[gabebcarlson]

Hello, I have a OLD Siegler Holly V70 forced air gas furnace with a General Controls gas relay, and trying to rewire it so that 1 the auto fan limit works right. And 2 make it so that I can turn on just the fan with the thermostat.

I believe this is just a 2 wire system because when I started by replacing the thermostat to a digital one with a nonswitch fan control, the wires to the old t-stat were 2 black wires.
So I pulled some new 18/5 to the furnace.

This furnace has I said a fan limit which worked only if I pulled the knob to manual. I would not turn on in auto. As well the furnace has a switch on the outside to turn on the blower which is what I used to push out the heat sense the auto did not work.

Now here is my big problem I foolishly disconnected all the wires so that I could hook up the new thermostat. Not knowing that normally the wires are not just black Im stuck. ALL the wires besides the 2 from the transformer are black ( and the new wires I just pulled) to make matters worse the gas relay is marked as such.
There are 4 screws in a row from top to bottom facing the gas relay . Above the first two screws is written 24v and above the next two is written Thermo. Now I unscrewed the cap off and only the top screw and the bottom screws have any thing connected to them.

So as a quick recap. Off the transformer there is a red and white wire leading to the gas relay, a switch that connects to the outside furnace, 2wires going to the fan limit both are black and wires going to the blower. From the fan limit 2 black wires load/line heading to the gas relay. And the 18/5 wires from the thermostat to the furnace/ gas relay area.

I hope I detailed this out well enough I have not been able to find a wire diagram for this furnace so I hope you can help.
Thank you

[labman]

See https://www.askmehelpdesk.com/heatin...tml#post750342

I hope a mod responds to my request to merge these.

[gabebcarlson]

Update,
Here are some pictures of the furnace. As well due to my ignorance any where that I put Gas relay I learned is a Gas Valve sorry if that made things confusing. :rolleyes:

[labman]

I wish the mods would merge this with the thread I posted your email to, https://www.askmehelpdesk.com/heatin...tml#post750342

There may be people here that know the wiring diagram for your gas valve and the limit switch, but I don't.

To get heat, you need two low voltage circuits. I think both may pass through the limit switch with the 4 wires. Starting at the transformer, power flows to R or RH at the thermostat and then back from W when it is calling for heat. That should work with the red and white wires connected to the 2 lower terminals labeled thermo. Power then flows to the high limit section of the limit switch and back to the gas valve unless it overheats and opens. It then flows through the coil of the gas valve and back to the transformer. You want to connect the 2 terminals of the transformer to the 2 terminals labeled 24 volts. 2 leads of the limit switch should be connected when the furnace is cool. You want them connected to 2 wires from the gas valve to open the gas valve and get the burner on.

The second circuit power flows from the transformer to the 2 leads of the limit switch that aren't connected when cool. After the burners come on, the contacts close, and power flows from the last lead to the coil of the fan relay and back to the transformer.

I don't see anything in your pictures that looks like a fan relay to me. It could be in the box with the transformer. It should have 4 terminals line connected to the black wire from the house, load connected to the blower, and 2 coil terminals, one connected to the limit switch and the other to the transformer. The other lead of the blower should connect to the white wire from the house.