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Author Topic: 12v or 24v under the dash?  (Read 1066 times)
Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« on: January 21, 2007, 07:19:36 PM »

I've got the instrument panel taken apart on my MC-5 to trouble shoot a fuel gauge problem. (The sending unit was bad) The previous owner built a new instrument panel and while they were in there, rewired most everything. You can still see the old cloth covered wire in there but the water temp and fuel gauge have been rewired. Everything I check is 12 volt. The bus is still 24 volt - at least the starter and alternator are 24v. Shouldn't those gauges be 24 volt? Did MCI step down the voltage for the instrument panel on the MC5?

Also, the fuel tank sending unit has "12V" stamped on it. The only replacements I've been able to locate are 24v units for an MC-9. I am being told that the voltage rating of the sending unit is not important as it merely references ground to give a voltage back to the gauge. Does it matter what the voltage rating of the sending unit is?

I'm glad Gumpy is back in town. I've got lots of questions for him now that he is retired.

Fred
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Fred Thomson
John E. Smith
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« Reply #1 on: January 21, 2007, 07:29:04 PM »

Fred, I know that all of the switching is 24 volt but I'm not sure about the guages -- I think they are too.

Who ever told you that about the fuel sending unit was wrong -- partially.  Yes, it gives a reference to ground, but the voltage it is designed for is what sets the range of reference.  Using a 12 volt sending unit will result in your tank always reading 1/2 full when full because the return voltage even at tank full will only be 12 volts -- half of what the guage expects to see.
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John E. Smith
gumpy
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Slightly modified 1982 MC9


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« Reply #2 on: January 22, 2007, 03:23:37 PM »


I'm glad Gumpy is back in town. I've got lots of questions for him now that he is retired.


Heeheehee.. You know how to get hold of me.  Smiley

However, if you need me to come over there, I may have to drive my backhoe and leave it there. The
city has given me till Friday to move if off my property. I left a message for the code officer's boss
today, requesting a meeting. Still waiting for a return call. Big surprise there.

I took a drive through her neighborhood. 56% of the houses on her street have at least one violation of the code. I'll be presenting my list of addresses to her boss when we meet. Then I'll check his neighborhood, and the mayor and council member's neighborhoods.

Anyone want to buy a backhoe?

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Craig Shepard
Located in Minnesquito

http://bus.gumpydog.com - "Some Assembly Required"
NewbeeMC9
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1981 MC9 8V71, HT 740




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« Reply #3 on: January 22, 2007, 04:06:36 PM »

Hope you took pictures when you went, and if you do decided to complain, make sure you use regisered mail,  Also mention first that singling you out and ignoring others is harassment.  Yes play the H card or at least ask them what that is called when someone is singled out.  that way they said it, not you

good luck

(details on the backhoe ?)

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Heeheehee.. You know how to get hold of me. Smiley

However, if you need me to come over there, I may have to drive my backhoe and leave it there. The
city has given me till Friday to move if off my property. I left a message for the code officer's boss
today, requesting a meeting. Still waiting for a return call. Big surprise there.

I took a drive through her neighborhood. 56% of the houses on her street have at least one violation of the code. I'll be presenting my list of addresses to her boss when we meet. Then I'll check his neighborhood, and the mayor and council member's neighborhoods.

Anyone want to buy a backhoe?


Quote

 more details on the backhoe?
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It's all fun and games til someone gets hurt. Wink
Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« Reply #4 on: January 22, 2007, 07:29:29 PM »

Craig,
If you can get it here, you can store it here. We already discussed its too heavy for my gooseneck so fill up your thermos with coffee and hit the road! We'll discuss rent after you get here.
Fred
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Fred Thomson
Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« Reply #5 on: January 23, 2007, 06:25:08 AM »

Upon closer inspection, the water temp and fuel gauge both have resistors on the hot side stepping the voltage from 24 down to about 14v. I bought a new MCI sending unit and it works just fine with the Stewart Warner 12v fuel gauge. (which suprised me).
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Fred Thomson
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« Reply #6 on: January 23, 2007, 08:03:37 AM »

Craig, contact the press (print and TV), too. They love a good story... David vs. Goliath, etc. Keep your head, though. You've got to impress upon everyone that you're the sane one.

And the way that you can write, you might consider blogging about it. Take pics, upload documents, etc. You've got an army of busnut brethren that can bolster your feeds/ rankings, post comments, etc.. I'm reading a book now on how blogs brought down Trent Lott, buried Dan Rather's career, and exposed plagiarizer Jayson Blair of the NYT.

Give 'em heck,
bb

p.s. Apologies to Fred for the OT stuff...
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Brian Brown
4108-216 w/ V730
Longmont, CO
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