Faulty TPS? - Switchable Auto - Ohm values included

[Rtaylor2208]

Does anyone have details on to how to test the TPS for a switchable auto? The auto has a 6 pin switch opposed to the manual 3 pin one.

I am struggling to identify which pins are which for testing continuity.

[Brianmoooore]

Don't have the connections to hand, but it should be easy to sort with a resistance meter.
Three of the pins are the same as the ordinary TPS , and the other three are a pot. There is no electrical connection between the two.
At rest, three of the pins should have a measurable resistance between all of them. This is the pot.
Two of these pins will have a fixed resistance between them, whatever the position of the throttle, so these are the two ends of the pot, and the third pin is the wiper/signal out. The pin which has a very low resistance to the wiper when the throttle is closed is the earth end of the pot., and the other pin is for the DC fixed voltage.
The other three pins are the same as an ordinary TPS, so two should be shorted together with the throttle closed. As soon as the throttle moves all three pins should be open circuit from each other, but at mid to full throttle the third pin and one of the first two pins should be shorted together.

[Rtaylor2208]

Thanks Brian, as soon as my new mutlitmeter leads arrive i'll give this a shot. My exisitng ones are just the regular probe ones which are bloody fidly to keep connected to get a reading.

Once \ If I get it tested successfully I'll document it for the Wiki.

[Rtaylor2208]

So an update on this. The pins for the pot are 1,2 and 3. The pins for the TPS are 4,5,6.

Testing the resistance between 4 and 5 gives no resistance till almost full throttle where it becomes an open circuit.

Testing between pins 4 and 6 has a resistance at throttle closed but as soon as the throttle moves it goes to short circuit.

The switch clicks as soon as the throttle is moved. So does this sound like it just needs a clean out? I don't have any contact cleaner is there something else I can use as an alternative?

[Rtaylor2208]

Bump

[Brianmoooore]

WD40 should be OK. It's not so much cleaning switch contacts that's required, but flushing out oil that has found its way in.
Are you sure you've written your results correctly? The switch appears to be working, but some of your open and short circuits seem to be the wrong way around.

[Rtaylor2208]

Brian I'll retest tonight and take a note of the values that might help explain better as I may be getting the terminolgy wrong.

[Rtaylor2208]

So retested and the values I get are:

With pins 4 + 5 connected I get a reading of 1 ohm when the throttle is closed. It stays at this value until at almost full throttle open when I get a reading of approx 30 ohms.

With pins 4 + 6 connected I get a reading of 3.2 ohms when the throttle is closed. As soon as the throttle is opened I get a reading of 1 ohm.

With pins 5 and 6 connected I get a reading of 1 ohm regardless of throttle position.

Does this sound correct?

[Brianmoooore]

It makes sense if your "1 ohm" is actually the over range indication on your meter, and means infinity, or at least higher than the meter can measure. Very different from a genuine 1 ohm, which will be displayed as 1.0 ohms.
The 3.2 ohm reading is the closed contact reading of a 'proper' microswitch, and should ideally be zero, but will be good enough to tell the ECU what it needs to know.
The 30 ohm reading is that from a simple leaf spring touching a cam, and again should ideally be zero, although such a crude switch is often quite resistive.
Contact cleaner would probably improve the 30 ohms, but is unlikely to get right inside the microswitch to help there.

[Rtaylor2208]

Brian i would love to say that I understood all of the above but could you put that in lay terms at all?

Does that mean the switch is then faulty or at least giving an incorrect reading?

The display on the multimeter is reading "1." Regardless of the terminals attached to anything at all.

I also have it set to the 200 ohms range on the dial.

[Brianmoooore]

"1" displayed on your meter doesn't mean 1 ohm. If you are on the 200 ohms range, then it means "greater than 200 ohms".
The resistance readings you get means that the switches aren't perfect (no switch is), but they are good enough.

[Rtaylor2208]

Thank you Brian, Much easier to understand. I can now start putting all the inlet side back together.