Momentary switch testing

Skykingrob · August 24, 2009, 07:24:49 PM

Guys
I have a DPDT momentary switch on my generator that is supposed to engage the starter to start the generator. The starter no longer engages and I suspect the switch may be bad but I would like to test the switch to make sure rather than just replacing it. I know it is cheap to just replace but I am trying to make this a learning experience for me as well. So I thought I had figured it out buy using my multimeter in the conductivity mode and throwing the switch to what would be the closed position. Wrong! The meter sounds the tone when holding the leads together indicating conductivity but when I put the leads on the poles of the switch, no tone indicating conductivity. Aha, I say, I am right, a bad switch. I purchased a new switch and guess what, samething, no tone without installing it. I must be doing something wrong. What am I not understanding?

Rob
91 Prevost LeMirage XL
Missouri

Melbo · August 24, 2009, 09:20:38 PM

how many contacts are there on the switch

Are they labeled

Where do you get contact and can you post a picture

Melbo

JackConrad · August 25, 2009, 05:12:31 AM

If you push the top of the switch(rocker type) or lift the switch lever (toggle type), that should complete the connection between the center terminals and the bottom terminals (left center terminal to left lower terminal & right center teminal to right lower terminal).
When we had a problem with intermittant "starter won't work" problem with our PowerTech generator, I found a loose connection in the wiring box on the generator. Jack

Skykingrob · August 25, 2009, 07:08:04 PM

Mel
There are 3 terminals. There is a center and one on each side of the switch. It is toggle type switch.

Jack
That is exactly what I thought as well. I put one lead of the multitester on the center and one on one of the end terminals, then flipped the toggle to that side. I thought it should sound the tone indicating conductivity. Not so, which baffled me, so I went to the other side and tried it, still no joy. I have traced all the wiring, all is tight, so don't think it is a loose wire.

The only other thing I could think of is this is an Onan unit and wonder if the circuit board may have something to do with the start. Just not sure. I have looked at the manual and found nothing. This unit has "eaten" starter solenoids from the time I have owned it about every 18-24 months for unknown reasons. I keep a rebuilt starter with a new solenoid handy just so I can do a quick exchange. I thought this was the reason for the non-start so that was the first thing I replaced, but alas, no joy after replacing the newly rebuilt starter. I am out of ideas so I guess I will call out the generator tech.

Thanks for trying to help.

Rob
91 Prevost LeMirage XL
Missouri

bobofthenorth · August 25, 2009, 07:21:22 PM

Not that it matters a whole lot but for future reference, that is a SINGLE pole, double throw (SPDT) switch. I was getting hung up on the double pole momentary contact idea - this makes more sense.

Dreamscape · August 25, 2009, 08:32:24 PM

This is interesting, what model of Onan do you have?

Paul

Sean · August 25, 2009, 08:58:28 PM

Quote from: Skykingrob on August 25, 2009, 07:08:04 PM
.... I put one lead of the multitester on the center and one on one of the end terminals, then flipped the toggle to that side. I thought it should sound the tone indicating conductivity. Not so, which baffled me, so I went to the other side and tried it, still no joy.

Rob,

On most SPDT switches, whether momentary or not, when the toggle lever is moved to one side, the two terminals on the opposite side are the ones which connect. So if you are measuring between the two terminals on the same side as the lever handle, you've got the wrong ones, and they will read "open."

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

Melbo · August 25, 2009, 09:01:53 PM

Try to flip the switch each way.

There are only three combinations with only three terminals A to B -- A to C or B to C -- however there are three switch positions for each combination

The middle the right or the left.

Try each switch position with each combination of terminals (as a side note be sure to check your tester)

It is a switch and somewhere has to make some kind of contact

Let us know

Melbo

luvrbus · August 25, 2009, 09:08:49 PM

Rob sounds like you have a bad relay between the glow plugs relay and the starter switch

good luck

Dreamscape · August 26, 2009, 07:25:15 AM

I had a similar problem on our Onan DJC model when I first bought the coach in 03. I think Clifford is on to something when he said relay. I had a problem with my gen set not starting, thought it was a bad starter, had it rebuilt. Still no worky. I removed the panel box and found a bad relay, can't tell you which one though, I think there are two. I installed a new relay and the problem has disappeared, started every time since then.

That's why I was asking about your model number to compare your problem to what I had.

Paul

Sojourner · August 26, 2009, 10:13:41 AM

Quote from: luvrbus on August 25, 2009, 09:08:49 PM
Rob sounds like you have a bad relay between the glow plugs relay and the starter switch

good luck

Amen!

All ICE starter have a relay in between the switch & starter. It to transfer the cranking load to the heavier switch of the 2.

ICE mean internal combustion engine

Sojourn for Christ, Gerald

Skykingrob · August 26, 2009, 06:01:27 PM

Guys
Thanks for the info. Bob, I get the DPDT and SPDT confused, sorry, my bad. See, this proves it is a learning experience, at least for me. I will try the switch again with the new info and look for a relay. It is a 12.5K Onan, will have to look up the model number.
Thanks

Rob
91 Prevost LeMirage XL
Missouri

Dreamscape · August 26, 2009, 06:05:30 PM

Rob,

I thought mine was a 12.5 kw until I read the tag, it cleary says 12.0 kw. I know it's not a big deal, just thought you might look real close to the tag to make sure what size it is. Hope to hear from you on Model.

Paul