Lennox G12 Blower Runs Constantly

[chronicnetpro]

Hi, all.
I have previously paid a service tech to fix this problem. Long story short, too much time has elapsed to try to get the company to make good on the repair, so I am trying to troubleshoot it myself.

I have replaced the fan limit switch, no difference. The diagram on inside of furnace door DOES NOT show a fan relay, so I don't know if there's supposed to be one or not.

Inspecting the furnace junction box shows that someone has done some rewiring on this (wire caps are a mix of different colors/sizes from stock). If they have hard-wired this for constant fan operation, or if they have wired around the fan relay (if there's supposed to be one)I am sunk until I get more wiring info.

I tried to buy a manual from Lennox, but they won't sell to the public. If some kind soul could shed some light on this problem, it would be much appreciated. Thanks,
Steve

[heatmon]

Can you be more specific on the choice of fan & limit switch which you replaced yourself? Did you replace with a cam-stat (original equipment) or the honeywell recommended about 20 years ago, as this furnace could be almost 40 years old. Late 60's to early 70's as I remember. You didn't state the exact problem you're having, and your furnace never did have a fan relay, unless it's handling air conditioning in the summer. If so, what happens when you turn on the fan switch at the thermostat?

This is just my opinion, and with it and a dollar, you can get a cup of coffee in most places.