Cat 259b3 no air conditioner power

[Inland1]

I have a 259b3 with a/c but, now have no power to unit. Fuse in fuse box is good. Tested relays and all have same ohms about 91. The only place i seem to have disconnect in voltage is at the fan switch. I can jump the switch and get the fan to work but, no light on main on/off switch. Does that switch, back feed in to the main switch and, needs to be connected? All I can figure is i may have a bad fan switch but, not sure if that will shut down entire system or if there is another issue and the switch is just a side effect. Thanks for any help.

 

[Nige]

Is your machine a YYZ-prefix model ..?
I'm sure an Electrical Schematic would help you but there is a Serial Number break in the YYZ product. Need to know if your machine S/N is above or below YYZ01542.

 

[Inland1]

Yyz 05082 thanks

 

[heymccall]

pole #2 on switch controls everything. If it's not outputting 12v when in any position but off, then the switch is bad.

 

[Nige]

Here's the schematic. It also contains come machine views that might be useful.

 

[Inland1]

Thanks for the schematics guys, I will see what I can learn tomorrow.

 

[Inland1]

Is the black line coming out of connector 14 on Nige's schematic suppose to have any votage?

 

[Inland1]

Also wondering about voltage through black/white on connector 15. Thanks fot any help.

 

[heymccall]

Is the black line coming out of connector 14 on Nige's schematic suppose to have any votage?

No, that is earth ground.

Also wondering about voltage through black/white on connector 15. Thanks fot any help.

That one is ground when the pressure switch is closed.

 

[Inland1]

Heymccall, thanks for the info. I am currently stuck at the condensor fan relay. I have 12.4v on the red but, nothing coming out of any the others. Swapped relays and the same. Am i suppose to have power coming out? I would think so but, both relays had same result. Thanks

 

[Nige]

You won't have power on the condenser fan relay until it pulls in IMO.
Should be 12V between the Red (blue color on schematic) wire and ground (pin 30).
The black wire on pin 85 should have a good ground.
The condenser fan relay pulls in when the BK/Wh wire on pin 86 is energized. The power for that wire involves the thermostat, the compressor relay, and the system pressure switch. Maybe the pressure switch might be a good point to start. You should have continuity between Pins A & B on the switch connector.

It might be a bit late to be asking this but has anyone had a set of A/C gauges on this system to check if it actually has any refrigerant inside it..?

 

[heymccall]

I read that different, Nige.
With blower on Low or High, and AC On, the condenser fan relay should latch, resulting in the condenser fan running.

 

[Nige]

You're right. I was looking at the other side of the circuit.
Reading back right from the OP, I'm still not clear just exactly what is or isn't working ........

The only way I could see to chase this logically is to follow the power. All wires marked blue on the schematic have system voltage when the key switch is on, so with the key switch on.....
1. Is there power on the two red wires from Pin 87 of the key switch relay that feed the switches for the blower motor and the A/C On/Off..?
2. When the blower motor switch is set to either low or high does the motor run and is there power in the green wire from the BM switch to Pin 3 of the A/C switch..?

 

[Inland1]

1. Is there power on the two red wires from Pin 87 of the key switch relay that feed the switches for the blower motor and the A/C On/Off..?
2. When the blower motor switch is set to either low or high does the motor run and is there power in the green wire from the BM switch to Pin 3 of the A/C switch..?

1. Power on red wire
2. No power on green wire coming from BM to on/off switch

I'll replace blower switch and go from there. Hopefully, fixes problem. Thanks

 

[Nige]

So if there is no power on the green wire I would guess that the blower fan doesn’t run either, correct..?

 

[Inland1]

So if there is no power on the green wire I would guess that the blower fan doesn’t run either, correct..?

Correct. No power to fan. I can jump the red to orange on fan switch and get fan to run but, not when switch is connected. Can i jump the red to green and jump the switch, to verify switch or, is that a problem. Thanks.

 

[Nige]

I'm pretty sure you can. If you jumper the red coming into the fan switch to the green going out, then put the A/C switch into the "ON" position it should pull in both the condenser fan relay and (provided the thermostat is closed) the compressor relay. It might pay you to disconnect CONN 15 while you are doing this, because then you won't be either starting the fans of pulling current through the A/C clutch.

 

[Inland1]

Ok, I jumped the switch and main switch came on and condensorr fan turns on. Compressor does not engag, motor running. Should it? Thamks for the help, greatly appreciated.

 

[Nige]

You may have another issue but first I suggest to replace the switch. The Part Number for your machine is 236-5067.
Get the switch working correctly before moving further with diagnosis would be my thoughts.

 

[Nige]

The switch isn't going to break the bank. Somewhere around $40. Get a new one installed and go from there.