1978 Coleman Presidental

[DinosaurJuice]

Greetings,
I recently bought a 1978 854sqft mobile home. Had a friend check the furnace and we discovered it has a counter clockwise motor (had a clockwise motor in it) and we replaced the fan switch as the fan would not cut in for a long period in the heat cycle.
Now that we have that all done the furnace fan does not cut in on warmup for about 4 minutes into the heat cycle and then half way to tempature the fan cuts out. It heats for a while and then fnally the fan cuts back in. We put in the parts according to the parts list. I am stumped.
Do we need a lower fan switch (its a 100/110 in it)
If I recall the model is an 8690.....
Should I just replace the furnace and be done with it?

[DinosaurJuice]

I'll get the model number for you and the fan switch numbers, etc ASAP - sorry I missed that.

[Robert]

No problem, will need that to know what you should have.



Thanks,
Robert

[DinosaurJuice]

Model: 7680
Series: 856

80,000btu
64,000btu output

[DinosaurJuice]

I'll get the rest today

[DinosaurJuice]

Switch below the transformer:
L15S-2 7680-359
2061L9-718 P3V

Switch above teh transformer:
0934 7710-328
F105-20F 201707 60T82

Transformer:
120V 50 60 C4
BE11246 KIF 45
7660A350
This transformer hums, not sure it that is normal.

Switch at fan:
B3T T.O.T L83 T-O
This one was hard to read and the paper on the back was worn off.

Hope this is all you need sir!
Thank you so much

[Robert]

Make sure the burner tube and burner orifice/spud behind the gas valve are all clean and clear.

Spiders like to build webs in the orifice/spud.


Then if it is still cutting on/off, test across the limit switch to see if it is opening/closing with each off/on sequence.



Thanks,
Robert

[DinosaurJuice]

OK. Will check the above.
The transformer humming is normal?
Thank you Robert.

[DinosaurJuice]

Actually if you can link waht I need to buy - I'll replace all the switches.
Even teh transformer as well.

[DinosaurJuice]

Well I want to repalce the old tired furnace with a new unit - I am looking at a Miller M1MB070ABW A/C Ready. Its a tuch smaller at 70,000 BTU compared to the 1978 Coleman Presidental I have now. I take it would be enough to heat the place? (Sealed cieling tile joints, New windows, doors, etc... but not re-insulated)

[DinosaurJuice]

so waht I am saying is I want to keep the old one running well until I get a new one installed! LOL

[Robert]

Hi,

You're very welcome. No, transformer humming is usually a sign it is heading out. Some hum longer than others, but I always recommend replacing when it starts to hum.

Make sure all connections are tight and clean and you have correct voltage (120vac primary-line/24vac secondary-load). If so, it should not hum. Keep it though, could be used in an emergency sometime.



Thanks,
Robert

[Robert]

LOL, you kept posting while I was answering, be right back with ordering info.


Thanks,
Robert

[DinosaurJuice]

Ah sorry must be the black tea I am drinking! LOL

[DinosaurJuice]

BTW - I redid the connections when I bought the place - they needed a redo.