature setting (after the interior reaches the desired temperature ?

Are you sure you installed the right part, and installed correctly ? If not. your evaporator can freeze over, and you get hot air due to reduced surface transfer. For example if your evaporator "actually" goes down to 32 Degrees F, but your evap sensor say it is 42, the compressor will keep on running till finally it catches up with the evap. temp sensor.
 
#21 ·
Maybe I miss something, but the 2 readouts you posted did not indicate any problem with evap temp sensor?
I still would advise you to check the pollution sensor, as we don't know how the error can affect AC performance and at this point that seems to be the only thing that can occasionally kill your AC.
The sensor is located somewhere under passenger side gutter, but I never had to see it.
Hopefully it is just dirty plug, so have can of MAF cleaner with you.
 
#24 ·
So you replaced the sensor only becouse somebody else did on different car?
Again, from your data did not look that sensor was bad and if AC started to work better it could be coincidence, or something else you did not even knowing.
I think you will never figure it out till you do proper troubleshooting.
 
#27 · (Edited)
I wonder if your engine speed sensor #21 (rpm x 100) could be causing the problem. Wouldn't it shut down the compressor if excessive engine speed is detected (obviously your engine isn't spinning @ 440,000 rpm)?

10 bars (#7) @ 107 degrees (#8) would indicate compressor is off if system is charged correctly.
 
#30 · (Edited)
In post #3 , Mr Boca stated engine was OFF when you did your FIRST reading of values based on #24 indicating battery voltage was at 11.8 volts. Yet #21 shows 32 or engine speed of 3,200 rpm! Values should be read at idle as I previously posted with a link on how to do it correctly.

I'm not positive but pretty sure there is a rpm cut off for the compressor. If your #21 sensor is giving sporadic high reading, this could be your problem.

BTW: I edited post #27 . Your compressor was off during last reading of values.
 
#31 ·
Yes that is what I was going to suggest that you check.

The RPM is derived from crankshaft position sensor signal to the ECM which is the supplied to the instrument panel, which is then passed to the climate control unit. It is used to determine when to turn the aux fans on (at idle, and how much, based on the refrigerant pressure sensor. If the aux fans do not run at idle the condenser will not cool the refrigerant and reduce the pressure. When you are at highway speed the fans do not need (and should not be) to turned on due to incoming air flow..

The climate control seems to send the voltage to the fan control unit but maybe the unit is faulty or the fuse is blown. Or maybe the fans are not working as they should.

I would check the fan operation and fuses..
 
#41 · (Edited)
Hi I have a 98 Mercedes e430 and the ac blows hot then cold off and on but more hot then cold!
^^^ I assume OP means air conditioner is working sporadically.

Ok so since I've changed the evap temp sensor the ac blows cool/ cold now as soon as car warms up. Now what I'm noticing is it only blows super cold when the car is in motion.
^^^ This sounds normal. Air conditioner does not engages immediately after start up (there is a delay). Air temperature will be colder when car is in motion because there is more air flow thru the condenser and compressor will be turning faster with the higher rpm.


Now the air blows cool/cold all the time just noticing now it blows colder when driving on the freeway for example.

Sorry if I'm confusing everyone just explaining the symptoms as they come
This statement is confusing. Is OP now saying air conditioner is no longer operating sporadically and is on all the time? As stated above, air temperature will be colder with car in motion.
 
#46 ·
Does your car cool well when cruising at 60 miles/hour ?

If so, , it does not seem to be affecting the compressor operation.

for emissions sensor, see attached. The emissions sensor just changes the way airflow is routed (recirculating air through the charcoal filters).

If I were you I would do the following:

1) reset the climate controller when engine is off by taking its fuses off , wait few minutes and reinstall them

2) Check the connector on the compressor for the compressor clutch. If the connection is intermittent due to contamination / corrosion, you may have intermittent clutch disengagement which would cause the compressor not to work. I am not sure if this would be detected as a fault eventually.
 

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