Original fan with maxxecu pops the fuse

[S2_avant 19930325]

Hi
How much can i go up with amp on fuse , i have maxxecu and original fan. Just when maxxecu activates it , sometimes the 40 amp fuse pops. Probably the fan draws a lot of amps just when it starts. Is there a way to build a reliable twin fuse solution ,, so it starts a bit slower for a second and then goes to max speed ? You can use a PMW modul there is one compatible with maxxecu ,

• Max load 60A (peak load such as fuel pumps)
• 50A max load for continuous loads like fan
• Protected against overload and temperature
• Wiring harness, fuses, fuse holders and main relay included!

Just wonder if there is something other out there that can be used ?

Could i just use a 70 amp relay with 60 amp fuse and fat cables ?

It is just in the begining it probably need much AMPS , when its already rotating it does not need so much AMPS .. correct ?

[Tractor Dave]

Yes, just fit a relay for the fan.

[Tractor Dave]

And, check the insulation on the fan connectors is good as they are very close together.

[S2_avant 19930325]

i have relay and 40amp fuse ,, but it pops when it starts ,, it starts at max power that why it pops

[Tractor Dave]

Strange. Was it running ok before you switched ecu? Have you checked for a short with multi meter?

[S2_avant 19930325]

I bought the fan ,, and mounted it ,, i bought the car as a prpäoject , has not driven it yet. But if its a short dont it blow the fuse everytime ? the fan has a ground wire and 12 v. The electrical is new. How do you mean check for short with multimeter ? I think best is to buy a electtical tool so i can see how much AMP it draws.

[Tractor Dave]

Have a read up here. Might help
http://www.google.co.uk/url?q=https:...COC6v5G9UypesQ

[Error404]

Factory rad fan fuse is 60A, becasue the in-rush current on that big 500w fan is huge and full power current draw ~ 40A. So you need a bigger fuse.
What not just use a relay to flip the MaxxECU GPO signal into a high-side switch which the factory relay is looking for?
Otherwise, MaxxECU PWM module will control the fan over CAN no problem - obviously some work to install it.

[S2_avant 19930325]

What not just use a relay to flip the MaxxECU GPO signal into a high-side switch which the factory relay is looking for? ... Could you explain that little more exact ? What i need little more exactly.

[Error404]

In Audi factory rad fan wiring, the rad fan switch controls the rad fan relays with a high-side switch input, i.e. the switch feeds 12v to the relay coil which closes the relay and switches power to the fan motor.
The MaxxECU outputs are low-side switches, meaning they switch to ground. So in order to control the factory rad fans relays, you must convert you MaxxECU switch output to provide a 12v to the relay coils.

This is easy, you just need another 4 pin relay - take 12v to the relay 30 terminal and 86 terminal. Connect relay 87 terminal to the factory rad fan relay coils. The connect your MaxxECU GPO to relay terminal 85. When you switch the your GPO on, this closes the flipper relay which feeds 12v to the factory rad fan relay, switching on the fan.

[S2_avant 19930325]

Aha .. ok ,, that is the way i have it now installed. But i have a 40 amp relay with a 40 amp fuse. So i need to buy i 70 amp relay and have 60 amp fuse.
Correct ?

[Error404]

Yes

[S2_avant 19930325]

Yes

Problem solved Error 404 ,, ,,, i mesured to how much it draws. The fan draws 38 amps on full speed , but on exacty the moment it start for 0,1 sek it shows beteween 80-115 amps. It is normal , and the fuse is made to hold for that for that short time.

[Error404]

Yes the fan motor have a big in-rush current when they start up, but it is only for an instant as you have found, so the fuse should hold
But it is a good idea to control the fan through the ECU so you can give the engine a shot of air on idle as the fan kicks in to avoid the revs dropping

[S2_avant 19930325]

I set that in the maxxecu , does not drop at all now.