Modern Vespa

2008 MP3 500
My cooling fan will only run if I bypass the factory wiring, even though I have 12 volts on factory connector.
Replaced connector, no change.

Thanks for any ideas

Here's a video of my diagnostics.
I did test ground/earth resistance after I made the video and it was only 00.5

https://youtu.be/mZ_8HtKB-Uk

I take it the gauge works, but the fan doesn't? Try swapping over the wires to the two sensors. They're in one unit, one sensor feeds just the gauge, the other feeds the ECU and via that, the fan.

So, which bit of the factory wiring did you bypass? The whole fan relay or just the 'ground' coil feed from the ECU?

I bypassed from battery to connector on fan assembly; fan run.

I have 12 volts on the connector that connects to the fan assembly connector I tested to. Take a look at the video, only 2 minutes or so.

What volts are there on the connector when the fan is connected though? Your meter is high impedance, so the volts could be via a high resistance. Have you tried swapping out the fan relay? Those contacts can get HR with arcing etc, as the fan is a very inductive load.

Will figure out which relay is for the fan and swap it out to test and then test volt at fan connector while fan should be running while the fan is connected.

JimC

Thank you very much for the advice, it was the relay. Fan is working again as it should.

If you are in the Washington DC area and need a scooter to ride you can borrow any of mine and I'll buy you a pint at one of our many fine local breweries.

Wayne B

Glad it worked out.

I doubt I'll get to DC again anytime soon, so have an extra beer yourself.