1998 Mercedes-Benz CL420 (C140)
Discussion
Whilst chatting with Stegel and BM at the end of the Scramble I mentioned my climate control wasn't as cool as it had been. Stegel mentioned the diagnostic feature so off the internet I go. It blows cold air but never seems to keep the cabin cool on sunny days. I usually have to set at 19° or 20°C
My outside temperature gauge is faulty so it's bound to be a new sensor. £72 from MB and cheaper than most eBay sellers so that's to be ordered.
The right display has lost the two left vertical bars which is annoying.
Into the fault codes by switching on the ignition, set one side to LO and the other to HI. Press REST and recirc together and hold for 5 seconds.
One stored code for internal temperature sensor (b1227) and one for external temperature sensor (b1226). The codes start at b1226 so it is not b1225
I cleared the codes, switched the ignition off and on and only the outside temperature sensor error remained, which ties in with the above.
But if it's high then my logic would be that it should want to keep the car cold.
With the engine running and then set back to 19°C one presses REST for 5 seconds and it goes in to the live values. The pertinent ones are:
1 = internal temperature
2 = outside temperature
4 = right heat exchanger sensor
After a few minutes it settled down to a steady blow when the value of 1 = 23°C. The value of 2 = 20. If 2 = 20 then it must be taking the outside temperature from a different sensor and not the one from the gauge in the clocks. Hmm, the cabin still felt too warm
I incorrectly thought that the internal temperature sensor is in the centre vents below the parking sensor display but when I held my finger over it the value of 1 did not change.
Looking up in the roof console there is another tiny grille and holding my finger over that increased the value of 1 quite quickly to 30°C if I held it there. Removing my finger saw the value drop back down to 23°C.
I usually have my centre vents pointing upwards so I wondered if the sensor was reading the cool air and thus not making an effort to keep the cabin cooler. I moved the vents to point lower and sure enough the fan speed increased slightly and cooler air came out.
After a while 1 = 25°C and stayed there but with an increased flow of cooler air from the vents. I changed the control to 18°C and the value of 1 = 24°C. 17°C and the value of 1 = 23°C.
Is the system designed to have a 6°C difference between the control setting and the internal temperature? I don't know but it was consistent. Test results therefore are to try it with the vents pointing lower.
Just as I called it a day the right dash/door vent started throwing out very hot air which confused me. The value of 4 = 73, 78 or 79°C. I switched it off and went in for dinner.
My outside temperature gauge is faulty so it's bound to be a new sensor. £72 from MB and cheaper than most eBay sellers so that's to be ordered.
The right display has lost the two left vertical bars which is annoying.
Into the fault codes by switching on the ignition, set one side to LO and the other to HI. Press REST and recirc together and hold for 5 seconds.
One stored code for internal temperature sensor (b1227) and one for external temperature sensor (b1226). The codes start at b1226 so it is not b1225
I cleared the codes, switched the ignition off and on and only the outside temperature sensor error remained, which ties in with the above.
But if it's high then my logic would be that it should want to keep the car cold.
With the engine running and then set back to 19°C one presses REST for 5 seconds and it goes in to the live values. The pertinent ones are:
1 = internal temperature
2 = outside temperature
4 = right heat exchanger sensor
After a few minutes it settled down to a steady blow when the value of 1 = 23°C. The value of 2 = 20. If 2 = 20 then it must be taking the outside temperature from a different sensor and not the one from the gauge in the clocks. Hmm, the cabin still felt too warm
I incorrectly thought that the internal temperature sensor is in the centre vents below the parking sensor display but when I held my finger over it the value of 1 did not change.
Looking up in the roof console there is another tiny grille and holding my finger over that increased the value of 1 quite quickly to 30°C if I held it there. Removing my finger saw the value drop back down to 23°C.
I usually have my centre vents pointing upwards so I wondered if the sensor was reading the cool air and thus not making an effort to keep the cabin cooler. I moved the vents to point lower and sure enough the fan speed increased slightly and cooler air came out.
After a while 1 = 25°C and stayed there but with an increased flow of cooler air from the vents. I changed the control to 18°C and the value of 1 = 24°C. 17°C and the value of 1 = 23°C.
Is the system designed to have a 6°C difference between the control setting and the internal temperature? I don't know but it was consistent. Test results therefore are to try it with the vents pointing lower.
Just as I called it a day the right dash/door vent started throwing out very hot air which confused me. The value of 4 = 73, 78 or 79°C. I switched it off and went in for dinner.
Edited by tobinen on Monday 7th June 19:44
I knew it was possible to enter a diagnostic mode, but I didn’t know how, so I’m glad you gave it a go. There has to be some difference between the temperature selected and the temperature at which it tries to make a change, otherwise it would be oscillating between heating and cooling constantly trying to walk a narrow line, but 6 deg does seem a wide margin.
Climate control report: All was well about an hour into the journey back to Cambridge but then the right hand vent again started pumping out really hot air. Despite it being over 20°C outside the diagnostic still said 20°C so I suspect Stegel could be on to something and it has defaulted to that value. A quick trawl on the internet has a couple of ideas:
1. Set it to high and gradually reduce the temperature
2. It's a sticking mono/duo valve. Tapping it might free it.
I am driving back to Newbury tonight so I will try no.1 first.
MB Newbury has called and the outside temperature sensor has arrived.
1. Set it to high and gradually reduce the temperature
2. It's a sticking mono/duo valve. Tapping it might free it.
I am driving back to Newbury tonight so I will try no.1 first.
MB Newbury has called and the outside temperature sensor has arrived.
Tobinen,
I’m in awe of your perseverance with this CL (and with your now departed BMW).
I think many other owners would have thought “Sod it, I’m going to pass it on to someone else”.
It just seems to be one thing after another which is great for those of us who like reading of your exploits but it must be so frustrating for yourself.
I’m in awe of your perseverance with this CL (and with your now departed BMW).
I think many other owners would have thought “Sod it, I’m going to pass it on to someone else”.
It just seems to be one thing after another which is great for those of us who like reading of your exploits but it must be so frustrating for yourself.
I can happily report that no warmth was felt on the return trip. Everything stayed nice and cool. Perhaps it's an early warning sign so it's a 'monitor for now'
The spanner symbol is flashing so I checked the service book. I've done about 7,600 miles since the last one - in 2018. I'm due an A service so I think it will be a good opportunity to book in with Star and have the gearbox serviced at the same time.
Someone recommended MyAlloys in Basingstoke for the AMG IIIs to be restored. A quick search and it seems to have a good reputation and not too far.
The spanner symbol is flashing so I checked the service book. I've done about 7,600 miles since the last one - in 2018. I'm due an A service so I think it will be a good opportunity to book in with Star and have the gearbox serviced at the same time.
Someone recommended MyAlloys in Basingstoke for the AMG IIIs to be restored. A quick search and it seems to have a good reputation and not too far.
tobinen said:
I dropped off the wheels to MyAlloys in Basingstoke this morning for the refurbishment and return to silver. They should be ready Weds or Thurs next week. I am now shopping around for tyres though I have asked them to quote as it would be easier for them to fit at the same time.
Since you have the touring also, it won't be much hassle to cart them around for the best deal (assuming that they also don't tarnish the alloys). Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff