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mr. ed · 01-08-2005, 01:47 PM

Here's a problem I'm experiencing on my 6.5KW Onan (1990 vintage). Upon starting, particularly during damp weather the voltage starts out at about 95 VAC and very slowly climbs to normal (about 125 VAC). This takes place over a period of several minutes. Upon reaching the proper voltage, the genset operates normally. Because this problem manifests itself during high humidity conditions I'm guessing that moisture is causing a shorting problem in the coils, which gradually dry out as the genset runs OR moisture is somehow affecting the circuit board and/or associated electrical connections. I tried posting this question on the Onan Forum at Funroads.com but the forum is down at this time. Any ideas? (BTW, the frequency appears OK, around 62-64 HZ).

mr. ed · 01-08-2005, 01:47 PM

Here's a problem I'm experiencing on my 6.5KW Onan (1990 vintage). Upon starting, particularly during damp weather the voltage starts out at about 95 VAC and very slowly climbs to normal (about 125 VAC). This takes place over a period of several minutes. Upon reaching the proper voltage, the genset operates normally. Because this problem manifests itself during high humidity conditions I'm guessing that moisture is causing a shorting problem in the coils, which gradually dry out as the genset runs OR moisture is somehow affecting the circuit board and/or associated electrical connections. I tried posting this question on the Onan Forum at Funroads.com but the forum is down at this time. Any ideas? (BTW, the frequency appears OK, around 62-64 HZ).

RV Wizard · 01-08-2005, 06:35 PM

It may also be the brushes making a better contact with the rotor allowing for a less resistant path therfor a higher voltage as you have see. If you could give us a little more info on the particulars of the generator such as model & spec. # we might be better able to help.

mr. ed · 01-10-2005, 02:42 PM

Mike...thanks for the reply. The genset is a 6.5kw unit. I believe it's the Emerald model NHE-2 (I'll have to do some digging to be sure). I had the commutator cleaned last year and I believe the brushes are OK. As soon as this rain system leaves So. Calif. and the days dry out, I'll fire up the genny again to see what happens, just to be sure it's a moisture related problem. I've had a lot of work done to this unit over the past few years and I'm getting to the point where putting much more money into it may not be a good idea (maybe time for a new generator

$$$)

Ken Lenger · 01-10-2005, 05:48 PM

On my generator (Onan 3600 LP) frequency is determined by RPM and voltage is controlled by the voltage regulator board, which controls excitation to the generator windings (I hope I described this correctly). IOW, the regulator board may be defective. Could be temperature related or moisture as you described. Good luck.

mr. ed · 01-11-2005, 11:19 AM

Ken, I have that suspicion, too (along with possible moisture in the windings). The weather's now drying out here and I'm going to test the genset again in a few days. Do you know of a source for boards for these units besides Onan? (Like the boards that are available for refrigerators).

Ken Lenger · 01-11-2005, 05:24 PM

I don't have any experience with finding the boards. I assume that Onan will be the place to get it.

I have a copy of the service manual for my unit at http://www.klenger.net/arctic-fox/ge...ion/index.html. It might help.

RV Wizard · 01-12-2005, 01:32 AM

Mr.Ed, if you find that you have a control board problem the company Dinosaur does make some replacement boards for the Onan Generators. Let me know if you think you neeed a board and I can help you get one. Dinosaur does not sell to retail but I can find a local dealer for you or send one to you myself.

mr. ed · 01-12-2005, 02:08 PM

Thanks, Mike & Ken for your replies. I'm going to try the generator again this weekend, having given everything time to dry following the torrential rains here in S. Calif. I want to verify that the problem is excaberated by moisture. I've had the board out in the past to check components, clean connections, etc. I don't think I have a motor problem here, since the RPM's sound normal. Perhaps there's a governor problem? At any rate, Mike, if I need a board I'll provide you with further info as far as serial and model nos. (I have these written down at home).

Guvnor · 01-15-2005, 08:38 AM

mr. ed

You can have one of a couple of problems with your Onan. First, make sure the stator and rotor windings are neither shorted internally or to each other nor are leaking excessively to ground. If these items are OK;

Then Onan makes a retrofit called a "Voltage Build Up Kit". Onan Part Number 0300-5049, which I installed a couple of years ago on my 6.5 NHE spec P, after having developed a similar slow voltage rise symptom.

This problem occured first with my 2000 model generator after considerable camping in very humid night time conditions (condensing dew point) on Mexican Beaches.

The "Voltage Build Up Kit" consists of a small isolation transformer, plus associated installation components, that fits inside the wiring box/control panel on the generator. And is wired to isolate the voltage sensing lines to the control board. Fixed our situation immediately.

Best of luck. This will most likely be a special from your Cummins/Onan dealer to their distribution center.

mr. ed · 01-19-2005, 01:40 PM

Thanks for the reply, Guvnor. I fired the genset up a few days ago following several days of low humidity and it appeared to be working OK. I appreciate the info you provided about the add-on equipment that may solve the problem. I will keep a record of it. Thanks again....