Generac generator

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Jan 1, 2013
My in dash generator starter switch, and the generator switch on the side of the generator will not start my generator. It will not do anything. Anyone have any answers?..  "Will"
If neither switch works and the generator doesn't even crank to start, then the problem is basic electrical. Your generator starter is 12v powered, either from the chassis battery or house (depends on the year/make/model of RV). Either it is not getting any 12v, or the starter relay in the generator itself isn't closing in response to either switch.
You know... The keyboard works a whole lot better.... When you plug it in.

If nothign, and I mean NOTHING happens. then the suspect list starts with totally dead And I mean DEAD!! batteries.

Disconnect switch (OFF or malfunction)

Bad connection

Blown fuse

Now if it was just one switch that woudl be on the list, but both of them kind, though not ruling it out COMPLETLY, makes it real, real far down the list.

Above that is a bad generator control system (The on-generator control computer) not much above both switches, but above it.

Steps to follow..

First find the big bolt with the red cap that says 12V+ beside it.. Check for voltage relative to the generator chassis. (And to the motor home chass9s) if either of those is zero, problem narrowed down to the power supply side.  From there start looking for 12vdc.
Both batteries tested good but weak.  They were plugged in to household current which should have charged them. I removed them and had them charged fully. Still nothing... I turned on one house light. It barely came on. Still nothing from the switched...
If the batteries are known to be fully charged and you only have a dim house light, you have a bad connection somewhere near the batteries.

Even a little bit of corrosion on a battery terminal, or between a wire lug and it's wire, can block electrical flow.

Disconnect any external power from the rig (unplug the electrical cord) and take off the wires going to the batteries one at a time.  Soak their ends in a solution of baking soda dissolved in water.  If there is any acid present the solution will bubble as it is neutralizing the acid. Sometimes you can have a clean terminal but have corrosion hiding where the lug attaches to the wire.

Pour some of the solution onto the battery terminals to neutralize any acid there, but don't let it get into the cells.  Use a wire brush and make sure everything is clean and tight, including where the ground wire attaches to the frame.
We are having the same problem with our Onan LP 6500 generator. It has been working, but now will only crank and not start. We have replaced the spark plugs and 10 amp (f1) fuse, cleaned the terminals. We have strong new batteries and plenty of propane. The manual recommends changing/checking the second fuse (F2), but we can't find it. I have searched the forum for this topic and can't find anything that says how to locate that fuse. Any help would be appreciated.
On a propane generator, check carefully the condition of the tube connecting the regulator to the throttle body (carburetor).  The diaphram in the regulator uses the venturi vacuum to regulate the fuel flow, and there isn't much vacuum to spare at cranking speeds.  Even a small leak can reduce the vacuum at the regulator enough to keep it from passing fuel.
Other possibilities if the generator cranks but does not start is the fuel pump relay, the low oil level safety cutout can be bad (or the oil level can be down), or the overheat protection relay can be open. The connections for the cutouts are shown on the wiring diagram and can be tested by jumping the connectors.
A couple more things.... if the LP supply was opened too fast the regulator is not feeding it...
On my gen-set there is an oil temp switch which grounds out the oil pressure is behind the oil pressure switch..
Mine is an old Generac [1994] and I spent $400 before I found out the sending unit was bad...and found a good place for parts.. in PA.

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