Coleman/Mach A/C Issue

[samalf23]

2018 Alante 31v - had front a/c on and was working fine when we went out for the day - came back a/c was no longer working - only hooked to shore line no other source of power - breakers not tripped but reset, same results - rear a/c working fine. Thinking it can be starter caps or bad board, any other suggestions?

Will get up on roof when we return from our travels and it is parked in driveway at home.


TIA
Sal

[JimD]

By not working do you mean it won't turn on? If that is the case and it is controlled by a wall thermostat, your problem could be there.

1. Is the thermostat displaying a temp? If not then it may not be receiving 12 volts (blown fuse at panel), could be bad, have a blown internal fuse, etc. If it also controls heat does that function work?

2. Will the fan turn on if fan setting changed from auto? If the fan runs by itself then there could be a problem with the compressor, the 12 volt signal from the thermostat to the compressor control circuit, start capacitor.

Just some thoughts off the top of my head. The wall thermostat just sends 12 volts separately to the compressor control and the fan control. If the thermostat is bad you can try jumping the 12 volt line to the thermostat to the control line for the compressor or fan. 2 different output wires.

[samalf23]

Originally Posted by JimD

By not working do you mean it won't turn on? If that is the case and it is controlled by a wall thermostat, your problem could be there.

1. Is the thermostat displaying a temp? If not then it may not be receiving 12 volts (blown fuse at panel), could be bad, have a blown internal fuse, etc. If it also controls heat does that function work?

2. Will the fan turn on if fan setting changed from auto? If the fan runs by itself then there could be a problem with the compressor, the 12 volt signal from the thermostat to the compressor control circuit, start capacitor.

Just some thoughts off the top of my head. The wall thermostat just sends 12 volts separately to the compressor control and the fan control. If the thermostat is bad you can try jumping the 12 volt line to the thermostat to the control line for the compressor or fan. 2 different output wires.

Thermostat is the original does not display temp - checked to see if thermostat was getting voltage and it is. But fan will not run so not sure at this point if it is the Run or Fan Cap or the control box or all three. I have parts breakdown but no manufacturer troubleshooting steps/guide. The caps are relatively inexpensive but not going to get both if not necessary.

[JimD]

Originally Posted by samalf23

Thermostat is the original does not display temp - checked to see if thermostat was getting voltage and it is. But fan will not run so not sure at this point if it is the Run or Fan Cap or the control box or all three. I have parts breakdown but no manufacturer troubleshooting steps/guide. The caps are relatively inexpensive but not going to get both if not necessary.

12 volts to the thermostat is a good start. For it to fire up the AC, it will send 12 volts to the compressor line and 12 volts to the fan line. Since you measured 12 volts coming into the thermostat you could measure it going out on the control lines.

The AC motors are 2 separate units and probably have their own start caps. 120 volts is required for either to run. If neither will start I would look for something in common with both - 120 volts and thermostat signal to them.

You may need to measure voltage inside the AC to make sure you have the 120 volts getting there and also the 12 volt "turn on" signal. If you can get the model of AC you may be able to get the manual from the manufacturer's web site. It should show the wire connections and may even have a troubleshooting section.

My son has an AC unit in his 5th wheel that had an old analog thermostat. I bought him a nice digital one and went to install and found out it operated on 7 volts instead of 12. Not sure what system you have but if you measure 12 volts at the thermostat it is the newer style, at least compared to his olf one.

If you look at the control board inside the AC, which you may be able to see after removing the bottom grill (if you are lucky), look for any wires that may have come loose.

[samalf23]

Originally Posted by JimD

12 volts to the thermostat is a good start. For it to fire up the AC, it will send 12 volts to the compressor line and 12 volts to the fan line. Since you measured 12 volts coming into the thermostat you could measure it going out on the control lines.

The AC motors are 2 separate units and probably have their own start caps. 120 volts is required for either to run. If neither will start I would look for something in common with both - 120 volts and thermostat signal to them.

You may need to measure voltage inside the AC to make sure you have the 120 volts getting there and also the 12 volt "turn on" signal. If you can get the model of AC you may be able to get the manual from the manufacturer's web site. It should show the wire connections and may even have a troubleshooting section.

My son has an AC unit in his 5th wheel that had an old analog thermostat. I bought him a nice digital one and went to install and found out it operated on 7 volts instead of 12. Not sure what system you have but if you measure 12 volts at the thermostat it is the newer style, at least compared to his olf one.

If you look at the control board inside the AC, which you may be able to see after removing the bottom grill (if you are lucky), look for any wires that may have come loose.

So I looked at the control board and see that one of the wires has come off its connector - have to check the other A/C to see what connector that wires goes to (wish I can post a pic of it cause it is clear as day)

[samalf23]

Originally Posted by samalf23

Thermostat is the original does not display temp - checked to see if thermostat was getting voltage and it is. But fan will not run so not sure at this point if it is the Run or Fan Cap or the control box or all three. I have parts breakdown but no manufacturer troubleshooting steps/guide. The caps are relatively inexpensive but not going to get both if not necessary.

Checked wiring box and fan control connection came loose. Crimped on new connector and a/c is back up and running.

[Foretm]

Glad to hear you're back up and running.