The system was running great then suddenly it stopped and the digital thermostat went blank - according to my roomate who was home at the time.
I have a Carrier 58STA070 that is blowing the 3amp fuse on the furnace control board. I have a non-programable Totaline thermostat controlling the furnace.
Here is what I have done...
I turned off the breakers to the unit. Replaced the blown 3amp fuse, replaced the blower cover, turned ON the breakers, went back to the unit and saw that the red light on the furnace board was illuminated solid,but turned off after about a minute. I then went to the themostat that was now ON. The thermostat had retained my Cool set tempature and was attempting to turn ON the unit "cool ON" was flashing. The unit never came ON. I then pressed the "fan" button , immediatly after pressing the fan button the thermostat went blank. I opened up the furnace and the 3amp fuse on the furnace board had blown. I went through the same motions again and the 3amp fuse on the furnace control board blew again.
Is my thermostat bad... I have checked for loose/touching wires between the thermostat and furnace and all are good.
[Edited by eisenberg on 08-04-2005 at 02:48 PM]
You have a low voltage short. I would say in the stat wire.
unless you did something to the thermostat to destroy it , it isnt bad.
have you considered calling someone out to look at it that is familiar with hvac equipment.
You could always take the fuse out of the thermostat and put a paper clip where the fuse goes and turn the unit on
whereever the smoke comes out of ....thats where you will find the problem
per your post I retraced the wire and found the trouble. The installed had used the U-shaped nails to hold the stat wire in place. Instead of allowing the stat wire to move freely within the U-shaped nail they had mashed it down....took about 6 months to wear through the insulation until copper met nail.
thanks again...the family is cool again in Richmond where it has been 95+ w/ 100% humidity everyday