Oil pressure warning light - start up

[docc]

That one wire grounds the light to illuminate it, right? Using just a screwdriver grounding that wire, still no oil light with the key on?

Is there continuity from the switch end of the blue wire to the bulb end of the blue wire?

[4corsa]

Checking that in a minute Docc, meanwhile, here is that circuit in the wiring diagram. #12 being the oil pressure switch:

[4corsa]

That one wire grounds the light to illuminate it, right? Using just a screwdriver grounding that wire, still no oil light with the key on?
Is there continuity from the switch end of the blue wire to the bulb end of the blue wire?

Ok, so when I connect a grounded wire to the disconnected oil pressure switch wire, I get the bulb to light with key on engine off!

[docc]

7 minutes ago, 4corsa said:

1 hour ago, docc said:

That one wire grounds the light to illuminate it, right? Using just a screwdriver grounding that wire, still no oil light with the key on?
Is there continuity from the switch end of the blue wire to the bulb end of the blue wire?

Ok, so when I connect a grounded wire to the disconnected oil pressure switch wire, I get the bulb to light with key on engine off!

Progress! Make sure the connection to the switch is clean and treated.

Also, there should be continuity from the switch connection to the engine case with the engine off.

[gstallons]

1 hour ago, 4corsa said:

Also, I'm assuming the connector to the oil pressure switch is supposed to have just one wire.

Yes . you should get 12v at this wire with KOEO . If so , ground this lead and your light should be on . If it is , the oil pressure switch is bad .

[4corsa]

The pin male connector of the oil pressure switch is not grounded neither with key on or off. There must not be continuity to the engine case. I connected my test light clip to the pin and touched the probe to the positive battery terminal with key on and off - no light.

[docc]

1 hour ago, gstallons said:

Yes . you should get 12v at this wire with KOEO . If so , ground this lead and your light should be on . If it is , the oil pressure switch is bad .

+1

1 hour ago, 4corsa said:

The pin male connector of the oil pressure switch is not grounded neither with key on or off. There must not be continuity to the engine case. I connected my test light clip to the pin and touched the probe to the positive battery terminal with key on and off - no light.

Bad switch.

 

[docc]

https://www.mgcycle.com/index.php?main_page=advanced_search_result&search_in_description=1&keyword=GU17768750

$10.90US !

For another $1.84, I added this sealing boot over the connector:

https://www.mgcycle.com/index.php?main_page=product_info&cPath=37_209&products_id=315

[4corsa]

Many thanks Docc and gstallons! I'll let you know if the be switch solves the problem. Seems like it must be it.

[Lucky Phil]

37 minutes ago, 4corsa said:

The pin male connector of the oil pressure switch is not grounded neither with key on or off. There must not be continuity to the engine case. I connected my test light clip to the pin and touched the probe to the positive battery terminal with key on and off - no light.

Wow 3 pages of pulling the bike apart and I had the answer in the second post. As I said then, if the wire hasn't fallen off the switch and the light comes on if you ground the switch wire and turn the ignition on then its the switch.  

Ciao

[4corsa]

You are correct Lucky Phil and thank you. I should have done that first, but got side tracked with a number of the items that were related to the starter issue, mainly getting to the ignition and taking that apart.
But thank you again for your help - much appreciated!

[Lucky Phil]

1 hour ago, 4corsa said:

You are correct Lucky Phil and thank you. I should have done that first, but got side tracked with a number of the items that were related to the starter issue, mainly getting to the ignition and taking that apart.
But thank you again for your help - much appreciated!

Yes when I caught up on the thread I thought that might have happened. Would never have happened to me of course, I'm to much of a "one tracker" as my wife keeps reminding me:) No side roads and one catastrophe at a time, then move onto the next. That's me.

Ciao 

[po18guy]

You know, in an incoherent Guzzi electrical engineer sort of way (now there's a contradiction in terms!), grounding via the oil pressure switch makes sense. If there is oil pressure, no need for the starter. Thus, if the light is out, either the sender or the bulb is DOA.

Note: mid 60s Ducati 250s had a mystery toggle switch on the taillight bracket. No one ever figured out what it did. Oddly, a guy on the Kawi EX500 forum advised me:

"I owned one of those Dianas once upon a time. The brake light circuit ran off the ground side of the primary ignition coil which was down in the flywheel magneto. The ignition coil was grounded by the brake light switch during normal operation. When you applied the rear brake, the switch opened and the ignition coil ground then had to go through the filament, lighting up the bulb. If the bulb burnt out, every time you hit the rear brake, the engine would quit so they put the switch there to act as an emergency ground. Clever or stupid? Take your pick."

That designer must have taught Guzzi a few tricks.

[docc]

On the V11, I can't see how the oil pressure switch would affect starting.  If that starting issue proves changed on 4corsa's V11, I expect it is due to servicing the Ignition Switch.

If it doesn't prove changed, we shall surely dive in again!         

[4corsa]

I agree, and always considered the two separate issues, unless related to cleaning the ground cables at the battery, which proved not the case for the oil pressure warning light.  It was just convenient to work on both at the same time, with fairing removed, etc.