Thursday, June 1, 2023


What to do about a surging RV generator

gary-736Dear Gary,
I recently purchased a toy hauler with a generator with only 27 hours on the meter. At first the governor appeared to be sticking, due to what I believe was bad fuel (varnished). I sprayed the carburetor with a cleaner and it ran fine for awhile. The idle still surges with no load applied, and if I put a heavy load on it, it seems to get better. The butterfly plate at the front of the carburetor, when pushed down manually, makes it run smooth. Any ideas? —Mike C.

Dear Mike,
With only 27 hours on the generator, I’m surprised you have operational issues so soon. I wonder if the generator ever received a proper setup at the dealer. For a proper setup, especially on the older machines, three components must be adjusted in harmony with one another: the carburetor, the governor and the choke (when so equipped).

Though the specific steps are too detailed to list here, you can at least check the position of the choke plate: it should be about 1/4 open when the generator is cold.

Prolonged surging is indicative of a governor and/or carburetor out of adjustment. Unfortunately, the carburetor and governor should only be adjusted while monitoring the voltage and frequency and while applying a measured load at the same time. In other words, RV generators cannot be tuned by ear.

As I often state in my seminars, every mechanical adjustment on an RV generator carburetor and governor will have a direct electrical result, so I don’t condone any tweaking and twisting by RV owners. I’d recommend a generator setup by a certified technician using a properly sized load bank (see photo). Some individual RV repair facilities may have such a diagnostic load bank, but your best bet is to take it to a certified shop for your brand of generator when possible.

Also, in severe cases of varnished fuel, it may be necessary to replace the complete carburetor anyway. In the old days we used to rebuild generator carburetors; but with the newer models, replacement is the better option (in some cases, the only option).

Applying the proper setup steps using a load bank will either eliminate the surging issue or lead you to the right repair track.  

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.




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A Pseudonym
5 years ago

Good day, Doc.

Could altitude be a contributing factor indicated by those symptoms? Perhaps a different size needle is required.



5 years ago

If your carburetor is surging due to varnish, try B-12 Chemtool first. Be sure you have fresh fuel in the tank, then pour in the correct about of Chemtool. It will dissolve the varnish and restore smooth operation in many cases. It takes about 15 minutes, in my experience. I first learned about B-12 from The Car Guys, Tom and Ray, on NPR. They recommended it and they were right.

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