I have a coleman 5000 that won't hold voltage at 110 volts under load. It fluctuates up and down. The motor is running steady. What could be the cause of this?

It is most likely the low voltage alarm. Suggest connecting when the car is running with no load (110 volts not connected). If the alarm continues turn the unit off and on to reset.

Hope this helps?

Inverter Protection Features
• Short Circuit Protection. The inverter will automatically shut down until short is removed.
• Low Voltage Alarm. An alarm will sound when the voltage from the battery discharges to 10.5 +/- 0.5 volts DC. This is an indication that the battery needs to be recharged.
• Over Voltage Protection. The RED LED Indicator Light will illuminate and the inverter will automatically turn itself off when the input exceeds 16.5 +/- 1 volt DC.
• Under Voltage Protection. The RED LED Indicator Light will illuminate and the inverter will automatically turn itself off when the input is less than 10.0 +/- 0.5 volts DC.
• Overload Protection. The RED LED Indicator Light will illuminate and the inverter will automatically turn itself off when the continuous draw of the equipment being operated exceeds 1200 watts or the surge draw of the equipment exceeds 2400 watts.
• Thermal Protection. The RED LED Indicator Light will illuminate and the inverter will automatically turn itself off when the circuit temperature exceeds 150° F

It depends on the appliance wattage and type, IE inductive loads like motors, HVAC compressors etc are harder on it. You didn't mention the 120V btu's but if the unit is running correctly and has no or light other loads on it, it should start it. be aware that it takes about 6 times the current to start the HVAC that it does to run it, so how much other loads are on the generator (base load) is critical

Idle control comes into play when there is no power draw forcing the engine to idle with an electro magent. If you feel that the electro magnet is interfering with governor, temp remove the wire to the solenoid. Usually the idle control will not effect how the engine /gen output power. An overloaded condition will cause the engine the go the full throttle as the internal governor of the engine will try to maintain 3600 rpm. Overloaded condition will greatly shorten the life of the generator/engine. Try to use only about 80 % of rated power. Large motors can draw three times running amps. A compressor using 12 to 18 amps to run can draw over 40 amps to start.
If your generator could handle the load in the past, check the engine for loss of power, or the generator for faulty voltage regulator or capacitors out of range. Easy to check. Connect digital volt meter to plug /load and look at volt reading while running with no load and loaded. Voltage should stay between 110 to 120 under load and with no load (unless goes into idle mode). Good luck

Without knowing the exact model generator you have, it may not even have an automatic voltage regulator (AVR). Colemans were known for losing what is known as "residual magnetism", especially when sitting for long periods of time without use. This residual magnetism is necessary for exciting the field to produce electricity. Here is what you can try: Plug a 110v drill into one of the 110 outlets. While the engine/generator is running, with an open hand (not fingers wrapped around it) spin the chuck while holding the drill trigger in the run position. Many times this small amount of current that will be produced by spinning the drill motor will restore the residual magnetism and excite the field. Keep in mind that if this works, the drill motor will begin to spin immediately since it is plugged into the outlet. Hope this helps.

Voltage is adjusted by raising or lowering the engine speed (governor adjustment), however one must also pay attention to the rpm because your generator was designed to produce 120 volts at 60 cycles while turning 3600 rpm. Your electrician should have tested for htz while testing for voltage. I would recommend re-testing under load and adjust governor to turn 60 cycles to see resulting voltage.

have you tested it loaded or unloaded. try again with big load, not only with lamp or something try paintstripper or other heavy load most easy is a heat generating tool or machine.

It should read 115v-120v with full load. Yes, you can slow the engine down just a little, depending on the engine, there will be a high rpm adjustment. 130v with full speed, no load, is really not too bad.

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

Excite the genset.

with the gen engine running,
1) plug a 3/8 drill into an outlet,
(make sure the drill is set to the forward rotation)
2) hold the trigger in the run position
3) by hand, rotate the drill chuck with a quick flip of your wrist.
*** NOTE: BE PREPARED !!! this will excite the gen-set and the drill will start to run as normal.

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

Your RPM's are too high. There is no voltage regulator in coleman generators (generator is actually made by generac) and is 100% dependent on engine speed. There is a screw under the tank when your looking in from the recoil side. It controls the governor arm. Screw it in and it incresses the rpm, out decrease. Plug something in that draws a decent load while setting the rpms since you want it to put out 120 and 240 underload. Your idle voltage does not matter.

To flash the excitor circuit on a coleman ( the generator is built by generac) you need a 12 volt battery. You quickly apply 12 volts via your 120vac recepticals. NO MORE THAN ONE OR TWO SECONDS! Then check you ac voltage. Most of the time the brushes are burnt up when voltage is low. Check the brushes first. You can access them by taking the end cap off of the generator via two to four screws. The brush holder is easy to spot, two wires leading to the front of the amature. Hope this solves your problem.