Aux fans run parameters?
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
Aux fans run parameters?
Hi all,
Under what conditions do the two auxilary fans start and stop?
Should they operate with A/C on or is it purely coolant temp dependant?
Thanks all
Under what conditions do the two auxilary fans start and stop?
Should they operate with A/C on or is it purely coolant temp dependant?
Thanks all
MBWorld Fanatic!
Joined: Mar 2005
Posts: 2,418
Likes: 194
From: America
1999 C43 AMG, 2005 E55 Wagon
It's dependent upon 2 things:
Coolant temp and refrigerant pressure. If the pressure is too low, they will never run. If the coolant temp is too low they will never run.
Coolant temp and refrigerant pressure. If the pressure is too low, they will never run. If the coolant temp is too low they will never run.
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
Coolant temp got to a bit over 100°c, but that was sitting still for a fair while, and it never seems to go higher that that. When moving it sits just above 80°c.
It seems to hold coolant temp very stable, and has been even more so since the new water pump got installed.
It seems to hold coolant temp very stable, and has been even more so since the new water pump got installed.
MBWorld Fanatic!
Joined: Mar 2005
Posts: 2,418
Likes: 194
From: America
1999 C43 AMG, 2005 E55 Wagon
those are typical temps for them. my cooling system and AC are all in tip top shape and it never breaks 100C, and when driving it hardly breaks 80C even with the 55 motor (which makes it run slightly hotter than my 43 motor)
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
So the fans work, wired them to a battery and theyre fine.
Is there a way to test them via the A/C controller like on the dual zone systems where you hold both AUTO buttons?
If i hold the AUTO button, after a few seconds the screen displays only the fan speed, and all blocks in that are blank except the middle one.
Is there a way to test them via the A/C controller like on the dual zone systems where you hold both AUTO buttons?
If i hold the AUTO button, after a few seconds the screen displays only the fan speed, and all blocks in that are blank except the middle one.
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
Prefer to diagnose the car first, via SDS,
go to "Air Condition" section, it may needs to operate the controller,,
or you have a bad coolant sensor..!
-;ZAYED;-
go to "Air Condition" section, it may needs to operate the controller,,
or you have a bad coolant sensor..!
-;ZAYED;-
Trending Topics
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
Coolant sensor is fine, it is new about 4 months ago. The coolant doesnt get high enough for the fans.
The fans should be coming on with A/C high pressure but theyre not.
The fans should be coming on with A/C high pressure but theyre not.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
ECU reads the temp. of the coolant sensor, it's one of important thing to operate the fan via controller,
fan could interrupt if there is not enough gas in the air condition system, have to check that,,
also, have to see if everything in "Air Condition" circle are fine, through SDS..
-;ZAYED;-
fan could interrupt if there is not enough gas in the air condition system, have to check that,,
also, have to see if everything in "Air Condition" circle are fine, through SDS..
-;ZAYED;-
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
A/C gas level is correct, its been checked.
Coolant temps are fine and all that is operating correctly.
When viewing pressure via the A/C controller it gets up as high as 29°1 on the display, which seems very high.
I would assume A/C pressure switch is working because it displays a reading that rises and falls with the compressor operation, and if i hold revs about 2,000rpm to get the fan spinning faster the A/C head pressure comes down well.
How can i operate the fans via the A/C controller?
Coolant temps are fine and all that is operating correctly.
When viewing pressure via the A/C controller it gets up as high as 29°1 on the display, which seems very high.
I would assume A/C pressure switch is working because it displays a reading that rises and falls with the compressor operation, and if i hold revs about 2,000rpm to get the fan spinning faster the A/C head pressure comes down well.
How can i operate the fans via the A/C controller?
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
I don't think A/C controller can be operated manually, it takes all operating ranges through pressure sensors,
"drier gas & temp. sensors & evap. sensor"
-;ZAYED;-
"drier gas & temp. sensors & evap. sensor"
-;ZAYED;-
MBWorld Fanatic!
Joined: Mar 2010
Posts: 5,889
Likes: 323
From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
I'm attaching the fan operating specs if this helps... As Zayed says I would also check the A/C diagnostics and the codes in the ECU.
Also added the HEVAC codes and identification details
Also added the HEVAC codes and identification details
Last edited by DRBC43AMG; Apr 28, 2017 at 05:31 AM. Reason: Added second .pdf file
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
Checked all that, had no codes there in either current or past.
That fan .pdf seems to be for a much older model, my relays are quite different to those and have no fuses on them.
That fan .pdf seems to be for a much older model, my relays are quite different to those and have no fuses on them.
MBWorld Fanatic!
Joined: Mar 2010
Posts: 5,889
Likes: 323
From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
Did you measure the voltage of the controller..?,
if i'm not mistaken;
try to measure pin #1 & #4, it should indicate (13.6>>13,8), that's the main power source to the controller,
#5 for the fans speed, with fans not working it will gives (0V),,
with Engine start & A/C on, #2 & #3 should to indicates more than (11.xxxV)...!
-;ZAYED;-
if i'm not mistaken;
try to measure pin #1 & #4, it should indicate (13.6>>13,8), that's the main power source to the controller,
#5 for the fans speed, with fans not working it will gives (0V),,
with Engine start & A/C on, #2 & #3 should to indicates more than (11.xxxV)...!
-;ZAYED;-
Thread Starter
Senior Member
Joined: Feb 2017
Posts: 392
Likes: 9
From: Australia
W202 C43 1999
You wont believe what the fault was here...
Someone had removed the fuse at some point, and never put it back in. Buggered if i know why they took it out, but there is one in there now and my fans work fine.
Someone had removed the fuse at some point, and never put it back in. Buggered if i know why they took it out, but there is one in there now and my fans work fine.
MBWorld Fanatic!
Joined: Mar 2010
Posts: 5,889
Likes: 323
From: Land of mountains, cheese, chocolate and watches
12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
Good to hear you found the problem. A fuse is a simple and cheap solution 
Newbie
Joined: Aug 2021
Posts: 5
Likes: 0
C220
Regards
