1973 GMC 26' Glacier Build

[RF_Burns]

Checked the Onan vibration with the points and the electronic, both have a similar slight vibration so maybe the grinding on flywheel for the magnet?

Now on to next problem, swapped out my board for a new one from Flight Systems fire her up everything was fine until about the 10th time and then no start, looked at troubleshooting and 3B "is there 12v present between terminals 10 and 1", my answer was no so it states "replace K1 start solenoid" I contacted Flight Systems and sent board back. They tested and said board was fine and the only way they could duplicate problem was with remote switch in stop position. Got the board back installed and did not hook up the remote switch (top of board) hit start same problem, it will start with coil jumper wire or with jumper between 9 and 11 on board. I started investigating why I get no power to #10 and it appears to be the starter relay solenoid under the board, if I hit the starter button there is no power on the right side, would this be the culprit? it appears Cummins has the solenoid but $70 out the door so I don't want to purchase unless it is verified the problem.

Thank you all, stay warm!

So I had to do some digging around to understand the issue here. So I finally found the step "3B" referenced was in the Onan troubleshooting chart for "Engine cranks but does not start" in the Onan 6Kw Major Service manual. From the control board schematic (diagram 59 on page 46), Pin 10 provides a "Cranking" signal to pull in K3 whose NO contacts close to provide power on pin 9 (to fuel pump, ignition etc).

I note that the Onan diagram shows a secondary set of contacts (K1-I) on K1 that only provide power to pin 10. Whereas Ken Henderson's schematic/wiring diagram shows pin 10 being connected to the K1 output that provides power to the starter solenoid. Since your starter is working, that shows the main contacts in K1 are working but if you have no power at pin 10, I would check to see where the wire from pin 10 is connected to the K1 relay. If that secondary set of contacts in K1 is not providing power to pin 10, then I would try moving the wire to the main output stud of K1 (going to starter). It will be the stud with zero volts on it while not cranking.

Compare the two diagrams below (both from Ken Henderson but much easier to read than the Onan manual). The bottom diagram shows pin 10 connected to K1-I as shown in the Onan Major Service manual.

The top diagram shows pin 10 connected to the output stud on K1 going to the starter solenoid. The only issue I can see with connecting pin 10 here is the possibility of a voltage spike when starter solenoid is released... but there is a good chance K1-I would get that same spike. Its only powering a relay coil so should be no issue.

 

[ScottC]

The 3B troubleshooting was from the Flight Systems Documentation, then my dumbass for some reason thought the K1 Solenoid was one of the relays on the board (K2 or K3) so that's why I sent it back in, LOL. The #10 wire is connected to the right side (I) of K1 solenoid shows no power at any time, the left side (S) has constant 12v if the battery is connected, the left side lug to starter solenoid of course is working. This terminal (I) powers the choke also, the choke is in bad shape but appears to work with jumper still electrical connection is suspect.

 

[RF_Burns]

The 3B troubleshooting was from the Flight Systems Documentation, then my dumbass for some reason thought the K1 Solenoid was one of the relays on the board (K2 or K3) so that's why I sent it back in, LOL. The #10 wire is connected to the right side (I) of K1 solenoid shows no power at any time, the left side (S) has constant 12v if the battery is connected, the left side lug to starter solenoid of course is working. This terminal (I) powers the choke also, the choke is in bad shape but appears to work with jumper still electrical connection is suspect.

OK, as per Ken Henderson's top wiring diagram on my previous message, move the two wires from the I terminal to the lug terminal on the left side which also connects to the starter. This should give you 12V while cranking to pin 10 and also to the choke heater.

 

[ScottC]

OK, as per Ken Henderson's top wiring diagram on my previous message, move the two wires from the I terminal to the lug terminal on the left side which also connects to the starter. This should give you 12V while cranking to pin 10 and also to the choke heater.

Bruce, thank you so much for your help! I am not good at reading schematics but I do get what you are saying and will try that after work.

Thanks Again!

 

[ScottC]

Bruce, thank you so much for your help! I am not good at reading schematics but I do get what you are saying and will try that after work.

Thanks Again!

So I did try that but as I figured it's only a trigger for the starter wire

 

[RF_Burns]

So I did try that but as I figured it's only a trigger for the starter wire

That will put 12vDC on pin 10 while cranking which pulls in K3 whose contacts provides power to the fuel pump and ignition system. Once the engine starts, K2 pulls in which kicks off the starter and provides power to K3 to keep the engine running.

 

[ScottC]

That will put 12vDC on pin 10 while cranking which pulls in K3 whose contacts provides power to the fuel pump and ignition system. Once the engine starts, K2 pulls in which kicks off the starter and provides power to K3 to keep the engine running.

I was wondering if something on the board would supply power after start that is why I went ahead tried it but as stated soon as I let off start button engine stops. Tried it about 3 times and walked away.

After reading this I double checked all my connections and tried again, Whola it started and ran fine! Maybe I had a bad connection? I will mess with it later today and wiggle wires.

Thanks again Bruce! You are awesome!

 

[RF_Burns]

I was wondering if something on the board would supply power after start that is why I went ahead tried it but as stated soon as I let off start button engine stops. Tried it about 3 times and walked away.

After reading this I double checked all my connections and tried again, Whola it started and ran fine! Maybe I had a bad connection? I will mess with it later today and wiggle wires.

Thanks again Bruce! You are awesome!

The fact that it now starts, but then quits when you let off off the start button shows you are getting power to pin 10 during cranking. Something isn't good on the "Run" side.

The control board gets its "Run" signal on pin 8. This gets voltage from the flywheel alternator. There is a wire coming from upfront at the flywheel to a voltage regulator just behind the carburetor. This wire connects to a double spade connector and a second wire goes over to pin 8 on the control board. Most applications have this double spade connector disconnected from the voltage regulator and taped up to disable the battery charger feature of the regulator.

If your '73 still has a small battery for starting the Onan, this double spade should be plugged into the regulator to charge it's own battery. Most however use the house batteries to start the Onan, so if this is the case the double spade connector should be disconnected from the regulator and taped up.

In any case, check the connections at the double spade connector and at pin 8. There should a second wire coming from the flywheel alternator to the battery stud of K1. Check that wire and the connection at K1 as well.

 

[RickHaugh]

Ok here we go, we purchased this coach on Sunday August 1st 2021 just North of Columbus, OH in Delaware, OH. The gentlemen we purchased it from bought it from an Estate about 50 miles from there. The story goes that it was the deceased prior owner's pride and joy and was described as having new rims/tires, rust free painted frame, new brake lines, new macerator pump, new fuel lines, fuel tanks cleaned, painted and new sending units, good glass (no hazing), newer A/C unit, Onan generator not running, interior almost gutted, we will finish gutting it out.

Main issues (this list will get longer) are the final drive is shot, exhaust manifold and muffler leaks, roof seams leaking, windows leaking (not windshield), the previous owner removed 2 of the 3 black tank vents (WTF), removed the bath vent and put a 14" regular vent about 1 foot in front of that (WTF), there is no fridge vent on the passenger side by the door, all vents are on the drivers side and they leak also.

We have built the jack stands, got her in the air and will start by ripping the rest of carpet out due to leaks, fix the leaks, pull out the final drive so I have it for a core when I buy the 3.70.

If it has the original all electric refrigerator, it does not need the refrigerator vents neither to side vent nor the roof vent.

 

[ScottC]

If it has the original all electric refrigerator, it does not need the refrigerator vents neither to side vent nor the roof vent.

There was a 3 way Dometic sitting in it and that is what they were setting it up for, the PO was also trying to move the bathroom forward so that is why they were moving the fridge over to the galley. I have a 12v Norcold going in the original location.

 

[ScottC]

I was wondering if something on the board would supply power after start that is why I went ahead tried it but as stated soon as I let off start button engine stops. Tried it about 3 times and walked away.

After reading this I double checked all my connections and tried again, Whola it started and ran fine! Maybe I had a bad connection? I will mess with it later today and wiggle wires.

Thanks again Bruce! You are awesome!

As it turns out I think I was just not holding the start button long enough, I would let off as soon as if fired. I have to hold the start just a tad longer and she runs fine.

The thing that is confusing is the operation of the relay solenoid, it must be continuous duty? I am used to powering terminal (S) to energize the solenoid and complete circuit, the Onan solenoid terminal (S) is hot until the Start is pushed then open circuit. So if I were to look for a new non-Onan solenoid I should search for continuous duty?

Also are the flag connectors 1/8"? They appear smaller than a typical automotive blade connector.

Thanks again!!!! Hope everybody has a great weekend!!

 

[RF_Burns]

As it turns out I think I was just not holding the start button long enough, I would let off as soon as if fired. I have to hold the start just a tad longer and she runs fine.

The thing that is confusing is the operation of the relay solenoid, it must be continuous duty? I am used to powering terminal (S) to energize the solenoid and complete circuit, the Onan solenoid terminal (S) is hot until the Start is pushed then open circuit. So if I were to look for a new non-Onan solenoid I should search for continuous duty?

Also are the flag connectors 1/8"? They appear smaller than a typical automotive blade connector.

Thanks again!!!! Hope everybody has a great weekend!!

K1 solenoid terminal S is the coil winding. It is pulled to ground to activate K1 through a Normally Closed contact on relay K2 by the Start switch. When either Start switches are pressed, S is pulled to ground. When the engines starts, its flywheel alternator makes power and pulls in K2 which opens the circuit from the Start switches and K1 is released, So you can Hold the Start switch and the Starter will automatically disengage through the action of relay K2. Relay K2 also closes a contact that provides power to relay K3 which then provides power to the engine Ignition and fuel pump.

Power for the control board should be provided by Pin 11 which supplies power though the on-board fuse F1. If you have power to the board connected to Pin 5, you are bypassing the fuse. Pin 5 should always show 12V power.

The quick-connect connectors on my board are 3/16" I believe. Digikey shows 34 widths available from 0.047" to 0.375".
Here is a link to 3/16" right angled connectors, but you need a special jaw set to crimp them.

https://www.digikey.ca/en/products/detail/te-connectivity-amp-connectors/3-520339-2/288007

You many be able to use straight in-line connectors, but I don't know if there is enough clearence.

https://www.digikey.ca/en/products/detail/te-connectivity-amp-connectors/3-350816-2/288055

 

[Matt Colie]

Scott.
If you are letting the switch up as soon as you hear the machine fire, you may be beating the LOP (Low Oil Pressure) switch to close. LOP switches do go bad and one of the ways they go bad is to get slow.
Matt_C

 

[RF_Burns]

Scott.
If you are letting the switch up as soon as you hear the machine fire, you may be beating the LOP (Low Oil Pressure) switch to close. LOP switches do go bad and one of the ways they go bad is to get slow.
Matt_C

Hi Matt,
The electronics on the control board is a simple delay timer for the low oil pressure shutdown function. The timer circuit does not get power until the relay K2 closes and K2 gets its coil voltage from the flywheel alternator. So when K2 closes, the engine is spinning fast enough for the flywheel alternator to put out enough voltage to pull in K2's coil. Then there is then a 2-3 second delay before the timer circuit fires SCR CR8 which cuts the power to relay K3 through the oil pressure sensor switch itself. By then the oil pressure switch should have Opened and the delay circuit is disabled so the engine continues to run. He has a new board so the timer circuit should be working properly.

 

[ScottC]

Fixed up the battery wiring and the 120v output of the Onan.

 

[Matt Colie]

Hi Matt,
The electronics on the control board is a simple delay timer for the low oil pressure shutdown function. The timer circuit does not get power until the relay K2 closes and K2 gets its coil voltage from the flywheel alternator. So when K2 closes, the engine is spinning fast enough for the flywheel alternator to put out enough voltage to pull in K2's coil. Then there is then a 2-3 second delay before the timer circuit fires SCR CR8 which cuts the power to relay K3 through the oil pressure sensor switch itself. By then the oil pressure switch should have Opened and the delay circuit is disabled so the engine continues to run. He has a new board so the timer circuit should be working properly.

Thanks Bruce,
Than was merely what I surmised when my Onan. I put an LED across the lop switch to see when it closed. So, I added a couple of seconds to my start cycle. I seems to have worked for me.
Matt_C

 

[ScottC]

Just finished up insulating the inside of a later model generator box for the Onan (ours had the wood box).

 

[pvfjr]

Just finished up insulating the inside of a later model generator box for the Onan (ours had the wood box).

Looks tidy. What type of insulation did you use? Does it have a temp rating? My PO insulated my gen box, but it's beginning to fail and come apart. I don't know whether moisture, temp, or time was the biggest factor. It was that foil-faced semi rigid fiberglass stuff--I think they call it duct board?

 

[ScottC]

Looks tidy. What type of insulation did you use? Does it have a temp rating? My PO insulated my gen box, but it's beginning to fail and come apart. I don't know whether moisture, temp, or time was the biggest factor. It was that foil-faced semi rigid fiberglass stuff--I think they call it duct board?

Nothing special just some stuff from Amazon looked around for stuff with a decent rating, adhesive was very tacky and the aluminum was a little thin but I will just patch if needed. Link is below.

I did purchase 2

Amazon.com

 

[ScottC]

Another Onan question: I am planning on running a 30A setup due to the fact I am only running 1 A/C unit, 12v only fridge and on occasion a microwave, I already have a 30A cord and extension. There is currently a 30A Atwood Box/Charger onboard and I plan on swapping to a Victron Energy Multiplus II, The Onan is a 6000K 50A, should I run one hot leg to the Victron and the other hot leg to electrical panel to a dedicated breaker for A/C and Microwave or just not use 1 leg?