Where is the relay for the A/C condenser fan on 2007 3500

Phantompilot

New member
3500 diesel with Itasca RV conversion. Electric A/C condenser fan runs all the time. Local mechanic says it is a relay "welded closed." I need to find that relay. Since it is a RV conversion the fuse/relay locations are not standard About to remove the drivers seat to find if it is there, but thought maybe someone has seen this problem and could help.
Thx in advance.
 

Phantompilot

New member
Not part of the RV but Winnebago put relays in a lot of different places. Took me a month to find the one that controls the running lights; it is under the passenger seat. The fuse box on the side of the drivers seat only has about 10 fuses and is not the same as in the users handbook that came with the van.
 

Cheyenne

UK 2004 T1N 313CDi
I seem to recall Dennis (LinDen Engineering) saying the relays are mounted on the fan shroud on an NCV3 so that would be the best place to start lookibg.

Have you read the service manuals for the 2007's on DIY Sprinter, link below?

Keith.
 

lindenengineering

Well-known member
Well as I have posted, NORMALLY its found in the fixed section of the lower section of the fixed fan shroud, passenger's side on left hooker . Remove the grill to expose it!
BUT beware !!!!
Take squint through the grill and sees if there are two condenser fans or NONE!
If there are just big round gaping holes where fans might have been, then because its a 3500 the MAIN engine cooling fan will be electrically coupled.
It serves as both engine and condenser fan cooling.
So NO relay on these model derivatives


With these particular derivatives, if you leave the engine idling and the A/C operational the compressor head pressure will signal the engine cooling fan to mysteriously start coupling like a Boeing at take off when pressures exceed 350 psi .
Then it will mysteriously shut down once pressures are reduced to about 200 psi or so
Just like a Landrover !!!
I suppose emulation is the finest form of flattery!! :)
Dennis
 

Phantompilot

New member
Thx for the help. This 3500 has one fan visible on the drivers side. Easy to tell when running. I would not have looked on the shroud for the relay but shall this morning. Troubleshooting in the afternoon in Texas now limited by temperatures. 104 F+ through Monday. Hopefully the service docs will provide more info also.
 

lindenengineering

Well-known member
Thx for the help. This 3500 has one fan visible on the drivers side. Easy to tell when running. I would not have looked on the shroud for the relay but shall this morning. Troubleshooting in the afternoon in Texas now limited by temperatures. 104 F+ through Monday. Hopefully the service docs will provide more info also.
Yes look for the two #4 battery cables going to it inside a recess.
Yes it was 101 here in Denver yesterday and I did an emergency turbo replacement with a hot engine on a T1N.
Hot topixs:( and this 70 odd year old showed them, my yung uns how to work in Iraqi like temperatures.
Took me 2,5 hours to complete--bloody hot finger scorching manifolding.
Dennis
 

Phantompilot

New member
Grill off. Fan and shroud exposed but no relay visible. A MB parts guy said it might be inside the cooling fan itself.
Seems this is the year model that MB and Dodge parted company, so the VIN doesn't appear on one or the other in different computers.
Anyway, still looking. Any suggestions to fix this would be appreciated. I guess I will take out the passenger seat next to see if Winnebago stuck something weird in there, although I can't imagine why they would mess with the A/C system.
One last thing. Since this condenser has only one electric fan is it possible it has the main engine fan electrically coupled also?
 

lindenengineering

Well-known member
Grill off. Fan and shroud exposed but no relay visible. A MB parts guy said it might be inside the cooling fan itself.
Seems this is the year model that MB and Dodge parted company, so the VIN doesn't appear on one or the other in different computers.
Anyway, still looking. Any suggestions to fix this would be appreciated. I guess I will take out the passenger seat next to see if Winnebago stuck something weird in there, although I can't imagine why they would mess with the A/C system.
One last thing. Since this condenser has only one electric fan is it possible it has the main engine fan electrically coupled also?
Yes!
Dennis
 

220629

Well-known member
Is your engine a V6 or in line 5 cylinder? A 2007 RV conversion could be a T1N truck.

If it is a T1N the relay is under the seat.

vic
 

Phantompilot

New member
Was able to disconnect the power to the fan by pulling the plug on the lower cooling fan shroud passenger side. Thank you Dennis. Now wondering if that relay is downstream from there? Also if this is a defective pressure head sensor that is reading above 350 PSI? Would have the same effect as a shorted relay and make the fan run continuously?
 

autostaretx

Erratic Member
Seems this is the year model that MB and Dodge parted company, so the VIN doesn't appear on one or the other in different computers.
Enter your VIN to one (or all) of these sites ... you'll get your datacard:

https://www.vindecoderz.com/EN/Mercedes-Benz <-- datacards
https://www.datamb.com/ <-- datacards
https://www.mbdecoder.com/ <-- datacards (more up-to-date?)

Up near the top, there will also be your VID ... it will look like a VIN, but the first 9 digits will differ.
Whenever you hit a "you're not in our system", try that VID.

Then try entering your VIN to http://mbepc.net/f/vin/ for direct access to MB's electronic parts catalog.

VIN/VID example (mine)
VIN: WDRPD1443558212..
VID: WDR903671158212.. .. yes, my body type is 903.

--dick
 

Phantompilot

New member
Well as I have posted, NORMALLY its found in the fixed section of the lower section of the fixed fan shroud, passenger's side on left hooker . Remove the grill to expose it!
BUT beware !!!!
Take squint through the grill and sees if there are two condenser fans or NONE!
If there are just big round gaping holes where fans might have been, then because its a 3500 the MAIN engine cooling fan will be electrically coupled.
It serves as both engine and condenser fan cooling.
So NO relay on these model derivatives


With these particular derivatives, if you leave the engine idling and the A/C operational the compressor head pressure will signal the engine cooling fan to mysteriously start coupling like a Boeing at take off when pressures exceed 350 psi .
Then it will mysteriously shut down once pressures are reduced to about 200 psi or so
Just like a Landrover !!!
I suppose emulation is the finest form of flattery!! :)
Dennis
Sorry to bother you again, but I am getting no help here. I can unplug the connector for the fan on the lower side of the shroud, passenger side. This stops the fan. The wiring is 2 large current cables and 2 smaller wires. Is the relay built into this connector?
Dealers and local mechanics aren't too interested because they are busy as hell and don't like the Sprinter/RV connection.
If I knew where the relay was I could change it, but I have been over the service manual and can't locate where the data is.
Thanks in advance.
 

piggy

New member
Did you ever find out where the ac relay is and did you fix the problem? I am having the same problem
 

autostaretx

Erratic Member
What year is your Sprinter?

Your MB fuse allocation booklet covers where MB placed relays (if it's the relay for their fan)

--dick
 

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