Email of the day March 12, 2013, Pay for a Guess?


Crystal Ball

The Repair Shop’s  Diagnostic Tool?




Subject: power tech diesel – RV

from: Angela P.

 Message Body:

My boyfriend is first time owner of a 99 Dutch Star RV. We’ve read owner’s manual together, trying to figure everything out, but not much on generator. It runs for about 30 minutes to hour, then shuts off. Repairman says it’s “some kind of” sensor but can’t locate problem. Wants to send us to a dealership. We’ve already paid the repair shop so much already and have decided to try and figure out ourselves before going to a dealer. You advise buying a manual, so we will do that, but can you give us an idea of what the problem could possibly be? Ever heard/seen this problem before? Thanks for any help



George’s response.


Hats off to you for doing your own thinking, as you may have read here; it’s all too easy to pay for shop labor and receive a guess at the problem. As another bus owner found, an RV outfit was using the WRONG manual to diagnose his problem, and charged him a tidy sum.

In my opinion, I could have guessed from here and charged you way less.. or you can do your own guessing with this crystal ball off ebay..

Behind every good man is a woman so much of the time, and you are exactly on the trail of a cure for way less money. The repair manual for the gen set is a very nice thing to keep in the vehicle..  

First Step is to know who made the generator and the model and serial number. This is usually found on a name plate, and is often in plain view where you check the power plant’s lube oil lever, change the lube oil filter or air filter.

Once you get the manual, you will normally find a ‘theory of operation section’, and this is generally easier to understand than you might think. easier than learning how to sew, that’s for sure!

In this  section of the manual, the sensors are often discussed, and generators can have more than engines. It’s all pretty simple >AFTER< you know where the problem is 🙂

 Here’s what you do..

Make a list of what the Engine/generator need do. I give you some likely things, you will read the manual and learn what yours does. And do know… ‘YOU’ can fix it!

What we know, the generator starts and runs, but shuts down.

 Is there an over temperature sensor for the coolant? Is it air cooled, or water cooled? Is the coolant level low? Is the sensor only bad?

Is there a lube oil pressure sensor, is it faulty or the pressure too low?

There may be other things monitored, like over voltage, under voltage, or the generator may be running too far off frequency.

Remember, every generator owner should have a ‘Kill A Watt’ cheaper than dirt, and a good monitor, regardless what your generator panel say, it’s always nice to have a second opinion, that be the kill a watt.

Your post did make email of the day.. and we’ll all be grateful if you use comments on the blog, and share with us. We all learn that way.  There are friends of utterpower who are in the business of repairing generators and small engines that might offer you more advice, once we learn what generator you have.

A very common practice is to strap across a sensor that opens on fault, or remove the wire on one that provides a ground on fault. You only run long enough to prove the sensor is the reason it quit running, and then the next step is to determine if the sensor is good or bad.

When you do fix it, and you will.. I’d be very inclined to post your letter to the repair shop for their effort to guess at the problem and bill you.  It’s all too common, but I thought they hung people outside of Austin, Texas for such offenses, so maybe you live there?

 All the very best, and God bless Texas.. a lot of people don’t know it, but this IS the DIYer capital of the world!



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8 Responses to Email of the day March 12, 2013, Pay for a Guess?

  1. David says:

    My Father was telling me just last night about his few month old new Ride on lawnmower. It’s a JD.

    It started running bad for no apparent reason and being a mechanic and owning a car wrecking yard, he started going through things ( first off the fuel!) until he drew a blank.

    He was telling a customer he was going to take it back to the dealer as it was still under warranty when the client said he had one like that which did the exact same thing and asked if he had changed the oil?

    My father said he had changed it after 3 hours initial time as thats when all the metal shavings fall out but had not changed it since. The client said they have oil sensors that monitor the colour of the oil and if it gets too dense, the thing limits the engine power and then shuts it off all together.

    My father changed the oil which he thought wasn’t too dirty nor over due and the mower started right up and ran like a top.
    Apparently a lot of new engines are coming out with this ” feature” now.

    If the generator’s oil hasn’t been changed, might be worth giving it a go.

  2. Richard says:

    Provided that your ’99 RV has standard equipment, it should be a Onan 7500 diesel generator (check as suggested).

    Apparently the 7500 model is more or less the same as the 8000 and the manual can be found here:

    Good luck


  3. Brian W says:

    Hope you find the problem, but please do the following after you do find the problem: Post information on the internet regarding ALL the particulars of the generator and the problem you found. Many times there is a common failure mode with a particular model and year of product. You may be helping many people who Google search for the solution to the exact problem you are experiencing. I know I’m so very grateful when I find a post about something I’m trying to fix and the answer is there on the internet. Example: Chevy Silverado I own had “service trailer brake system” warning on the dash display even though I rarely pull a trailer and wasn’t any time lately. I never would have guessed it was a bad sensor on the brake master cylinder. Turns out to be a common problem on my year truck and a Google search saved me hundreds in dealer diagnostics and repair. Some poor guys reported that the dealer had no clue and replaced modules and wire harnesses when a $40 sensor was all that was needed.

    • George B. says:


      Such a truth you post, DIYers often do for themselves in order to have it done right..

    • Jetguy says:

      That manual link has the hot tip of the day, the genset will tell you what the last fault was and why it shut down:

      First-Level Fault Codes: The genset controller
      provides extensive diagnostics by causing the status
      indicator light on the Control Switch to blink in a
      coded fashion. Following a fault shutdown, the indicator
      light will repeatedly blink 1, 2 or 3 blinks at a
      • One blink indicates shut down due to high temperature
      • Two blinks indicates shutdown due to a loss of
      engine oil pressure
      • Three blinks indicates shutdown due to some
      other abnormal condition.
      Second-Level Fault Codes: For a 1-blink or 3-blink
      first-level fault code, one touch to Stop brings up a
      second-level fault code. This code consists of 1, 2, 3
      or 4 blinks, a brief pause, and then 1 to 9 blinks. The
      first set of blinks represents the tens digit and the
      second set of blinks the units digit of the fault code
      number. For example, Fault Code No. 23 would appear
      NOTE: Fault Code Nos. 1, 2 and 3 are first-level faults.
      Avoid interpreting them as second-level Fault Codes
      11, 22 and 33. The pauses between repetitions of the
      fault code are longer than the pauses between the
      tens and units digits of the the code. For example,
      Fault Code 33 would appear as:
      —longer pause—
      Restoring Fault Code Blinking: The fault code
      stops blinking after five minutes. Press Stop three
      times within five seconds to restore blinking. Note
      that the last fault logged will blink, even after the
      condition that caused the shutdown has been corrected.

      • Jetguy says:

        I’d say that is a really nice setup.
        Who’s down to make an Arduino code that does the same thing?
        A usefull add-on to any genset.

  4. George B. says:

    Jet.. good post.. It really is easy to build controllers, and far easier with the Arduino than what we DIYers had before.. a designer/developer should always note the norms. The code reader for cars and trucks, and that cheap WIFI interface.. I read and reset the codes in my truck from my Android, and once I know the code, I use the internet browser to look it up.. and perhaps that’s a good place to keep this manual if you have an RV? In a file on that 32GB card in your smart phone? What would it take to embrace this interface and use it? With the result, could we automatically grep the code from the manual and display the page on our smart phone?

    It is likely the next logical step.

    Now if the Generator were built by an entity funded by the public purse, all sensors would be duplicated, and the diagnositcs would tell you that one had been declared insane, and ‘locked out’. The system would hound you daily till you replaced that sensor, and even ask you if you wanted the step by step proceedure to replace it, or if you needed help in ordering the part 🙂

    My Neigbor’s water softener begs him to listen! “let me tell you about what I need”

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