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U280 fuze for boost switch

March 05, 2016, 09:43:47 am

Hi, hard for me to see fuze issues.. is there one for the boost switch.

Light was working.. it was working.. now nothing.. no click sound

Another concern is.. why this would happen?

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Re: U280 fuze for boost switch

Reply #1 – March 05, 2016, 10:41:57 am

Don't know about a fuze but do know that the little lite burns out quickly. May just be a burned out bulb.

Roland

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Re: U280 fuze for boost switch

Reply #2 – March 05, 2016, 12:16:00 pm

John,

Looking at my wiring diagram, I don't see any fuse.  The BOOST switch is powered directly off the battery side of the IGN solenoid (under the lift-up dash cover).  Try working the switch while someone stands at the rear driver side wheel well.  They should hear the solenoid closing.

If you want to try a new bulb, I think it is a #2721, either GE or Sylvania LL 

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Re: U280 fuze for boost switch

Reply #3 – March 05, 2016, 12:40:47 pm

I don't know if a '94 is the same but the input power feed into the boost switch on my '91 actually has two feeds to it.  One from the house battery and the other from the chassis battery.  Each feed passes through a diode before being joined into one wire.  For those not familiar, a diode acts like a check valve for electrical current.  In a worse case scenario of a dead battery, the switch will operate regardless of which battery goes dead.  The diode prevents both battery banks from being connected to each other when the boost switch is off.  The diodes were soldered inline to the wires and covered with heat shrink tubing.  I would suspect the power feed into the switch is the most likely issue.

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Re: U280 fuze for boost switch

Reply #4 – March 05, 2016, 03:25:06 pm

Ok I hear a thunk in the front dash.. where is it? Engine compartment..

I have a voltage meter for both the engine-cigarette lighter an another directly to the coach battery.

When I turn the boost switch on.. shouldn't the engine battery voltage go up a bit?

House at 13.2
Engine at 12.1
Before turning on boost

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Re: U280 fuze for boost switch

Reply #5 – March 05, 2016, 08:57:44 pm

I think for your year, the boost relay is located on a 12 volt panel that is usually mounted on the basement wall between the tanks and storage - drivers side of coach.  There should be a white fiberglass cover over it held on with a couple of thumb screws.  If boost relay is working it should get a little warm after its been on for a while.  Boost relay looks just like the ignition relay that is under the dash.
At the bottom of this post is good photo of the boost relay with a label on it: Boost switch
Other possible locations are behind the drivers wheel (as shown in photo) or under the bed.
And, yes, typically the engine voltage will rise a little when the boost switch is activated (with engine off).

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Re: U280 fuze for boost switch

Reply #6 – March 11, 2017, 10:45:12 am

Ok.. what boost solenoid should I buy? Volt meter on it nada... thanks twig for showing me where it is..

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