Murphy Switch

Topic: Murphy Switch (Read 724 times) previous topic - next topic

Murphy Switch

March 20, 2023, 09:24:07 pm

Found a Murphy interrupter switch in the dash.
Think I understand well enough what it does, just wondering what the "proper" use of such a device would be.

Thanks

Re: Murphy Switch

Reply #1 – March 20, 2023, 09:26:39 pm

Mystery Switches inside dash

How to check fault codes?

Switches behind drivers dash

What are these switches for?

secret? switches inside dash

Re: Murphy Switch

Reply #2 – March 20, 2023, 09:59:18 pm

Thank you. Good info there.
Really looking for info on a Murphy Magnetic Switch Model TD-781.
Seems that it kills power to the fuel pump when activated. Not sure why our coach would need such.
For some reason the picture wouldn't attach.

Re: Murphy Switch

Reply #3 – March 20, 2023, 10:11:05 pm

Quote from: Phranko – March 20, 2023, 09:59:18 pm

Thank you. Good info there.
Really looking for info on a Murphy Magnetic Switch Model TD-781.

Ah, I had assumed an autocorrect from Murphy to Mystery, as those are the only switches in the dash I've ever seen mentioned/asked about.

Re: Murphy Switch

Reply #4 – March 20, 2023, 10:40:12 pm

I have one on my '81 FTX on the generator. I have been familiar with the name since I was a kid.

Lincoln B2B NA.

Re: Murphy Switch

Reply #5 – March 20, 2023, 10:43:56 pm

Chuck that's the only thing I came up with....

Re: Murphy Switch

Reply #6 – March 20, 2023, 10:45:19 pm

Quote from: craneman – March 20, 2023, 10:40:12 pm

I have one on my '81 FTX on the generator. I have been familiar with the name since I was a kid.

Lincoln B2B NA.

Thanks Craneman..... for what purpose on our coach?

Re: Murphy Switch

Reply #7 – March 21, 2023, 12:47:43 am

The newer coaches use electronic sending units to the ecm do the same thing the Murphy switch does mechanically. The one on my '81 has mechanical contacts. Nothing to do with the switches under our dashes.

Re: Murphy Switch

Reply #8 – March 21, 2023, 08:37:45 am

Quote from: Phranko – March 20, 2023, 10:45:19 pm

Thanks Craneman..... for what purpose on our coach?

Quote from: craneman – March 21, 2023, 12:47:43 am

The newer coaches use electronic sending units to the ecm do the same thing the Murphy switch does mechanically.

OK, but WHAT DOES THE MURPHY SWITCH DO! Nobody has answered that question...

Why is the switch installed on Frank's coach?

Re: Murphy Switch

Reply #9 – March 21, 2023, 08:45:23 am

Quote from: Chuck & Jeannie – March 21, 2023, 08:37:45 am

OK, but WHAT DOES THE MURPHY SWITCH DO! Nobody has answered that question...

Why is the switch installed on Frank's coach?

"Engine protection system Murphy Switch
This article explains the engine protection system used in several older Classic II, Classic III, SA-250, and SAE-400 engine driven welding generators that used a Murphy switch."

[HIGHLY offensive comment removed - Michelle]

Lincoln B2B NA

Re: Murphy Switch

Reply #10 – March 21, 2023, 08:51:10 am

Quote from: Old Toolmaker – March 21, 2023, 08:45:23 am

"Engine protection system Murphy Switch"

Yes, I read that link, but it's too complumcated fer me. I need a "6-year-old mental level 'splanation" for why its on a Foretravel. Humor me. Does every older model coach have one? If not, why not?

Re: Murphy Switch

Reply #11 – March 21, 2023, 09:15:34 am

Quote from: Chuck & Jeannie – March 21, 2023, 08:51:10 am

Yes, I read that link, but it's too complumcated fer me. I need a "6-year old mental level 'splanation" for why its on a Foretravel. Humor me. Does every coach have one? If not, why not?

Who knows what the previous owner did, but it's an aftermarket switch to shut down the engine after a loss of oil pressure or a fan belt breaks. The "Murphy Interrupter Switch" might allow the operator to start the engine without building oil pressure first.

The only specialized knowledge required for the reading is the Deutz engine protection: Deutz makes air cooled diesel engines, fan belt breaks, engine overheats.

Re: Murphy Switch

Reply #12 – March 21, 2023, 09:40:24 am

It may have grounds from the oil pressure and temp lights , to shut off the fuel solenoid?

Re: Murphy Switch

Reply #13 – March 21, 2023, 09:47:54 am

OK, so a aftermarket switch, probably added by a previous owner. Not found on every coach, I would assume. Possibly installed to provide added layer of protection for engine. Although I would assume the ECU on the electronic engines (like Frank's '99 U320) already had those features built in.

Re: Murphy Switch

Reply #14 – March 21, 2023, 09:50:27 am

Quote from: Chuck & Jeannie – March 21, 2023, 09:47:54 am

OK, so a aftermarket switch, probably added by a previous owner. Not found on every coach, I would assume. Possibly installed to provide added layer of protection for engine. Although I would assume the ECU on the electronic engines already had that feature built in.

So:
Frank & Connie Williams
1999 U320 '36
Build: 5466
MC: 18335

Is this still a DD or something more modern. Either way the fuel injection's disable until there's oil pressure. Am I correct?

Re: Murphy Switch

Reply #15 – March 21, 2023, 10:22:15 am

You could simply ground the fuel pump solinoid through the oil pressure switch. Save a lot of wires

Re: Murphy Switch

Reply #16 – March 21, 2023, 10:40:54 am

All the input is appreciated and since it's not a stock item so I'm going to guess the PO probably installed it to help him sleep better. We all do the same thing just with different parts and pieces.
It made no sense to me to have it that's why I asked the group.
Maybe the PO was a welder as was mentioned, pretty sure the answer will remain lost.
Not a DD we now run a M11.

Re: Murphy Switch

Reply #17 – March 21, 2023, 10:47:23 am

Quote from: Old Toolmaker – March 21, 2023, 09:50:27 am

So:
Frank & Connie Williams
1999 U320 '36
Build: 5466
MC: 18335
Is this still a DD or something more modern. Either way the fuel injection's disable until there's oil pressure. Am I correct?

All electronic engines have several sensors for coolant level, oil pressure, temperature. The sensors are connected to the ECU and when triggered, shut the engine down. Ours goes to half power for 30 seconds and then shuts down. Some coaches may have an override button on the dash. Only to be used to move the coach and only good for a short time. If the main coolant tank is low in the morning, it won't start.

Some mechanical engines have sensors for a fuel solenoid shutoff.

Our "old" DD is still in production and sold all over the world by Mercedes/Detroit. The DDEC ECU has always been the most reliable ECU made.

Pierce

Re: Murphy Switch

Reply #18 – March 21, 2023, 12:55:43 pm

I think the PO had lots of problems with the coach so he installed the Murphy switch to keep " Murphy " from causing any more unforeseen problems.

Re: Murphy Switch

Reply #19 – March 21, 2023, 01:10:38 pm

As the article states Murphy is a brand name,commonly used in the oilfield on gas compressors and generators that are
unmanned and run for weeks at a time,try and determine what it does and call it by that function,calling it a Murphy switch is like
calling it a Honda or a Ford switch.

Re: Murphy Switch

Reply #20 – March 21, 2023, 02:44:42 pm

Quote from: rbark – March 21, 2023, 12:55:43 pm

I think the PO had lots of problems with the coach so he installed the Murphy switch to keep " Murphy " from causing any more unforeseen problems.

It seems to be working so I'll not touch it

Quote from: John44 – March 21, 2023, 01:10:38 pm

As the article states Murphy is a brand name,commonly used in the oilfield on gas compressors and generators that are
unmanned and run for weeks at a time,try and determine what it does and call it by that function,calling it a Murphy switch is like
calling it a Honda or a Ford switch.

I was unable to get the picture to load but "Murphy" is the name brand on the little box under the dash.
Murphy Magnetic Switch Model TD-781.

Re: Murphy Switch

Reply #21 – March 21, 2023, 08:38:45 pm

Quote from: Phranko – March 21, 2023, 02:44:42 pm

It seems to be working so I'll not touch it
I was unable to get the picture to load but "Murphy" is the name brand on the little box under the dash.
Murphy Magnetic Switch Model TD-781.

Trying to figure out why the previous owner did something is a fun exercise, simple reason being the most likely. In this case, the PO was probably concerned a sudden loss of oil pressure. That being said, it's something I'd keep an eye out for but not worry: Your engine ecm probably takes care of that for you already. So if your oil pressure gauge goes to zero, but the engine keeps running the engine may still have oil pressure.

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