Back in October I got a new Coleman-Mach 48008-9660 3 P. S. heat pump and a 9630-715 non-ducted ceiling assembly.With warmer weather, I've noticed a problem with the air conditioning. On LOW COOL or HIGH COOL, with the temperature knob in an intermediate position between coldest and warmest, after a few minutes of operation, the fan noise suddenly decreases markedly, and the voltage drops to roughly 106 volts. After 2-3 seconds, the fan noise and the voltage return to normal. However, when on the genset or at an RV park with marginal voltage, the voltage drops so low that my surge protector disconnects, turning off all AC electricity in the RV.When first turned on, air conditioning starts normally, with only a slight voltage drop. There's never a problem if the temperature knob is at the coldest setting. There's never a problem on HIGH HEAT (heat pump). The RV has 30 amp service. There's no wall thermostat; all controls are in the ceiling assembly.I could be totally wrong, but it seems like the compressor stops and then restarts after 2-3 seconds.Does anyone else have this problem?Airxcel just says take it to a service center, and I guess I will.BTW, the heat pump works well, though I wish it had a LOW HEAT setting; the fan is noisy on high.

Voltage drops can be solved with an autoformer.

Is that 106 volts to the air conditioner or the whole trailer? If you have one, put an amp clamp meter around the air conditioner hot wire and see what the current is doing during the voltage drop. If you don’t have one, you can buy one relatively inexpensively at Home Depot, Lowes, or even Harbor Freight. You don’t need a high dollar meter for that.

It sounds like your compressor is trying to re-start too soon.After they have shut off, most compressors need some time for the refrigerant pressure to subside on the high-pressure side of the evaporator coils.If too much of this pressure remains when the compressor attempts to start again, it makes the compressor work much harder while starting - or may even prevent it from starting.While it's attempting to start against too much pressure, the compressor draws an excessive amount of current. If it fails to start, it will continue drawing a lot of current for a few seconds, until the overload protector opens the circuit supplying power to it.During those periods with it is drawing excessive current, the voltage being supplied to the RV tends to drop - which makes the lights dim and the fan slow down.One way to increase the amount of time between compressor shut-off and re-start is to add some "thermal mass" to the temperature sensor. The extra mass requires more time to change temperature - which slows down the speed at which the sensor responds. So, you get longer delays between compressor shut-down and re-start.Why my old Coleman had this problem, I installed a big wad of tinfoil over the temperature sensor, held in place with zip-ties.It sounds hinky, but it works. :B

What you are hearing is the compressor start... For some reason (Too far from the park's distribution panel?) the current draw is enough to suck down the voltage.A "Soft start" or "Hard Start" kit (Really the same product depends on who is talking) might help.

wa8yxm wrote:.....A "Soft start" or "Hard Start" kit (Really the same product depends on who is talking) might help.Not really. Work in different ways.https://www.softstartrv.com/difference-between-hard-start-and-soft-start/

Coleman-Mach 48008-966 AC large voltage drop | Good Sam Community

BB_TX
Nomad
May 25, 2022
wa8yxm wrote:
.....
A "Soft start" or "Hard Start" kit (Really the same product depends on who is talking) might help.

Not really. Work in different ways.

https://www.softstartrv.com/difference-between-hard-start-and-soft-start/
wa8yxm
Explorer III
May 25, 2022
What you are hearing is the compressor start... For some reason (Too far from the park's distribution panel?) the current draw is enough to suck down the voltage.

A "Soft start" or "Hard Start" kit (Really the same product depends on who is talking) might help.
Skibane
Explorer II
May 25, 2022
It sounds like your compressor is trying to re-start too soon.

After they have shut off, most compressors need some time for the refrigerant pressure to subside on the high-pressure side of the evaporator coils.

If too much of this pressure remains when the compressor attempts to start again, it makes the compressor work much harder while starting - or may even prevent it from starting.

While it's attempting to start against too much pressure, the compressor draws an excessive amount of current. If it fails to start, it will continue drawing a lot of current for a few seconds, until the overload protector opens the circuit supplying power to it.

During those periods with it is drawing excessive current, the voltage being supplied to the RV tends to drop - which makes the lights dim and the fan slow down.

One way to increase the amount of time between compressor shut-off and re-start is to add some "thermal mass" to the temperature sensor. The extra mass requires more time to change temperature - which slows down the speed at which the sensor responds. So, you get longer delays between compressor shut-down and re-start.

Why my old Coleman had this problem, I installed a big wad of tinfoil over the temperature sensor, held in place with zip-ties.

It sounds hinky, but it works. :B
BB_TX
Nomad
May 25, 2022
Is that 106 volts to the air conditioner or the whole trailer? If you have one, put an amp clamp meter around the air conditioner hot wire and see what the current is doing during the voltage drop. If you don’t have one, you can buy one relatively inexpensively at Home Depot, Lowes, or even Harbor Freight. You don’t need a high dollar meter for that.
Lwiddis
Explorer II
May 24, 2022
Voltage drops can be solved with an autoformer.

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Coleman-Mach 48008-966 AC large voltage drop

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