Coleman Furnace (#7700B)

[Robert]

Hi,

One is for heat and other is for a/c.


OR, sometimes the heat transformer will be disconnected and the a/c transformer used for both IF it is high enough VA rating.


Test first to see if good or bad.




Thanks,
Robert

[SebasC]

Heat transformer is connected too I see. Followed the lines. I'll replace it either way, I don't think it can hurt too much I would assume. But I mean neither AC or Heat works

[Robert]

That's why you need to test them both to see if they are getting primary voltage.



Thanks,
Robert

[SebasC]

Okay, I Think (hopefully) this is my final question (prob not) When testing the transformer I assume (duh) I would have to have the lines hooked up.

[Robert]

No wires, no power to test.


Yes, connect the wires and test for 120VAC primary voltage to the primary-line side of the transformers.


You MUST have that in order to have the 24VAC on the secondary-load side.


Thanks,
Robert

[SebasC]

Alright so put the read part of the multimeter on the incoming (120V) and the black one on any part of the metal of the furnace?

[Robert]

Red on one teminal and black to side of metal control box where transformer is located.


Do this to both terminals.
One should read 120vac and the other 0vac.

Then place red on the one that read 120vac and black on the other one.


Should read 120vac if ok.


Go to other side and do same, but should read 24vac on that side.



Thanks,
Robert

[SebasC]

Nope no voltage on either one of the transformers.. argh I dont have the money for a repair man either and its getting hot.

[Robert]

IF there is zero voltage coming to primary-line side of both transformers, then the breakers and/or fuses need to be checked.


That would need to be done by a hvac tech or a friend or relative with electrical experience.


Thanks,
Robert

[SebasC]

Fuses I Can Not seem to find... unless there are some inside the unit itself?

Breakers? You mean in the main control box?

There is no specific point to which i hook up the 120VAC to the Line side of the transformer right and 24VAC to any part of the load side.

As long as 120VAC goes to Line and 24VAC goes to load I should be fine?

Is there any way to test a transformer without having it hooked up? Just to see if there is continuity?

[Robert]

Hi,


It should have been marked or the location marked down before removing the wires.

Test the two wires, one lead to each for 120vac.


You can ohm across it, but testing for voltage is cut and dried.


If you do not have the 120vac voltage to it, then it will not work at all.


It is time to call an hvac tech or get a friend or relative with electrical experience to continue this.


With the very limited experience you have, it is just too dangerous to continue attempting a DIY repair here.


Take care and best wishes,
Robert

[SebasC]

Well I Know which lines are 120VAC and which lines are 24VAC what i meant is when you look at the line side it doesn't matter which way you hook up the 120VAC lines right?

I know which lines are which I was just wondering if it mattered how you hook up your line (120) and load (24)

Also I Am looking for something to replace the Furnace Control box On/Off Switch with Model Number: 7660-3511 (Carling MAAOA-BL)

[Robert]

I understood what you meant and yes, it does matter.


I will look up the switch shortly.



Thanks,
Robert

[SebasC]

Damn, alright because my transformer does not say on it anything special other than line and load... Pretty plain.

If i get OHMs across both load and line does that mean the transformer is in tact and usable? because on both transformers (Old & New) my analog multimeter went all the way to the right when testing (0 Ohms)

[SebasC]

Okay so i have two transformers.

One is a Lennox 42J32 - 120V: Pri 24V:Sec 40VA - 0 Ohms across both terminals (New Transformer)

The other one is like the 2940A3541 on your parts page 120V: Pri 24: Sec - 0 Ohms across both terminals (AC Box Transformer)

I reconnected outside wires with Wire Nut (Tightly)

Hooked up transformers.

Can not find Circuit Board or Fuses (Inside Coleman Furnace 7700B)

I have circuit breakers inside my electrical box (Can there be fuses in there too?)

I can not seem to register either 120V or 24V.

Could be the fact when i tried my multimeter on the switch i had a big spark.

I accidentaly put the red and black lead of my multimeter on one and the same hook up of the switch (On/Off Switch on Furnace box). (Could have shorted something for sure)

So I Know I have to get an electrician but is there any idea where they could look? Electrical box would be the most obvious place because i had a big spark while checking the on/off switch and it sparked on me and burned a lead (Black one)

Could i have blown a relay too by any chance, is there any way to check if they are actually working or able to provide power?