Subject: gmc: onan generator Output

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Date: Tue, 06 Jan 1998 20:10:01 -0500

From: John Massey

Subject: GMC: ONAN Generator Output
I have a 1977 Royale and we are finally back at home after being out for about three months. I was checking out my batteries and decided that while the weather was nice I'd run the generator for an hour which I do each month. I rarely use it since generally have shore power.

While it was running I decided to check its output with my digital voltmeter and got a disturbing reading. With a 1500 watt load it was putting

out 145 V ac, removing the load, it went to 155 V ac. Checked the meter against the shore power and it read 115V ac. What gives?

During the past months I've used the generator several times to power the TV and electric heater with no problem.

I've got the GMC in August and one of the things I do not have is an Onan owners manual.

John Massey

From: Ralph Edelbach


Date: Thursday, April 30, 1998 4:52 AM

Subject: GMC: Onan tips and reading lamps??
>When we bought our '74 Glacier in January, the 4 KW Onan started from both inside control panel and by using the start switch on the unit. A few weeks ago I tried and didn't have any luck. Same problem yesterday.


>Symptoms: Upon depressing the start switch on the unit, I get a few seconds of a soft, dull clicking sounds which stops even though the start switch is still depressed. If the switch is released and pressed for a second time or more, the noise occurs again. After charging the battery last night, it is doing the same thing this morning.


>Since I'm planning on taking it to the vintage sports car races at Summit Point, West Virginia in a few weeks and they have no hookups, I'd like to have power if possible. If not, I'm still going but will have to rough-it a bit more. Just like the "goode olde days."


>Looking at the GMC maintenance manual, I see how to checkout the "no cranking" condition by jumping various terminals on the PC board and I will do that in the few days but I assume the noise is either the fuel pump starting and then shutting off since the carb float chamber is probably full or the fuel solenoid valve opening as I'm attempting to crank the unit.


>Any other "hot" tips to look at if the terminal jumping doesn't work??

Thanks for the info.


Ralph..........First thing, check the battery terminals and make sure they're tight. Check and make sure you've got a good ground. It could be as simple as this! Take a look at the small high intensity reading lamps in the stores or even garage sales. They all have a transformer that reduces 110 to 12 volts. Throw the transformer and base away and mount the rest of the lamp anywhere you need it. They even come in different colors to co-ordinate with your GMC.

Jim Davis

Date: Thu, 30 Apr 1998 21:40:55 -0500

From: "Russ Bethel"

Subject: Re: GMC: Onan tips and reading lamps??
Had a similar situation today. Found that I was not getting steady voltage from the battery to the Onan. I replaced the battery cable to the Onan and everything was fine as far as cranking. I could not get it to start though and found that the points had corroded. After changing the points and condenser everything worked fine.

Russ Bethel

1976 Glenbrook

Date: Sun, 03 May 1998 16:17:22 -0400

From: "Ralph D. Edelbach"

Subject: GMC: Onan starter
I discovered that the problem with my 4000 Watt Onan is that the heavy lead coming out of the solenoid and going through the starter case is broken. When I disconnected it to clean the terminals, it came off in my hand. Just the connector to attach the line to the solenoid and about 1 inch of line. I'm going to try to get the starter off with out taking too much off the engine but if I remember correctly, the manual says to remove a bunch of stuff. At least it isn't a major engine problem.
Strange but the wire broke with the coach sitting in my drive-way. I started the Onan a few times after buying it in January but haven't had it on the road except for a 10-mile trip. Guess it was just time for the wire to break. Better in my driveway than on a long trip.

Date: Sun, 3 May 1998 16:37:07 EDT

From: RickStapls

Subject: Re: GMC: Onan starter

Must be a Bosch starter. Used to see same thing on VW Beetles: wire into

starter just corrodes away. Worst of all, the heavy braided copper wire is spot welded to the field coils inside the starter. Time for a rebuilt starter. I'm gonna check mine and apply grease or WD40 or something to the wire.

Rick Staples

Date: Wed, 06 May 1998 13:05:43 -0400

From: Ralph Edelbach

Subject: GMC: Onan starter
Thanks to anyone who might be working to provide me with some information about my Onan 4KW starter problem but I just found a new unit at Golby's for $201 plus shipping so I'm just glad that I didn't have to junk the whole unit. A local Onan distributor could get one from the warehouse in a week or so but their price was $223 plus shipping.

Thanks again.

Date: Thu, 14 May 1998 22:34:18 -0500

From: "William D. Minor"

Subject: Re: GMC: synthetic oil in Onan
I use Castrol Syntec in my 4.0 Onan. It definitely cranks better and appears to run cooler and with more power. I also added a flap on the lower to prevent hot air from recirculating while camped to help with the cooling.

Bill Minor

'73 GMC 230 Sequoia

Date: Thu, 21 May 1998 17:40:07 -0600

From: Robert Shimanek

Subject: GMC: ONAN 6KW Starting Problem
Acuating the rocker switch at the Generator Control Panel or remote switch inside the coach

Problem is as follows:

1. Push to start switch, engine tries to fire (like on one cylinder) and starter drops out immediately. This continues to repeat the cycle until you release the switch.
2. Jumped terminals 9 & 11 on generator terminal board and engine ran normally indicating K2 relay contacts are defective.
3. Checked K2 relay operation on the bench by applying 12 volts to relay coil. Relay operated normally. Checked the contacts for continuity which were OK no resistance.
4. Also checked K2 relay operation and continuity which were also OK.
5. Checked for operation fuel pump, electric choke, and fuel solenoid which were OK.
6. Needed points, condensor, plug wires and plugs so I changed them even though the engine ran when terminals 9 & ll were jumped.
7. Connected wire from battery ground to starter solenoid. Engine started and operated normally. Noted that the K2 & K3 relays operated normally.
8. Checked Alternator DC voltage output which was 14.1 to 14.2 which would cause K2 to operate and keep K3 relay closed for continued engine operation.
9. Checked the generator board for PC board cracks and continuity along with the wiring on the board.
10. I hate to replace the board for $120.00, if I am missing something.
11. Little background that I had last weekend. Before I left my home I checked the generator for operation being that the coach is stored inside for the winter months. Engine and generator operated normally.
12. I traveled approximately 350 miles to my destination in lower Michigan. When I went to start the generator from the remote switch in the coach--the unit would not start I pulled the generator out and it started from the generator panel & ran normally after a couple of attempts. This happed once before a couple of years ago.
13. I kept the unit operating for approximately 4 hours with the top air conditioner operating. (98 degrees outside)
14. When I left the parking lot I had my wife shut down the unit from the remote switch. She said all indications on the panel after holding down the switch in the stop position that the unit was shut down. She has accomplished this task many times with no previous problems.
15. However, when I arrived at the campsite I noticed the generator was operating again so she shut it down again as before.
16. Now during the night 2:30AM a loud banging was coming from under the rear of the coach near the generator (That was a quick wakeup). To my amaze the generator was trying to start itself. So I immediately hit the remote stop switch in the coach and the unit stopped trying to start.
17. Looking for suggestions from the experts to correct this problem.

Maybe the problem is in front of me and I can't see.
Will appreciate your help


Date: Thu, 21 May 1998 23:12:31 -0700

From: Jim Bounds

Subject: Re: GMC: ONAN 6KW Starting Problem
I am impressed that you followed such a logical testing procedure, most people would stop and fork out the bucks for the board without further investigation. In this situation, with the unit starting OK from the side, it looks like the PC board may be working. If you have no operation on the remote, the chassis ground to generator, wires to the remote, or the molex connector may have problems. I would run a 4 ga. wire to ground then to the generator block first. Then check continuety of each wire to the remote circuit.
Let me know what fixes it.

Jim Bounds www.gmccoop.comRobert Shimanek wrote:

Date: Fri, 22 May 1998 15:29:39 -0600

From: Robert Shimanek

Subject: GMC: To correct Onan varied voltage problem.
1. Before making adjustments run the generator about 15 minutes under a light load to reach normal temperatures.
2. Engine speed determines the output voltage and current frequency of the generator.
3. Increasing the speed increases the voltage and frequency and vice versa.
4. An accurate voltmeter should be connected to the generator output. I used one of the receptacles in the motorhome to check the voltages.
5. A binding in the bearings of the governor shaft, in the ball joint or in the carburetor throttle assembly will cause erratic governor action or alternate increase or decrease in speed hunting. A lean carburetor adjustment may also cause hunting. Springs have a tendency to lose their calibrated tension through fatigue after long usage. If all governor and carburetor adjustments are properly made and the governor action is still erratic, replacing the spring with a new one and resetting the adjustments will usually correct the problem.
6. Speed Adjustment----With the warmed up unit operating at no load, adjust the tension of the governor spring. This is located on top of the unit and is connected to an arm with small drilled holes near the shaft.(You will see a spring with an adjustment nut. This adjusting nut is turned to obtain a voltage and speed reading within limits.)
7. Sensitivity Adjustment---Check the voltage with no load and with a load.
8. Adjust the sensitivity to give the closest regulation (least speed and voltage difference between no load and full load) without causing a hunting condition.
9. To increase the sensitivity (closer regulation), shift the spring toward the governor shaft. That may be one hole closer to the shaft.
10. An adjustment for too much sensitivity will cause alternate increase and decrease of engine speed (hunting).
11. To decrease sensitivity, shift the spring toward the outer end of the governor arm. Too little sensitivity will result in too much difference in speed between no load and full load conditions.
12. Now any change in the sensitivity adjustment usually requires a corresponding spring (spring tension) adjustment.
Maximum Voltage No-Load-----126 VOLTS
Minimum Voltage Full Load--110 VOLTS
Hope this helps you out.



Date: Sat, 30 May 1998 18:53:54 EDT

From: (David L. Greenberg)

Subject: GMC: Battery Boost switch
Be careful. Early models didn't have a rocker switch for the battery boost and sometimes the switch is left in the boost position or on. GM later changed this to a rocker switch. You only use this to put all batteries together to help start your engine or Onan. Not to be used (and unnecessary) while the engine is running.

David Lee Greenberg


Date: Sun, 31 May 1998 21:21:23 -0700

From: Jim Bounds

Subject: Re: GMC: 4000w onan generator
Robert Teed wrote:


> I know nothing about My Generator...When I open the door to the Generator I see an old Battery with cables and a green steel box with what appears to be a bent wire handle with the word " Release " and an arrow below it. Sliding this handle to the right does what? Should this allow the steel box to "open" from the front? Should the steel box "Slide" out? How do I access the Generator motor? I know I can get all this info from Cinnabar but I'm on a tight budget right now.

> Thanks,

> Rob Teed

> 74 Painted Desert

Well, you are on the right track, you have eyed that green thing in the back correctly as your generator. You would probably do well to get the factory service manual which will carry you further in understanding the workings of the generator. The manual is available through Cinnabar.
As far as the operation of your 4K genny, does it start? If it starts, then shuts down, check the oils located on the lower left inside corner of the unit as you look at it. This would be the unit detecting a low oil situation and shutting the ignition off as protection. If it tries to start but will not catch, jump pins 9 and 11 on the PC board. This bypasses the operation of the PC board, if it now starts you have electrical woes. If not, pull off the rubber tube going to the carb. and spray a little starting fluid down its throat. If it sputters and tries to start, your trouble is fuel related.
This will get you started, if you need to go further, give me a call at work 1-877-275-4462.

Jim Bounds

Date: Tue, 2 Jun 1998 16:41:48 -0700

From: "Heinz Wittenbecher"
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