yeah, the second wire doesn't do anything.
If you wire it up to positive, nothing happens.

I think we wired one backwards originally, and it just sparked, no smoke, but don't remember for sure.

Mine is wired the same way on the bench.If it was wrong it wouldn't have ran.Swap out the fan shourd and send it back. Electric motor bad.

If you cross the main power and ground wires things get ugly. It will short with enough current to make the teeth on jumper cables glow orange. That happens within 10 seconds of connecting the two wires. Leave it like that and smoke will follow in a minute or so. No doubt it's hard on the capacitors inside the motor.


BTW... Temic and Brose make the fans for Mercedes. The motors I have were made for them by Siemens.

Siemens makes about 90% of the factory fan motors if not more.If you have a siemens fan motor you have one of the best.

here's what the instruction sheet said that came with the fan.

this fan assembly is an electronic device which has to be installed according to a special test procedure, please follow the steps below. we will not accept responsibility for any damage.
the fan assembly has to be mounted into the vehicle before testing, because the control unit requires a PWM signal, please do not use "power supply" test, otherwise the IC card will burn out.

there's more, but it's just stuff not relevant to this discussion.

basically it's telling me that the fan should not be used with normal system voltage. this is a replacement fan for a C class mercedes though.
i tried to talk to one of the techs at the dealership about it but unless i'm willing to pay the 155.00 per hour they won't let me talk to anyone. this dealership is hard to deal with. i was hoping maybe Feets could ask one of the techs how much voltage the fan is supposed to see under normal circumstances. no point in burning up another fan if i can't find out.
of course my other question is do i need to limit the voltage to the trigger wire, or the voltage to the main positive lead, or both???
any help would be greatly appreciated.

I wonder if that's some sort of initialization thing. I haven't had any issues with mine. Andy and Kirk haven't had any problems with theirs. All of ours came out of wrecked cars.
I'll see if there are any techs working tonight. Most of them have gone home by now.

well, like I said, toss a ballast resistor inline with the trigger wire.
Won't put more than 8 volts or so to it.
Don't know how you would get it to fast speed then.

I found a shop foreman before I left work. This is what we've got...

There are two types of fans on these cars.



The older fan is on top. It was replaced by the new style shown on the bottom.
The fans are indeed controlled by pulse width modulation. Essentially, the computer sends pulses to the controller kinda like a strobe light. If it flashes slow, the fan runs on low speed. If it flashes fast, the fan runs on high speed.
The computer sends that signal to the little metal box on the fan. That box reads the signals and turns on the low speed or high speed on the fan. When that box fails, the fan won't work.
The fan motor is seldom harmed when that happens. The smoke leaks out of the control box, not the motor. Four large wires come out of that box. You can bypass the box and wire straight to the leads. The fan will blow on the speed you've set.
The new style fans have the speed control built into the motor. When they get a constant 12 volt signal they default to high speed. That is a fail-safe that prevents the engine from overheating.

Apparently, the aftermarket fans are made cheaply and don't have the fail-safe logic built in. Should you have one that fails, bypass the metal box and wire directly. The fan will run just fine.

Since the majority of fans I have played with were the new style, I had no idea there would be a problem.

Apparently, all the smoke leaked out of your fan. You can contact the company and see if they will warranty the fan. Since they have that statement in the paperwork, they must know it's an issue. If they refuse to warranty the fan or if you simply don't want to mess with all that again, bypass the box and wire up the fan. I'm not sure which leads will provide which speed. I will play with my donor and see what I can find out.

Do you have a part number on the newer style fan setup?

Do you really want to pay over $500 for a fan? The factory fan isn't cheap. Aftermarket pieces will drop in and work like the original equipment. If they have the control box, I'd simply bypass it and wire to the leads on the other side of the box. If the aftermarket guys tooled up to build the old style fan, I doubt seriously they retooled to produce an entirely new part when theirs will work.
You can try asking at a regular parts store for an aftermarket 2006 Mercedes C230 fan and see if it is the new style.

To answer your question directly, no. I do not have the number handy. I can get it at work tomorrow if you like.

i suppose wiring the fan directly would be possible, but it would take a 50 amp relay i suspect.
so perhaps the ballast resistor on the trigger wire is the answer???
it seems like it would basically achieve the same thing, right. or am i missing something?
the fan i have has that big metal box on it like the one you pictured.

actually no, the ballast resistor idea won't work based on feets explination.

To send a pulsed signal you would have to wire in one of the dash voltage regulatros.
But that is a 3 pronged item.

It would send a 12 volt on off signal.

I would bet the relay is still built into the motor if there are 4 wires coming out of the motor to the box. So you are still good with your old wiring.

The problem is I live in Florida and it's 100 degrees everyday! If i was able to find a powerful enough fan for cheap i would be more than satisfied, I just don't know what to tell from pushing pulling reverse amps cfm etc.

You have this big ass intercooled i dont even know and it seems you have enough information about the fans in the junkyards that this would be a best bet scenario.

If bypassing the control box works, you'll want to use a relay.
Bosch relay number 0 332 002 150 (Echlin AR298) is a 75 amp relay.



Note the measurements are metric.

You can run this in conjunction with a thermostatic switch to control the fan.

If wiring the fan directly works like my shop foreman stated, you should be able to use high and low speeds. One switch for high, one for low.

One relay for each speed.

If your temp switch throws a ground to trigger a fan, it can be used to ground the relay and spin up the fan. You will have a harder hit on the electrical system than with the easy start the factory provided. It should still be under the limits of this relay. The spike would dissipate quickly. It would probably be visible in dimming headlights if your system isn't ultra stable.

i'm going to give it a try. just one more thought on this for now. i have a feeling that since the fan control unit was designed for PWM, the motor itelf never really recieves full system voltage. the pwm happens so fast that the fan will run smoothly at a designed rpm. with full voltage that thing might suck the radiator right out of the car.
and just an observation, the fan has little metal balance weights on it.
thanks for the help and the offer. i'll let you know how it works out.