Fuse for Heat Exchanger Pump

[winged2]

Can someone please tell me where the fuse is for the water pump on a 2012 S4? I upgraded to the cwp150 and need to upsize the fuse. There is a lot of misinformation on the internet. Thank you

[Fresh.S4]

apparently its a fuse panel by the ecu.

[SwankPeRFection]

It is the fuse panel in the ECU box. It’s on the driver side under the cowl. You’ll need to take the windshield washer fluid snorkel out and the top of the box for the ECU off. It’s the same fuse that also runs the VVT solenoids. 10AMP fuse (red). It’s either 6 or 8 in that box… I always forget. Post a picture and I can point it out.

[winged2]

Thank you. I’ll post up a pic.

[winged2]

I assume it’s the 6th one down as it’s the only 10amp fuse there. Thank you

[sepheroth86]

I think that when using the CWA150 that larger wiring with a relay is supposed to be used.

[winged2]

Never heard of that. On Merc’s website all it says is needed is the fuse change. I hope that 10amp was the right fuse.

[SwankPeRFection]

I assume it’s the 6th one down as it’s the only 10amp fuse there. Thank you

Should be it, as I do believe it’s the only one in there. Just be aware that if something happens with the fuse or the wiring on that circuit, you will have two problem. Your pump will obviously not work and the dead giveaway is extremely hot aluminum lines running down from the front of the supercharger (both sides will be extremely hot) and your engine will literally have no torque as you’re limping along because the cam phasing won’t work anymore since the VVT solenoids are on that same circuit.

If you EVER have codes for both VVT solenoids not working ALWAYS check this one fuse, don’t chase ghosts with other stuff until you’ve ruled out this one fuse.

[Smac770]

"the water pump on a 2012 S4". Which water pump?
The V188 supercharger coolant pump? This runs off the fuse 7, which powers many things on the engine.
Or the V51 afterrun engine coolant pump, if equipped? This runs off a relay.
Or the V50 HVAC heat exchanger coolant pump? This runs off a fuse on the driver's end of the dash.
The main engine coolant pump is not electrical.

I'll assume you mean the V188 since fuse 7 is the 10A fuse you're referencing in the remainder of the dialog. Fuse 1 is towards the fender. The wiring from the fuse to the splice point is 1.5mm², or ~16awg. From the splice point to the V188 is 1mm², or ~17awg. The other large consumer on that fuse is the V51, but it's unlikely the V188 and V51 are run at the same time. The other devices on that fuse 7 in the CCBA config are the motor mounts, the VVT solenoids, and the N422 hvac heat exchanger coolant cutoff solenoid.

Current capacity of a 17awg cable will depend on run length and insulation rating, but it won't help if you don't have a current draw specification for the attached device. Specs seem to imply "Current consumption: 15A max". But how much of an increase over the stock draw is that? If you slap a 15A in there, the wiring is probably fine, but is the capacity sufficient for the pump and other devices. If you slap a 20A in there, you're probably pushing the limit of what you should load onto that wiring. But will the high current draw be sustained or just in bursts? Is the pump driven steady state of PWM. Etc.

[winged2]

Well I am thoroughly confused now lol. Good information tho thank you. I just want to go fast. 🫣 Also I have a merc racing divorced set up, doubt that makes much difference in regards to what you guys are talking about. Thank you for the help and information. Btw I did email Jose at merc to ask about the wiring. I’m waiting to see what he says.

[SwankPeRFection]

That’s the fuse in the ECU box man. Mine blew when the CWA100-3 pump I had malfunctioned internally and overloaded the circuit. It’s the only red one in that box and yeah, it’s both engine mounts (which won’t affect shit), the VVT solenoids (which most definitely will make the engine feel like you just lost compression on like half of your cylinders) lol. It’s drivable, but you WILL know something is wrong with the powerband.

[sepheroth86]

Never heard of that. On Merc’s website all it says is needed is the fuse change. I hope that 10amp was the right fuse.

Are you doing a CWA100 or CWA150?

The factory CWA50 draws 5 to 7 amps.

The CWA100 draws 8.5 amps.

The CWA150 draws 15 amps.

Potential for electrical meltdown of the factory wiring is significantly higher since you will now be drawing 3x the factory amperage.

[bguild]

Does the supercharger pump also use a relay or just that one #7 fuse? I am troubleshooting a non functioning pump and wondering if there is any decent way to test the pump via ODIS without disassembling the drivers front and pulling the plug.

[Smac770]

Does the supercharger pump also use a relay or just that one #7 fuse? I am troubleshooting a non functioning pump and wondering if there is any decent way to test the pump via ODIS without disassembling the drivers front and pulling the plug.

from post #9:
"The V188 supercharger coolant pump? This runs off the fuse 7,"
vs
"Or the V51 afterrun engine coolant pump, if equipped? This runs off a relay."

So going to guess it's a direct run from fuse 7 to the pump. But that's also for a B8.0 CCBA. It's a different fuse for B8.5 CGXC or CTUB. There, it's fuse 16.

It's a communications controlled pump, the ECM doesn't control it by controlling 12v or ground connectivity. It has permanent connections to fuse and to chassis ground. So yeah, step 1, unplug it and confirm 12v from pin 1 to pin 3, assuming the output test is not causing any activity and the fuse is confirmed not blown.

Wow, it's not even the same pin, or the same plug, on the ECM for the control line for B8.0 (T94/24) vs B8.5 (T60/2).