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Help! Can someone point me to the wiring diagram for the radiator fan circuit from the SAMs through the relay and to the fan? I cannot find it in the factory manual nor on the internet. Problem is car's fan wont work so I thought the best place to begin troubleshooting was to check the control/power circuits to the fan. I found on alldata/owners manual the fan relay location and power side fuse. Upon checking the relay i see voltage at the coil side which is strange as a/c if off and car engine is cool. Also, i found no voltage from the power side fuse to the common terminal. i checked the fuse 28 and found it to be good. I believe the way this circuit works is the the SAMs unit switches the coil voltage which then trips the relay and applies power the fan. Does anyone else have more info or experience with this circuit. Curious why is the wiring schematic is hard to find?

Note I want understand the control circuit and validate its operation before i go yanking out the fan. Any help on this path is appreciated.

mdm
 

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Mercedes (and smart) are very secretive about most things on their cars. the factory manual only exists on their computer website and is quite expensive unless you have a need for it say like a dealership. Most of their circuits are powered all the time and they control the ground side, which is the opposite of US cars.

the fan circuit should run the fan when it gets above a specific temp outside and the AC is turned to the full on position I usually also turn on the recirculate switch too. the fan should run continuously. I have seen problems with the fan mounts breaking, bushings seizing. and wire breaks on the fans.To replace the fan, the whole front of the car has to be removed to get to the fan assembly, including the radiator and condensor, it sounds worse than it is. but still a good 10 hour job. When my fan mount broke on my '09, I added a second fan on the front of the radiator that pushed air through. Fan was around $70 and a lot less time even with figuring out some sort of mount. I used the current fan wiring and I ran the car for 2 1/2 years with no problems until it had other issues not related to the fan. From the outside , you couldn't tell any changes were made. Just saved a ton of money and time.
 

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The smart service info is worthless for this. The component location index shows the radiator fan relay but the wiring diagram for the power and ground distribution shows the radiator fan powered directly from the SAM on a RED/BLU wire. The BRN wire on the fan connector is ground. Nowhere do the wiring diagrams show a radiator fan control relay. Not in the cooling system, the engine management or the climate control system. Once again, the German Engineering left hand is not talking to the right hand.

If you have 4 wires to the radiator fan relay the heavier gauge wires are the switched power to the fan motor and the smaller gauge are the control wires. Pretty much all modern vehicles have the control relays ground controlled so the relay coil will always be powered with the key on and the ground to the relay coil switched on and off to operate the relay.

Item M4/2 on the attached diagram is the radiator fan motor.

The simple way to test this is with a capable scan tool that will activate the radiator fan. By operating the fan from the scan tool you can verify whether the relay is working when commanded. The poor man's way is with the key on-engine off switch the a/c on and off to see if the fan relay operates at which time you can test for power in and out of the relay. I am assuming the fan will be switched whether the engine is off or on. I have never tried it. You may have to test with the engine running. If you have power out of the relay to the fan motor the next step is to test at the fan itself. In fact, that might be the first step. If power is there and the fan is not running then it is NFG. One can tap on the fan motor with it powered and see if it starts to run.
 

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Mercedes (and smart) are very secretive about most things on their cars. the factory manual only exists on their computer website and is quite expensive unless you have a need for it say like a dealership. Most of their circuits are powered all the time and they control the ground side, which is the opposite of US cars.

the fan circuit should run the fan when it gets above a specific temp outside and the AC is turned to the full on position I usually also turn on the recirculate switch too. the fan should run continuously. I have seen problems with the fan mounts breaking, bushings seizing. and wire breaks on the fans.To replace the fan, the whole front of the car has to be removed to get to the fan assembly, including the radiator and condensor, it sounds worse than it is. but still a good 10 hour job. When my fan mount broke on my '09, I added a second fan on the front of the radiator that pushed air through. Fan was around $70 and a lot less time even with figuring out some sort of mount. I used the current fan wiring and I ran the car for 2 1/2 years with no problems until it had other issues not related to the fan. From the outside , you couldn't tell any changes were made. Just saved a ton of money and time.
my fan has apparently quit and rather than tearing everything apart to replace the original puller fan i would like to go the route you have gone with a pusher fan in front.

could you please tell me what size/type/brand/model/etc fan you used so that i can order it and have it on hand when i tear the front end off.

thank you

Bill
 

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my fan has apparently quit and rather than tearing everything apart to replace the original puller fan i would like to go the route you have gone with a pusher fan in front.

could you please tell me what size/type/brand/model/etc fan you used so that i can order it and have it on hand when i tear the front end off.

thank you

Bill
Bill this post, is over 4 years old. I don’t think Jimwv57 is around anymore.
 

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thanks... i've gleaned enough info from other sources to see that a Hayden 3690 or a Flex-a-lite 394 are recommended.

quandary now is, the hayden is 1250cfm, 11.5amps and the flex is 1530cfm, 9 amps... seems like a nobrainer, maybe

Bill
 

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Go with the lower amp one as if you pull too much it will trigger a over draw code in the Sam unit.
Mine was done with a pusher game and the one the previous owner used had started to seize and tripped the code(which shut the fan down completely)
Once I replaced it and my buddy cleared the code it was good to go.
Btw if it doesn’t work after you install it don’t fret just get the code pulled and cleared.
 

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Go with the lower amp one as if you pull too much it will trigger a over draw code in the Sam unit.
Mine was done with a pusher game and the one the previous owner used had started to seize and tripped the code(which shut the fan down completely)
Once I replaced it and my buddy cleared the code it was good to go.
Btw if it doesn’t work after you install it don’t fret just get the code pulled and cleared.
Thank you. I was trying to find out what the cfm and amperage of the OEM fan is, but no luck. Didn’t want to blow too much air through as I’m sure there is too much of a good thing (and don’t want to suck Fiats in)

My thought too; and if necessary, I can use a relay to reduce the load but hopefully that won’t be necessary.

the flex-a-lite is twice as expensive as the hayden but seems to be the appropriate choice
Bill
 

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I’ll put it this way paying a bit more for the higher cfm fan is better then paying for a possible engine failure if it isn’t cooled properly and overheats.
 

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I’ll put it this way paying a bit more for the higher cfm fan is better then paying for a possible engine failure if it isn’t cooled properly and overheats.
I’ll put it this way paying a bit more for the higher cfm fan is better then paying for a possible engine failure if it isn’t cooled properly and overheats.
i agree....:) i have a 2008 with an engine that has gone bad that i've kept as a parts car, but there is no way on God's green earth that i was going to take all that stuff apart to be able to swap out an OEM style fan; it was great to have run across the forum post about just installing a pusher... easy peasy... (except nothing is truly easy on an older vehicle)

while the front is off, and if there will be enough clearance to the fan, i might install the Blue Ox from the 2008 to this car.

AND, if it's appropriate, Happy Father's Day to you

Bill
 

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There should be.
I still have the pic from where I swapped the fan on mine if you want me to upload it.
I don’t have kids but my father is still with me.
 

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There should be.
I still have the pic from where I swapped the fan on mine if you want me to upload it.
I don’t have kids but my father is still with me.
Thank you again

I’m not sure what bracketry I will use to mount the fan; maybe one on each side to control lateral movement and 2 on the bottom to bear the weight.

you can PM the pictures or you can post them (might be of use to others in the same dilemma

Bill
 

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When I did mine I used two at the top and same at the bottom.
I got the metal I used from my local ace hardware store.
I’ll snap a pic of how I got them done later today as I have to pull the front panels off to work on my passenger side headlight.
 

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When I did mine I used two at the top and same at the bottom.
I got the metal I used from my local ace hardware store.
I’ll snap a pic of how I got them done later today as I have to pull the front panels off to work on my passenger side headlight.
while i've got your attention... have you found a better/easier way to put the rocker panels back on? it has always been the hardest part of the job... i have ordered the newer black clips and hope that i will be able to slip them into the retainers on the panels and then just push it onto the studs rather than sliding the panel.

Bill
 

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I’ve just been pulling the front top clip that catches on the front panels out and away just enough to get to the screws on the bottom that hold the panels(I use a power tool to work with the screws so it takes less time)
I’ll pull the front panels off today as I gotta start working on fixing my passenger side headlight housing so I can snap pics of everything.
 

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I’ve just been pulling the front top clip that catches on the front panels out and away just enough to get to the screws on the bottom that hold the panels(I use a power tool to work with the screws so it takes less time)
I’ll pull the front panels off today as I gotta start working on fixing my passenger side headlight housing so I can snap pics of everything.
I put a cheap 14" fan from eBay. I haven't changed stock temperature sensor yet but under a scanner I can read the temperature. That fan has worked flawlessly and I put a heat-sensor-coupler under the coolant tank. It is controlled by a relay and has worked perfectly. I intend though to remove the coupler under the coolant tank reconnect it as stock and use a different probe that goes between the radiator fins or actually in the hose. Those are usually temperature adjustable Right now I am having problems after an accident Different thread
66867
 

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When I did mine I used two at the top and same at the bottom.
I got the metal I used from my local ace hardware store.
I’ll snap a pic of how I got them done later today as I have to pull the front panels off to work on my passenger side headlight.
I mounted my fan to the condenser with those plastic (not nylon) zip ties, pad & spring. ONLY (the zip ties strip or half-strip when you put them on) On the inner side of the condenser, after trimming and getting the tie to hold with the spring, I dropped epoxy glue on the end with the condenser off the vehicle. Did a neat job and recent inspection shows the 4 ties are holding perfectly with the epoxy
 

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I intend to use the original fan wiring to control the fan operation as the fan has to not only run when the a/c is running but also to separately control engine temperature; all I presume is done by multiple sensors.

i don’t like the idea of supporting the fan by/through the condenser/radiator. I will securely mount the fan with some kind of bracketry let to be determined

Bill
 

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Here’s pics of how I did the mounting of mine(will get better pics when I can get to remove the panels and it’s not going to storm)
I used a metal strip from ace hardware and cut it to reach where I wanted the fan to be and drilled holes in the top ones and used the included hardware for the fan to hold it to the top ones and just wedged it in place at the bottom.
I don’t like running stuff or supporting the weight of the fan on the condenser.
Ran the fan directly off the car’s wires and it works great and kicks on when needed when the a/c is off and on when the compressor is on when the a/c is on.
It’s worked via the Sam unit directly(no relay except the one in the sam unit as my car only has three relays)
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66870
 

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the fan came today and i installed it (pictures below), but unfortunately i probably won't be able to in install the Blue Ox without some serious modification to its mounting brackets as the fan's
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shroud appears to sit out too far. AND it is really LOUD, but i reckon it will cool VERY well
 
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