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Discussion Starter · #1 ·
Hi All,

I'm new here and I've been having trouble fixing a Coleman Powermate 1850 (PM0401850). It runs fine and produces enough current to power small things like a drop light, but as soon as I try and run something that needs more current, it doesn't seem to work right. Depending what I'm trying to use, sometimes it doesn't work at all or seems to half work.

I've watched a bunch of videos for troubleshooting and done continuity tests that all seem to check out. I replaced the capacitor that is on the output of the rectifying bridge since it measured low and was inexpensive. I've also replaced the A/C circuit breaker. Using a multimeter, both of the A/C outlets measure 123 to 127 VAC. I also tested the outlets using an outlet tester that will show if things are wired incorrectly and has a GFCI tester. As soon as I plug the outlet tester in, I get a green light indicating everything is good. After a second or two the green light will go away and sometimes a faint red light comes on indicating "bad ground." If also tried to trip the breaker using the GFCI tester and that doesn't seem to working either.

I haven't been able to find a schematic for the power generator which may be helpful, just the owners manual. I'm wondering if the outlet itself could be on the way out which is why it partially works. I haven't been able to find a replacement outlet online yet. From what I understand, if the issue is anything in the actual power generation system is bad, the generator is basically junk.

Thanks
 

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Coleman Powermate 1850 (PM0401850)
That generator is only rated for 1500 watts = 12.5 amps continuous. I have circular saws that draw more than that. I had a PM1500 that was similarly easily overwhelmed by motor loads, but could easily support incandescent lighting up to its rated continuous load. Power drills and recipro saws were in the sweet spot, though.
 

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Two things:

1. Your A/C is probably overloading your gen. You didn't say how big it is in terms of BTU/h or Wattage/Current (start-up and running). The smallest window A/Cs I've seen takes 400-500 running Watts, but would easily spike to 4-5 times that when the compressor kicks in.

2. To use plug testers, you must understand how the gen is wired. The test is mostly apt for testing receptacles in buildings and homes as they need to comply with certain electrical codes and whatnots. Generators more often than not, will fail the test, depending on a few factors such as grounding and/or the presence of neutral-ground bonding. However, failing the plug test doesn't necessarily mean it won't power up your devices. But you're on the right track looking for a schematic.
 

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Discussion Starter · #4 ·
Thanks for the replies! I understand that the generator isn't rated to provide enough power some equipment that can normally be run from a standard 15 amp wall outlet. Some equipment that doesn't work well now, used to work just fine on this same generator and that's why I think there's a problem with it.
2. To use plug testers, you must understand how the gen is wired. The test is mostly apt for testing receptacles in buildings and homes as they need to comply with certain electrical codes and whatnots. Generators more often than not, will fail the test, depending on a few factors such as grounding and/or the presence of neutral-ground bonding. However, failing the plug test doesn't necessarily mean it won't power up your devices. But you're on the right track looking for a schematic.
I suspected that the outlet tester may not work properly. I definitely didn't ground the generator to earth nor grounded the equipment to the generator using the generator ground lug. I have a "Watts Up" meter at work that I'm going to borrow. This will easily tell me the real time volts/amps/hz and hopefully that will give me more insight.
 

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50 years ago (plus or minus) I worked at the Agtronics factory in kearney, nebr... coleman bought that place out. if memory serves me, that gen was excited by a full wave bridge parallel with the output...could be a bad rectifier....(full wave bridge)..you might check that...
 

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Pondering on a possible cause of an issue where voltage is ok but current is low, my initial hypothesis is the alternator has two coils connected in parallel. One of the coils is open. You mentioned you checked. I assume the check was Hot to Neutral at an outlet. There will be continuity but at double the resistance if one of two coils is in an open condition. Did you check the coils at the connection block in the Alternator itself? If a variant of that model were marketed in a 220 50hz country, it would be a simple matter to put the coils in series and reduce the RPM for a 50hz output. This of course reduces the wattage the engine can power a little. Funny thing is, I looked for and found a 1800 watt 220v version of a Coleman Powermate. Good luck with the issue.
 

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Discussion Starter · #7 · (Edited)
50 years ago (plus or minus) I worked at the Agtronics factory in kearney, nebr... coleman bought that place out. if memory serves me, that gen was excited by a full wave bridge parallel with the output...could be a bad rectifier....(full wave bridge)..you might check that...
You wouldn't happen to have a schematic?
Pondering on a possible cause of an issue where voltage is ok but current is low, my initial hypothesis is the alternator has two coils connected in parallel. One of the coils is open. You mentioned you checked. I assume the check was Hot to Neutral at an outlet. There will be continuity but at double the resistance if one of two coils is in an open condition. Did you check the coils at the connection block in the Alternator itself? If a variant of that model were marketed in a 220 50hz country, it would be a simple matter to put the coils in series and reduce the RPM for a 50hz output. This of course reduces the wattage the engine can power a little. Funny thing is, I looked for and found a 1800 watt 220v version of a Coleman Powermate. Good luck with the issue.
I believe I checked the coils seperately, this of course was using videos online that always weren't accurate to the model generator I have.

I did some more testing and got results I halfway expected. For testing I plugged a small portage electric heater (700w), a bench grinder (300w) and a portable LED light (100w). 1100 watts is still well below the 1500 watt continuous load this generator is supposed to be capable of supplying. When I had everything plugged in and running at once, the "watts up" read that everything was drawing 7ish amps. The problem was that the A/C voltage dropped to between 85-95 and never went back over 100 volts for the 5 mins or so I let it go. The generator only seemed to supply 700 watts total. This would indicate the generator can't supply the needed amperage so the voltage drops. Could I be overlooking the perfomance of the engine? From what I understand, the generator is set to run at a specific RPM based on what frequency A/C you need.
 

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Discussion Starter · #9 ·
Easy to test for that. Just read the Hz on the Watts Up and see if it is falling off. It should be staying at about 58-62Hz.
Good Point! Unfortunately the watts up meter doesn't show hz like I thought, neither does my crappy multimeter. I have a good fluke at work I can bring home that measures frequency, I'll have to do that in the next couple days.
 

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Discussion Starter · #10 ·
Welp, I checked the frequency under load and with no load. It was a touch high at 63hz but stayed pretty consistent with varying amounts of load. The only exception was the instantaneous change in load which seems acceptable for the generator to need a second to catch up or slow down.

Back to the drawing board as to why the generator can’t supply enough current…
 

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Double-check the actual value of the capacitor against the factory-defined value. Typically, when the capacitor value has drifted lower, the output voltage goes low as well. Otherwise, there may be other issues with the gen (stator, exciter, and/or field windings).

Side note: I got confused in my earlier reply and thought you were running an air conditioner from your 1500W generator. Customarily in electrical-speak, "AC" stands for Alternating Current, while "A/C" often means air conditioner.
 

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Hi All,

I'm new here and I've been having trouble fixing a Coleman Powermate 1850 (PM0401850). It runs fine and produces enough current to power small things like a drop light, but as soon as I try and run something that needs more current, it doesn't seem to work right. Depending what I'm trying to use, sometimes it doesn't work at all or seems to half work.

I've watched a bunch of videos for troubleshooting and done continuity tests that all seem to check out. I replaced the capacitor that is on the output of the rectifying bridge since it measured low and was inexpensive. I've also replaced the A/C circuit breaker. Using a multimeter, both of the A/C outlets measure 123 to 127 VAC. I also tested the outlets using an outlet tester that will show if things are wired incorrectly and has a GFCI tester. As soon as I plug the outlet tester in, I get a green light indicating everything is good. After a second or two the green light will go away and sometimes a faint red light comes on indicating "bad ground." If also tried to trip the breaker using the GFCI tester and that doesn't seem to working either.

I haven't been able to find a schematic for the power generator which may be helpful, just the owners manual. I'm wondering if the outlet itself could be on the way out which is why it partially works. I haven't been able to find a replacement outlet online yet. From what I understand, if the issue is anything in the actual power generation system is bad, the generator is basically junk.

Thanks
First, your GFCI tester will only trip out GFCI outlets or breakers, which is not what your gen has. Secondly, you were right to replace the old cap. But you should check the Bridge rectifier too. If it's a bridge (4 terminals) you take it completely out of the unit and use a 12 volt battery (with a fuse for safety). You run the 12 volts into the AC inputs of the bridge and connect a small light bulb to the outputs. It should light up. Now reverse the battery wires. The bulb should light up this way too. If the bulb fails to light with either connection, or if the fuse blows, your bridge is bad. If you have single diodes (like my 4000 watt power mate), they will have only 2 terminals. Disconnect one terminal to isolate the diode. Using your fused battery, try running power through the diode to power your light bulb. Whether it lights up or not, reverse the battery wires and see what happens. A single diode will only conduct IN ONE DIRECTION ONLY. If it doesn't conduct at all or if it conducts both ways, it is bad.
The other thing to check is the brushes, These power the rotor's electromagnet. If they are worn down enough that they no longer make good solid contact with the slip rings, you will not be able to get enough power to get a strong enough magnet to generate the higher outputs. Make sure the brushes are moving freely and have not reached the end of their travel.
 
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