condenser fans coming on low speed at idle now after 55 swap
Thread Starter
Junior Member
Joined: Sep 2014
Posts: 61
Likes: 0
99 c43 amg
condenser fans coming on low speed at idle now after 55 swap
Just curious if anyone with a 55 swap or a 43 still ever noticed the condenser fans coming on at idle or when the engine is a little warm...and the AC IS OFF. I never noticed them coming on..its not bad obviously but just never noticed them coming on before without the ac. And i also noticed it running slightly warmer than the 43.
Super Member
Joined: Jan 2013
Posts: 636
Likes: 29
From: MN, USA
C43 5.4, ML320CDI, Fords
Nope, mine runs the same temp as always, 8O to 85 celsius. The only time my aux fans come on is when Im using the ac in slow traffic on real hot days.
I do have a new condenser which probably helps airflow vs a 17 year old half plugged one.
I do have a new condenser which probably helps airflow vs a 17 year old half plugged one.
Thread Starter
Junior Member
Joined: Sep 2014
Posts: 61
Likes: 0
99 c43 amg
yea mine runs about the same temp as well. new radiator, water pump, and thermostat. just noticed the other night when I got home from driving around. car was already warmed up and I parked outside and left running to run inside and when I came back it was around 85-90 not near over heating at all and then I heard the condenser fans come on at a low speed. just never noticed them coming on with out the ac before. I first noticed actually after I did the swap and my car was running in the shop with the sds hooked up they came on low. I know its not a bad thing. glad they come on. just never noticed them before. but other than that car runs good with new engine. oil level light started acting up after and hour or so. oil level good and sds say oil level was in check but light was still on. so I just coded it out for now. will fix later. but oil level is fine and ive been driving hard for two days now so I thing if there was an oil issue I would of had a problem by now.
MBWorld Fanatic!
Joined: Mar 2005
Posts: 2,418
Likes: 194
From: America
1999 C43 AMG, 2005 E55 Wagon
This has happened with my car.
The function of the aux fans is tied to if the AC system is CHARGED, not if it is ENGAGED.
My ac was out on my 94 C280 for 3 years, blown evaporator. Replaced it myself and the fansstarted working at higher temps, whether the AC was on or not. Same symptoms with my C43. Cracked the condenser in my crash, replaced it during the summer, noticed same situation as my C280.
The function of the aux fans is tied to if the AC system is CHARGED, not if it is ENGAGED.
My ac was out on my 94 C280 for 3 years, blown evaporator. Replaced it myself and the fansstarted working at higher temps, whether the AC was on or not. Same symptoms with my C43. Cracked the condenser in my crash, replaced it during the summer, noticed same situation as my C280.
Thread Starter
Junior Member
Joined: Sep 2014
Posts: 61
Likes: 0
99 c43 amg
This has happened with my car.
The function of the aux fans is tied to if the AC system is CHARGED, not if it is ENGAGED.
My ac was out on my 94 C280 for 3 years, blown evaporator. Replaced it myself and the fansstarted working at higher temps, whether the AC was on or not. Same symptoms with my C43. Cracked the condenser in my crash, replaced it during the summer, noticed same situation as my C280.
The function of the aux fans is tied to if the AC system is CHARGED, not if it is ENGAGED.
My ac was out on my 94 C280 for 3 years, blown evaporator. Replaced it myself and the fansstarted working at higher temps, whether the AC was on or not. Same symptoms with my C43. Cracked the condenser in my crash, replaced it during the summer, noticed same situation as my C280.
MBWorld Fanatic!
Joined: Mar 2005
Posts: 2,418
Likes: 194
From: America
1999 C43 AMG, 2005 E55 Wagon
Yes, I understand. I'm telling you this is normal behavior. You either didn't notice it with your 4.3 motor or perhaps something was unplugged before you did the swap but is now fixed 
Super Member
Joined: Jan 2013
Posts: 636
Likes: 29
From: MN, USA
C43 5.4, ML320CDI, Fords
The aux fans can come on for two reasons.
1. The high side pressure in the AC is above a certain threshold. This obvious would not happen if the system was not charged or not operating however.
2. The engine coolant temperature is above a certain threshold. This is not dependent of anything with the AC system.
Trending Topics
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
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
Thread Starter
Junior Member
Joined: Sep 2014
Posts: 61
Likes: 0
99 c43 amg
Yeah im sure its fine. Driving the temp is right above the 80 mark and idling around 90. Just nervous with the new install i guess. I was worried getting the 55 and opening it up to find sludge...scored cylinder walls etc but happily to say that wasn't the case. But did pull out a spent jiffy lube oil filter. All looked good tho. And ran a VMI on the engine from the donor car to see some history.
MBWorld Fanatic!
Joined: Aug 2006
Posts: 7,053
Likes: 398
From: A.D., U.A.E
2000 (W202 C200) & 2000 (W202 C55)
Summer is soo soon here, temp. reaches 50c..
,
is there a good idea to let those fans operate at 80 or 85 without switch-on the A/C..?
as i remember there is a controller for those fans under the driver fender, isn't..??
can we do something to it, to let those fans operate sooner..???
ZAYED,,
, is there a good idea to let those fans operate at 80 or 85 without switch-on the A/C..?
as i remember there is a controller for those fans under the driver fender, isn't..??
can we do something to it, to let those fans operate sooner..???
ZAYED,,
Last edited by cm60k; Feb 23, 2015 at 03:23 PM.
MBWorld Fanatic!
Joined: Jan 2007
Posts: 1,152
Likes: 29
From: Sydney, Australia
190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
I added an additional variable fan controller to get the fans to come on earlier. I left the the factory system in place as a backup (still wired in) but setup the new system to leave the aux fans running at the minimum speed with engine running (I've removed the mechanical fan due to bigger radiator) and a temp sensor on the radiator outlet to ramp up the fan speed as needed that can hold engine temp at 100C on even the hottest days with the car stationary. By leaving the factory system as well as the additional fan controller the fans can still be activated by A/C temp if needed.
The one cheap mod that I can suggest is removing the aux fans and sealing the fan assembly against the A/C condenser as a lot of air was escaping at the bottom near the P/S cooler. I discovered this while setting up the aux fan controller and wondering why I had so much hot air being blown in my face while sitting in front of the car. Some thick foam or rubber glues to the back of the fan is all that's needed. Only really needed for hot climates though.
The one cheap mod that I can suggest is removing the aux fans and sealing the fan assembly against the A/C condenser as a lot of air was escaping at the bottom near the P/S cooler. I discovered this while setting up the aux fan controller and wondering why I had so much hot air being blown in my face while sitting in front of the car. Some thick foam or rubber glues to the back of the fan is all that's needed. Only really needed for hot climates though.
