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MB CLS550 -09, MB SL600 -94, MB 560SL, MB 170s, Austin Healey Sprite
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834 Posts
Discussion Starter #1
I have a CLS550 2008, 5,5l m273 imported from USA, with some strange heating issues, started with intermittent heating (in Sweden you need heating). The heat came and went without logic, I replaced the "Heater Control Valve" underneath the windshield, that made the heating consistent at least. Currently it works 100% when engine idles or above (exact break point) 2000 rpms, anything between idle and 2000 rpms=no heat.

My best guess would be the thermostat, but symptoms doesn't fit 100% as far as my thinking goes, does anyone have any pointers or suggestions?

I don't seem to have any fault codes.
 

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W219 320CDI -07 W220 320CDI -01 W210 270CDI -01 EX: W211 320CDI -04
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1,021 Posts
Have you checked amount of refigerant? (my 2nd same advice at short time lol). My C219 (imported from Sweden! :) ) was blowing only lukewarm from middle and kept whistle noise which changed when turning. I changed also water valve but true reason was lack of freezer fluid.
 

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MB CLS550 -09, MB SL600 -94, MB 560SL, MB 170s, Austin Healey Sprite
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834 Posts
Discussion Starter #3
Have you checked amount of refigerant? (my 2nd same advice at short time lol). My C219 (imported from Sweden! :) ) was blowing only lukewarm from middle and kept whistle noise which changed when turning. I changed also water valve but true reason was lack of freezer fluid.
Yeah, checked and rechecked, also checked the electric circulation pump for the heating. I even flushed the system and replaced the coolant.
 

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'71 Pinto
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4,359 Posts
Definitive diagnose, have someone check for fault coders using MB Xentry/DAS (diagnostics). Reluctant to pull codes, before replacing thermostat next easiest DIY replacement to try is coolant temperature sensor, part # 0009056102. No change proceed to thermostat – your call.
 

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