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Discussion Starter #1
Hey guys. Just picked up my new to me 99 cl500 yesterday after having it shipped from LA.

I new that the heater did not work but unfortunately i did not realize that it was going to be 9 degrees here in KY when i picked it up!

SO i ran the code check thru the climate unit. came up with these

code 231
code 418
code 417
code 416

i have been searching the forums since this afternoon and cannot find what these valuse mean for the new climate control (NON PUSH BUTTON PRE 96 type)

I have a duo valve lined up for tomorrow to replace before i head back to atlanta but i want to make sure thats the right part before i spend the money

any help guys. And if this has already been listed i apologize i really searched and found nothing!!!

thanks again
 

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At home i have link to site that has codes for the newer type of control module, but iam currently at work so cant help you, if you dont find it till then i will post the link here once i get home....
 

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Discussion Starter #3
thanks so much that would be great. Its just so damn cold here!!!

hoping its not a heater core!!!

thanks again and i look forward to seeing it!
 

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No its wont be heater core, it would be leaking somewhere otherwise (unless its plugged up :) i bet you $20 its duo valves stuck in closed possition....(to fix that ..ranges from tap by hammer to refurbishment...or replacement $$$)
 

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Discussion Starter #5
i hope its not the core

I have tried the hammer tap from another post here. no avail although i did not go at it with full force.

and of course the codes are driving me nuts but hopefully you can help me out with that

any other symptoms of the duo valve that i should look for? it does make a little motor like noise but i dont know what to look for besides that

thanks!
 

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well the intake big hose into the duovalve will be hot and so should be the little small hoses coming out of it (if it is working properly when heater is on) but if they are somewhat cooler then valves are closed shut....
 

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thank you so much! not sure how i missed that post but i guess i did. SO the only question now is the ect. i have not searched yet but do you happen to know where it is located? if not no big deal i will find it.

I was hoping that was all it was!! again thanks so much you have been such a great help!!!
 

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thank you so much! not sure how i missed that post but i guess i did. SO the only question now is the ect. i have not searched yet but do you happen to know where it is located? if not no big deal i will find it.

I was hoping that was all it was!! again thanks so much you have been such a great help!!!
Dont take that recirculation pump and ECT sensor(its a coolant temp sensor) error too seriously, but those duo valve codes sound about right,
try to erase them and see which ones come back just to be sure...
I had whole bunch of errors and after clearing them i only go two to come back....
 

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Check out my article covering the rear duovalve. Same issues, and it will give you an idea of how they function.

V12 Uber Alles, Rear AC System and Duovalve Diagnosis Rebuild in a W140 Mercedes Benz

For the front, refer to the attached file and text below....

Coolant
Drain.

2 electrical connectors
Disconnect.

5 hose straps
Release and pull off hoses.

2 rubber mounts for heating system delivery unit (arrows)
Press off and remove heating system delivery unit

Install
In the reverse sequence, top up coolant and bleed heating system by turning both temperature selectors to the red segments and running the engine at alternating speeds.

Function check
 

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