intertherm MAC 2460 troubleshooting

[mooseye]

I have the above electric furnace and I need some help troubleshooting it.
I was able to make the unit work by jumpering a couple of the wires. I know this is not safe but so was freezing and I didn't leave it unattended. I have a meter and I have 240 volts to and out of breakers and to most of the wires on most of the components in the control panel. I need to know how and in what order to check the individual parts such as limits and sequencers.
I have 29v from the transformer. There are four sequencers mounted on a metal assembly that seems to have a heating element in it. I kind of suspect that this element is not heating up. I assume that the sequencers will not work till a temp is reached by this element. Is that correct and could it be bypassed or is there a replacement available?

[Robert]

Hi,

The bottom terminals of the sequencers are the heating coils and need 24vac across them usually (could be higher coil voltage needed sometimes).


Then you need 120vac into top and middle terminals, when heater coils close the middle and top contacts, then 120vac out of them to the left side terminals of the heating elements.

Then, you have 120vac from breakers, through the limits to the right side terminals of heating elements.

If you measure across the elements, you get 240vac and if you measure across the sequencer terminals (top and/or middle), you have 240vac IF contacts are open and 0vac when closed.

120vac from each side of sequencer to ground.

ONE of the sequencers will also control the blower motor.


Hope this helps.

Thanks,
Robert

[mooseye]

First off, thanks for taking the time to reply.
I think this unit may be somewhat different to what you described. There are four stage switches, as they are referred to in the wiring diagram . They are mounted on a metal assembly with a heat strip inside. There are only two terminals per switch and I suspect that they are heat activated as a safety. This heat strip is broken and I was wondering if it could be bypassed, and if not, where can I find a replacement?
This unit is original in a 1970's era mobile home and it will work if I jump the stage switches, just not automatically.
Here is a photo of part I am describing:

[Robert]

Hi,

You're very welcome, happy to help. The heater coils will bring the elements on in a timed sequence, so shouldn't bypass them.

I would get an hvac tech out and you should be able to change it to a sequencer type set up with some experienced help.


Parts are no longer available for the furnace, so it would have to be upgraded to a newer set-up if possible. If not, would be time to replace the furnace.


Thanks,
Robert
www.mobilehomerepair.com