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Generators & Motors General Discussion Antique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Motors General Discussion

Coleman Generator problem, low voltage


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  #1  
Old 09-30-2008, 02:30 AM
goatchay goatchay is offline
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Default Coleman Generator problem, low voltage

Hi, newbie here. I just purchased a generator from someone off of craigslist here in Houston (16 days without power and counting). Well, I guess I got ripped off. The guy said that the generator was hard to start, but put out the correct voltage when it was running.

The generator is a Coleman Vertex 7500. It is electric start with no pull start backup, and had a dead battery, so I was unable to test it. The guy seemed honest enough and I was desperate, so I bought it.

Got it home and it was hard to start, like the starter couldn't overcome the compression on the compression stroke. It is a Briggs 14.5 horse vertical engine BTW. Anyway, I adjusted the valves to .004 and it starts up fine now.

Only problem is that is only puts out about 65-70 volts. I have changed the brushes. Checked both diodes and the capacitor and they all read fine. But still only 70 or so volts. Any advice would be greatly appreciated. Many thanks in advance,

Chris
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  #2  
Old 09-30-2008, 03:16 AM
Wayne 440 Wayne 440 is offline
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Default Re: Coleman Generator problem, low voltage

First check the engine speed, it should be around 3600 RPM. (about as fast as a lawnmower "wide open") If the speed is low, the voltage and frequency will be also. If it is equipped with one of those no-load idle devices disable or remove it.


How are you "reading" the capacitor? A simple VOM test is often misleading in this case, the value is fairly critical.
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Old 09-30-2008, 04:01 AM
goatchay goatchay is offline
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Default Re: Coleman Generator problem, low voltage

Hi Wayne, thank you for such a quick response. The engine seems to be running at WOT, but I have no way other than by ear to judge that. But it is running smoothly, not missing, etc. It doesn't have a muffler so it is LOUD, which may make it seem like it's running at full throttle when it isn't.

But I've got a similar 14 hp Kohler on my Snapper and it sounds about the same. Can just a couple of hundred rpm's make a difference? This generator does have the idle control function. I'm pretty sure I had it switched to off when I checked the voltage. Will it give a different reading depending on if the idle control is engaged or not?

I plugged a droplight into it and it barely made the filament glow.

I also found a small potentiometer inside the endbell that I think is for voltage adjustment. It is set in the middle of it's range. I haven't tried to turn it yet.

Regarding testing the diodes and capacitor, I got an infinity reading one way and a value (I can't remember what it was exactly) when tested the other way. I thought that indicated that they were good. I didn't know that the value itself is critical.

I also took it to an authorized Coleman generator repair shop and the tech also tested them and said they were good, for whatever that's worth.

Anyway, I've been troubleshooting this thing for over a week now and it's getting frustrating. Thank you for all of the help, any more direction would be greatly appreciated.

With my luck, the power will be restored by the time I get this fixed

Also, someone told me that there could be a short in the winding or rotor?? I'm not very knowledgeable about generators unfornunately. Thanks again,
Chris
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Old 09-30-2008, 08:11 AM
Wayne 440 Wayne 440 is offline
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Default Re: Coleman Generator problem, low voltage

I was thinking about a simple capacitor excited generator end, if your has a voltage regulator the capacitor value may not be as critical. Forgive me for some of the following; all of it is generic as I'm (obviously) not familiar with your specific model and personal skill set.

A conventional diode should show a low resistance one way, and very high the other when checked with a conventional analog meter.

A good capacitor will make a conventional VOM "kick" to a low resistance then gradully return to a nearly infinite reading when tested either way. The kick is proportional to the capacitor value, vary small values won't kick, they immediately show high both ways.

Since your set has a voltage regulator, it is now the likely suspect, assuming the engine is running at close to the right speed. Shut off the idle control while testing, and use a more substantial load, such as a toaster.

Turn the pot you found, it probably won't do any good, but likely can't hurt anything either. Put it back about where it was if the voltage doesn't come up to normal or close.

What did the "authorized" shop say was wrong?

Where are you getting the 65 volts? - at a "120" outlet or "240" outlet?

What are the brush leads hooked to? How many does it have?

Finally, if it needs a rotor or stator, the cost may be more than its value.

This thread might be relevant- http://www.smokstak.com/forum/showthread.php?t=51571
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Old 09-30-2008, 08:47 AM
K D Redd K D Redd is offline
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Default Re: Coleman Generator problem, low voltage

If youi have a Briggs dealer close you can buy a VIBRA-TACH to check the engines RPM. The Vibra-Tach is not very expensive.
The specs for the valve setting is .002 to .004 inches on the intake and .004 to .006 inches on the exhaust. I set them at .003 and .005 inches. The de-compression release is on the intake. If this valve is loose this will cause the hard cranking.

Kent
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Old 09-30-2008, 09:09 AM
Randy.ab9go Randy.ab9go is offline
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Default Re: Coleman Generator problem, low voltage

Sorry to hear about your problem and that some jerk took advantange of your misery. Coleman Powermate is now out of business as of March 08. Spare parts will be limited to dealer stock on hand. You may have to call around to find a regulator for your set. Try a google search. This may be your best bet. Make sure that the bearing in the end of the gen is well maintained with hi temp grease. This is the fatal flaw on Colemans. If that bearing gets hot, it WILL melt the end bell and destroy the generator. If you can locate a new regulator for a reasonable $$$, fix it and use it for something non-critical. I would not resell it. Colemans will let you down when you need them the most.

Randy AB9GO

p.s. I do have a service manual that covers most Colemans, but none show a voltage regulator, just the simple diode and cap circuit.
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Old 09-30-2008, 03:06 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Coleman Generator problem, low voltage

My union hall bought a Colemans, to run power for a rat baloon during a picket line. It lasted about 6 uses (about 4 hours at a stretch) when the plastic cam in the B&S engine decuded to lose stop turning. The dealer says it will cost more to fix it than the cost of another unit! I told the hall to buy a honda - Quieter, makes more power, will last a long time (as long as you change oil regularly), and is very dependable. BTW, the Coleman unit had plenty of oil, and fresh fuel, when it quit.
Andrew
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Old 09-30-2008, 04:46 PM
Randy.ab9go Randy.ab9go is offline
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Default Re: Coleman Generator problem, low voltage

I have never seen a plastic cam in a B&S. Granted the newest one I have had the bottom off of was 5 - ‎‎10 years old. I did see a plastic cam in a cutaway model of a Stihl 4 stroke weedeater though. Stupid ‎plastic. Stupid manufacturers! I'd look for an older B&S of the same series and rob the cam out of it. Many mower shops have a bone yard and will sell one for a few $$. ‎They are not difficult to replace and even new the cams are not that expensive.‎

Randy AB9GO
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Old 09-30-2008, 10:25 PM
goatchay goatchay is offline
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Default Re: Coleman Generator problem, low voltage

Thanks for all of the input guys. Unfortunately I threw my back out this morning and I'm mostly beridden--hadn't been able to continue troubleshooting the generator. Hopefully I'll feel OK tomorrow.

Wayne, thanks for the additional info on testing the diodes, I'm far from an expert on any of this. I'll recheck them according to your method. I'll also try a heavier load on it other than the light bulb.

The authorized shop does Coleman warranties, etc. He basically just said some major must be wrong because the cap and diodes checked out. He didn't have the entire generator, just the endbell with the diodes, cap, and pot.

It has two brushes and they are located in the endbell. BTW, I was reading the voltage at all 4 of the 120 outlets, didn't try the 220.

KD thanks for the tip on the vibra tach. There is a Briggs dealer walking distance from me and I am on good terms with them, I may even be able to borrow/rent it.

Thanks for the spec on the valves also. I got the .004 from a video on Youtube. Seems to have alleviated the hard cranking problem for now. I'll go back and reset the clearances if I can ever get this thing the put out the correct voltage.

Randy, thanks for the tip about the roller bearings, it hadn't occurred to me to grease them, I've just been so focused on the electrical side of things. I'll try and see if I can find the schematic for this thing, regarding the regulator.

It is in the base of the endbell, there is a clear plastic cover the houses the brushes and capacitor. A couple of inches away is a small housing with the pot, you can access the pot through one of the vents in the endbell, so that it can be adjust without removing the endbell.

Wayne, thanks also for the reference to the other link. I have not tried flashing it because the tech said it would be a waste of time, not sure that I understood his explanation as to why it wouldn't be helpful, but he seemed sure of it.

He did tell me that it is an "old" style version of this generator and that the new one had a board in it with the capacitor, this one doesn't.

Well, I just tried to post a link to the manual and schematic for this generator and can't access the powermate website for some reason. I have been on there numerous times all week, now nothing. There was a comprehensive parts breakdown on there.

On a side note, when all of this is said an done, I was going to try to buy a new generator for next years hurricane season. Are parts readily available for the harbor frieght type chinese units?

I bought a 6.5 hp Honda knock off from them and it has been the best motor I've ever had, especially for $129. It's run at least on hour a day for the last 6 months without even a hiccup. I've got the actual Honda version of that motor on my pressure washer and it's been tempermental from day one.

But I realize that the generator head on the harborfrieght units might not be of decent quality. Just wondering if anyone had any opinions. Thanks again to all and I'll try and see if I can find the link to the parts breakdown.

Chris
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Old 10-01-2008, 12:05 AM
Don Smith
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Default Re: Coleman Generator problem, low voltage

If your unit is like my coleman here, it has two brushes at the rear end of the generator contacting two flat circle rings on end of the armature. These brushes are for the field and provide dc voltage into the armature for magnetism. These brushes are fed by a bridge or diode set to rectify the ac voltage generated by the windings. There is also a capacitor across the brushes to filter the dc going to the brushes. Measure the dc at the brushes and check to see that the capacitor is doing its job of filtering. The low voltage could be from a bad capacitor, bad diodes, bad connections at the brushes. You could even try connecting another capacitor across the brushes from the outside. One time we had to increase the capacitor on a 5 kw unit to give the generator enough field dc power to start a washing machine motor Hope this helps Don
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  #11  
Old 10-01-2008, 05:01 PM
Randy.ab9go Randy.ab9go is offline
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Default Re: Coleman Generator problem, low voltage

You can go here to look at the Powermate website:
http://web.archive.org/web/*/http://www.powermate.com/
Unfortunately, the contract for the webhosting has expired and the site is now gone forever.

If you have a tool from one of the following you may be out of luck too. Powermate was a contract manufacturer for many brands. Some of those were Durabuilt, Marshalltown, Husky, and Kobalt. The Powermate owned brands were: Powermate, Coleman Powermate, Endura, Black Max, Industrial Air, Magna Force, ProForce, Progen, Sanborn.
I have a Sanborn compressor pump that was found by the curb 25 + years ago. It has been on 3 tanks (the current tank was found by the curb too!) and still working fine, but it was before Powermate purchased them.

Randy AB9GO
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Old 10-02-2008, 11:16 AM
FarmallBob FarmallBob is offline
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Default Re: Coleman Generator problem, low voltage

Chris - A few comments based on personal experience with several Powermate generators.

1 – If it’s a brushless unit, output voltage is critically dependent on the capacitance value of the large internal capacitor(s). One of my brothers had a 12.5 KW Powermate which suddenly developed low voltage problem (65 volts at the 120 volt outlets). Problem turned out to one of the two of parallel-connected capacitors had failed open circuit. Replacing the bad cap with a new one solved the problem.

2 – The 2.5 KW brush type Powermate at our vacation cottage was struck by lightning years ago. The hit destroyed all the components/wiring inside the end bell but not the stator/rotor windings. I replaced a pair of exploded diodes with new ones from Radio Shack - just guessing at the voltage/PRV rating required. I then installed a new 120 volt outlet and rewired it. The thing has since worked fine for 10+ years now. (Note I didn’t bother replacing the small RF surpression capacitor – the generator is used only to run power tools and the house water pump)

3 – I picked up 2.5 KW vertical shaft Powermate on the side of the road on trash day. It started/ran fine but would make only about 20 VAC at the outlet. Upon removing the generator head cover I discovered the cooling fan had worked loose from rotor and nicked a stator wire before falling off completely. I carefully peeled back the ends of the nicked winding then solder spliced the wires back together. The generator now makes 122 VAC with a test load (ancient 1200 watt waffle iron…) on line.

4 – I have a 4 KW Powermate for emergency power at my house. It’s cheaply built as are all the other Powermates. However it’s served me flawlessly for 17 years of backup use (probably 150 total running hours).

---

Quote:
Originally Posted by goatchay View Post
On a side note, when all of this is said an done, I was going to try to buy a new generator for next years hurricane season. Are parts readily available for the harbor frieght type chinese units?
Not likely repair parts are available. Rather I consider HF equipment like that to be strictly "throw away". When it breaks down simply plan to dump it and buy new.

...FB
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  #13  
Old 10-03-2008, 11:43 AM
Randy.ab9go Randy.ab9go is offline
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Default Re: Coleman Generator problem, low voltage

Are parts readily available for the harbor frieght type chinese units?

I have purchased several items from Harbor Freight and had one break. They did supply a replacement part for free, but it took 6 weeks for it to arrive. Are parts available? Yes, at least for a time and they did not rob it from another unit. Are parts readily available? It depends on how you define readily. My father-in-law purchased a small 2.5 hp gas china engine powered pump @ Harbor Freight 2 years ago and frequently (maybe 100 hrs) used last year and 1/2 has much this year. Starts on the 2nd pull, runs well and has been trouble free. Just like any Japan or clone OHV engine before winter add Stabil and drain the carb bowl (use that little drain screw!) and it will start easy every time.

Randy AB9GO
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