Bosch PWM Idle Valve Polarity

[Bainzy]

Does anyone know the wiring that would ensure correct polarity for the Bosch PWM Idle Valve 0 280 140 516?

I've got one ready to wire up but there's no markings on the unit, so I have no idea as to which pin is which, or which wire goes to 12v and which goes to the ECU

[dontz125]

It doesn't really matter - you can set the polarity in the settings. If "0% duty" has your idle racing, you can either swap the wires or change the settings to 100% = closed.

[elaw]

Dontz,

You're confusing "polarity" with "polarity"!

The OP's question relates to which wire connects to which terminal on the idle valve. My answer is I don't think it matters, but I'm not 100% sure of that.

What you're talking about is the polarity of the MS output signal, as in does it go low or high when the valve should be turned on. That's more of a software-vs.-hardware question.

[dontz125]

Hi, Eric.

Read my post again - if having +12v to the left pin and MS on the right gives a too-high idle at 0% duty, he can either swap the wire polarity or swap the duty polarity.

Nyaah!

[elaw]

Doh... I just realized where the confusion is... I think!

For a 3-wire idle valve, you're absolutely right - swapping the outer pins reverses the valve's function. However I think the OP's is a 2-wire valve, in which case electrical polarity should not matter. Unless the valve has a diode inside, then it does.

[dontz125]

According to the manual, some 2-wire valves open against a spring; some close against it. The direction of force is a function of coil winding and current flow, so it will matter - to the extent that if it's wrong, it'll have to be swapped.

[Bainzy]

Thanks guys, yes to clarify it's the two wire valve.

Would it damage the valve if wired wrong? I don't mind trying it out and switching afterwards as long as I know wiring it backwards won't break it.

[Bainzy]

Anyone?

[BenGTT]

On this valve, pin 1 should be 12V and pin 2 the PWM control. Almost sure (99%)

[john.p.clegg]

Double check if you can before connecting,don't know about the Bosch,but some of the Fords have an in-built diode and small polarity markings on the case...wrong connection will ruin them...do you have a multi-meter?
John

[Bainzy]

I do have a multimeter John, how would I use it?

BenGTT - that's great, thanks. Looking at this picture, which pin is 1 and which pin is 2?

[jsmcortina]

I'm almost certain that it doesn't matter on those valves. I had one in my hand yesterday but gave it back to the owner.

James

[john.p.clegg]

On the left hand unit you can just see 1 and 2 in the grey plastic base..
John
P.S.
I'll dig out a valve and test it before giving you "duff" info..

[Bainzy]

Had the valve wired up but can't seem to get it to do anything. Using a 12v feed and the MS3X idle wire in both ways of connecting, each time I can get it to make the valve click when powering on the Megasquirt, but that's it.

I'm using the following settings: http://www.msextra.com/forums/viewtopic ... 71&t=11001

The only way I can get it to click is use inverted on the PWM warmup settings. When I run an idle valve test, nothing happens whatever values or settings I use, it stays open.

Given that the MS3X produces the output, and I didn't build it, does this sound like the problem could only be a duff idle valve?

[Marek]

Dear Bainzy,

With the unit wired up, but not fitted to the car, you should be able to see the little circular cylinder/barrel that is the orifice controlling the amount of air.

If it is a Bosch 0 208 140 516 run at 100Hz, then the latest Tunserstudio view of test mode should let you verify visually that the valve is closed at about 40% duty and wide open at 80% duty. Numbers below 40% duty will start to open the valve again.

kind regards
Marek

[Bainzy]

Thanks Marek, that's exactly what I tried and couldn't see it move. So I wonder if the idle valve is defective?

[elaw]

It's easy to test... hook a couple of wires to it, and connect 12 volts to the wires. If you're using a high-current source like a battery, I'd recommend putting a 5A fuse in series for safety.

When powered the valve should go fully open, and of course it should close when you remove power.

[Bainzy]

Eric, I believe the valve is open when unpowered (as a failsafe), so I'm not sure that test would work.

[elaw]

That really isn't true, although it can appear to be!

If you look inside the valve, there's a rotating mechanism with a "shutter" that when it moves can obstruct the outlet to varying degrees - that's how it regulates idle speed.

When the valve is deenergized, the shutter is a little past the fully-closed position, so there's a slot exposed where air can get through. That's the opening you see when you look at the valve in its inert state.

If you connected a power supply to the valve and started slowly increasing the current supplied to it (equivalent to varying the PWM signal coming from the Megasquirt) you'd see that shutter move in a direction that initially *closes* the valve. That, as far as the Megasquirt is concerned, is the "zero" position of the valve, even though the current is not zero.

If you then increase the current (or PWM value) more, the shutter moves further and a slot will begin to open on its other side. Increasing the current enough will create an opening much larger than the one you see when the valve is unpowered.

Or to put it another way, "zero" power opens the valve some, "full" power opens it all the way, and the closed position is somewhere between the two. Does that make sense?

If you hold the valve and watch the mechanism while applying power to it, all will become clear...

[jsmcortina]

Just connect the valve to a car battery and feel/see if it moves. It nothing happens then bin the valve and get another one.

James