Need Info or Manual To Troubleshoot Older Coleman AC/Furnace

[Mandeville]

Hello, your site looks like just the thing for depressing heaters. Hope you can sell me a part.

I am trying to figure out what is wrong with my Coleman Furnace in the typical Manufactured Home style cabinet. It is part of a combined AC & Heater unit. The unit is circa 1984.

Cooler/Blower unit works wells. Responds appropriately to thermostat. A new blower was installed a couple of years ago and the capaciters for both the air conditioner and blower were replaced about a year ago. This is thunderstorm country and I think that the lightning transients finally did them in, plus old age and a lot of use here in Arizona.

Heater does not work, no response to thermostat settings, blower will not turn on when set to AUTO.

Blower can be manually turned on at thermostat but no heat is provided.

I have removed the panels and am trying to figure out how to troubleshoot. One furnace man told me over the phone that it was probably the "sequencer". He had me come to his shop and tried to sell me a part but it did not look like the sequencer in the unit. Not knowing about these parts, I declined.

Is there a manual of operation - laying out the principles of operation and control - available for these type of heaters? This might help me troubleshoot the unit to determine absolutely that the problem is that I need a new sequencer. I am looking specifically for something which lays out the behaviors and signals I can monitor electrically to see what is going on. I have no problem working safely on high energy circuits, I used to be a radar technician. I just don't know a thing about these types of AC units.

I DO NOT NEED WIRING DIAGRAMS.....have the original set which came with this manufactured house.

Specs for the system:


Air Conditioner Cooler/Heater

Coleman Central Electric Furnace
Serial 108473080
Model 3400-818

240 VAC/60/1
16.92 KW / 70.5 Amps

Heating Coil Assembly
w/3 limit switches 3400-336

Sequencer - mounts separately
apparently part number is 3400-357 (read from the part mounting plate)


Michael Mandeville
623-374-9585
mwman@earthlink.net

[Robert]

Hi,


There is no manual of operation like you are inquiring about.

The wiring diagram shows the layout of the circuits which can be tested for proper voltage.


Go here and scroll down right side:

Sequencer # 3115-3571

Click on pic for enlarged view.


The sequencer controls heating elements and blower motor in heating/auto mode.

A blower relay controls blower motor in Fan ON and in cool/auto modes.


IF power is reaching the sequencer, most likely the sequencer is bad.


Set t-stat to Heat/Auto/85*.


Bottom brass terminals H1/H2 should read 24-28VAC across them.


Top silver terminals M1/M2 should read 0VAC.


IF it reads 240VAC while H1/H2 reads 24-28VAC, sequencer is bad.


IF you get 24-28VAC at H1/H2 and 0VAC at M1/M2, then test/check the limits and heating elements.


If the sequencer is needed, it can be ordered at above link through PayPal.




Thanks,
Robert

[Mandeville]

Hello Robert,

thanks for the speedy response. It took me a few days to get back to you because I remembered my AC meter was burned out long ago and I had to find another one. I checked all power delivery through the fuses, limiters, and heating elements to the sequencer. All show same presence of power

After turning on the thermostat as you suggested, I measured the sequencer terminals and obtained the following responses:

H1-H2 zip zilch and nada

M1-M2 240 volts.

This is different than the two options you spelled out so I am not entirely sure.

Is this the sequecner or could it be something to do with the thermostat connection and operation?

Let me know and I will order what parts I need. Do I order the same sequencer as the pix you sent me....3115-3571? Looks pretty much like the one I have, though the number is different.

Thanks again for your service.

[Robert]

Hi,


IF you had t-stat set to Heat/Auto/85* and read 0VAC at H1/H2, then you are not getting 24vac to sequencer.


Go to transformer and test for 24-28VAC across the LOAD/SECONDARY side terminals.


If there, then go to t-stat and test with t-stat turned off.

Test across RH and W for 24-28vac.


IF you have it, turn t-stat back to heat/Auto/85* and see if it now reads 0vac across RH and W.



Gotta have 24vac low voltage for sequencer to work.



Thanks,
Robert