I have a really old Lennox unit that ac stopped working I checked the contactor and no 24 vots to outside. Went to the thermostat and I'm only getting 10 volts when testing voltage between red and yellow. I opened my unit and there is no control board. What is sending the unit power ? What should be checked. I really need to fix. That is all that is in unit.
Last edited by PJmax; 07-16-21 at 09:12 AM.
Reason: labeled pic
The transformer is sending control power, that’s located in the photo. Check incoming voltage, and then secondary voltage.
It appears to be hanging from that bracket? And there are wires rubbing on the cabinet knockout. That will cause a short.
A classic repair. The replacement fan center hanging off the old plate.
Instead of changing the center as a unit.... they swapped the new transformer on to the old plate.
The labeling you see in the picture is on your unit. You need to carefully move the wiring in front of it so you can see it. You need to check for 24vAC from R to C.
I wouldn’t buy parts now. Diagnose the issue first. The air conditioner gets control voltage from the furnace.
If you replace the transformer make sure to install some sort of current protection. If you have a short, it will destroy the new transformer immediately without protection.
That is called a fan center. The 24v transformer runs everything and the relay is for the furnace blower.
There are many different versions. They look a little different but all work the same way.
Ok I'm not sure if was already loose but the white low voltage wire that goes to outside contactor is loose in the furnace. There is a red and white wire that runs from fan center to contactor. The red one goes where the thermostat wires are going but the white is not connectedto anything. Does anyone know where the white wire should go
Basic wiring diagram.
R on fan center supplies 24vac TO thermostat.
C on fan center supplies 24v Common TO thermostat and common to outside condenser.
G on thermostat supplies switched 24vac BACK to thermostat for blower.
Y on thermostat supplies switched 24vac BACK to Y terminal for A/C condenser.
W on thermostat supplies switched 24vac BACK to W terminal for Heat.
The Y and W terminals are dead terminals. They don't create any voltage. They are just a splice point.
If you have 24vac to R and C but only 10v at Y. Either something is inline or the thermostat is bad.
The wiring circuit is very simple.
Make sure you don't have an overflow float switch in the R or Y line.
If the red and white are going to the outside condenser...... one wire is on C and the other on Y.
When I see voltage issues with those old consolidated furnaces I usually start with the door switch. The 16 gauge wire connected to the door switch is often melted.
When I see voltage issues with those old consolidated furnaces I usually start with the door switch. The 16 gauge wire connected to the door switch is often melted. -From houston204
YES. Power to switch melted on my unit. Unit is almost 30 yrs old. Replaced control board couple years ago.
In picture you can see
that it melted in the box at the wire nut. Really melted! Why would this happen? Would this indicate that transformer is bad?
Thank you for responding!
So the wire nut was not tight and over time it eventually melted? (That's what I wanted to hear)
Meaning I can just replace wiring and all should be good. Right?
Hi, I do have a stove/range with gas system and would like to replace my old outdoor grill (see pics).
How do I hook up the main tank to it..what kind of gas grill do I need to buy, I am trying to find info with no luck.
I called my gas company (Amerigas) and they were clueless as to how to do it or even if I was legally able to do so. Any ideas? thanks,
[img]https://cimg1.ibsrv.net/gimg/www.doityourselft.com-vbulletin/700x933/gas_tank_da7f4795a56cf48c1eca4b049ef579606bb8c697.jpg[/img]
[img]https://cimg2.ibsrv.net/gimg/www.doityourselft.com-vbulletin/600x800/gas_grill_f0e09efe1080035188319900828d02e2a9c14505.jpg[/img]
for Evcon furnace model DGATO70BDC, serial 940660558 schematics, and wiring diagram. 1995 model Mobilhome gas furnace. MY repairman sends me looking for the above-mentioned schematic and wiring diagrams to print on my PC. The ones on the furnace are no longer readable. He has been in business for 40 years and has worked on my furnace in years past. but needs a readable wiring diagram. I have searched for hours to find the information online. If anyone can help. please let me know. ill attach the pictures I took, maybe it will help
[img]https://cimg5.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1735x1301/furnace_scematics_59cebb410a172e9096db487432fe3d9cee374b82.jpg[/img]
[img]https://cimg7.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1188x891/furnace_wiring_afad619927e8e8d5e5738ef41a806b077bb32f0b.jpg[/img]
[i]this is the one that's really not legible[/i]
[img]https://cimg8.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1700x1275/furnace_d0edcad2a3e4d0a7a2e72c7ef328ac7d08e61979.jpg[/img]
[i]model and serial[/i]
07-16-21, 08:31 AM
