uS cutout with electric fan

[Steven]

having a great day getting things working but i had been having having a problem with the electric fan causing interference. i had disconnected it while i concentrated on the important things, like starting and running.

as soon as the electric fan starts is causes the uS to cut out. it starts up again but then cuts out. by listening to the fuel pump its about a 2s off and 2s on cycle.

fingers crossed this will be a capacitor or diode installation simple fix but its beyond my understanding.

Help...

Steven

[racingmini_mtl]

Are you connecting the fan directly to the uS or are you using a relay? The fan will draw a lot more current than the uS can handle so you need a relay.

Jean

[Steven]

Jean
I tried new ground direct to battery then ground and live direct to battery, I think it's just interference. Tomorrow I was going to try running it from a separate battery. Also just made me think the ve sensor is not shielded on the engine side of the firewall. I don't really want to pull that wire out so is it possible to fix the fan?

Steven

P.s. The truck seems to be running ok...

[racingmini_mtl]

I guess I misunderstood. I thought you were controlling the fan from your uS but you seem to be saying that when the fan turns on (from its own switch and not controlled from the uS), the uS cuts out. Is that correct?

Also, you say you tried with the fan directly connected to the battery but you don't say if that changed anything. Make sure you have a good ground on your uS and that your wiring is a per the manual.

Jean

[Steven]

Jean
sometimes when i write things down its clear to me but i dont think about how it sounds to others...

the fan is completely separate from the microsquirt it sown relay and temp switch on the engine. but when its running it does reach out and touch something.

because of the earlier cutting out problem i 'bullet proofed' the ground situation. by the way the cutting out was the vr sensor wired backwards, revs very well now.

i'm going to pick up some shielded cable today and ask some advise at work on how to stop interference from the fan motor.

Regards Steven

p.s. i let you know how it goes.

[MWPau]

Where is the +ve supply for the fan coming from?
Fans draw a LOT of current on startup. If its sharing some of the same supply cable as the uS im guessing thats the issue.
The startup current of the fan might be pulling the uS supply too low.

[Steven]

MWP
i have run wires directly from the battery and the problem is exactly the same. now that i have the intercooler in front of the radiator i need the fan more than ever.

i'm going to try rerouting the wire under the engine away from the fan.
i'm trying to get some shielded wire, see if that works.
i have asked some questions about stopping the noise from the fan (i havent got a clue about this one, is it a capacitor issue).

i'll post the solution when i find it.

[Steven]

got it... i changed out the wires to the VR sensor with a shielded cable and it worked no more cutting out, fixed! a work colleague also suggested putting a capacitor across the motor but as its working right now and i have other fish to fry i'm going to leave it for now.

[Steven]

Put the truck away last year and pulled it out again and the fan interference is back. When the fan starts the fuel pump and o2 relay goes crazy, plus sounds like the other relays also. Last year I fitted a shielded cable from the vr sensor (grounded at the sensor) and it seemed to work. This year it's returned and I'm stumped. The only thing I have found out is that it does not do it if it's run from a different battery. If the fan is direct to the truck battery also no problem. Fan has its own relay. Tried ferit eon the sensor and fan wires, no change.... I will attach logs tomorrow but I'm not sure there needed here.

[Matt Cramer]

Where exactly are the MS and the fan getting power and ground?

[Steven]

Matt
The power is coming from the main battery to starter lead, there is a tap off point half way ( it came of a larger Chevrolet truck ) the ground is connected to a robust ribbon that connects the chassis, body and engine together.

I had this suspicion myself so I:-
connected the fan directly to the battery and it made no difference, I.e. Still cutting out.
I connected the fan to different battery it worked perfectly fine, no cutting out
I wrapped the motor in tin foil no difference

The fan motor is very close to the ve sensor but the ve sensor wiring is away from everything that could cause problems.

I also just gave the ve sensor wiring shield a better ground path to the bracket I.e. Screw and star washer, no change.

I'm about to buy another fan, because I'm stuck...!

Also I measured the voltage at the uS fuse when the fan was on and it was over 12v

[Matt Cramer]

It could well be some sort of arcing issue with the fan motor.

[Steven]

Matt
New fan fixed the issue. Thanks for the advice.

Regards Steven