[Fatt]

White Rodgers type 1F86-344 showing high 80s to 90s on set temp. I pulled batteries and replaced. Now shows 65 actual set temp 88. Looking in furnace decided to check vacuum tube on fan and see it is plugged with what appears to be calcium. Drilled it out gently into fan housing and now it sucks ok but I didn't break through completely. Should I push drill until it breaks completely into fan chamber?


Should I buy new Tstat or can I replace with old mechanical type?
Furnace is Heil 80%. I'll look for model...




Thanks in advance,
Fatt

 

[roughneck]

It appears you have two completely different problems. The pressure switch port needs to be completely unobstructed.
As for the thermostat make sure there’s no air leakage around the wire penetration in the wall.

 

[Fatt]

It appears you have two completely different problems. The pressure switch port needs to be completely unobstructed.
As for the thermostat make sure there’s no air leakage around the wire penetration in the wall.

Thanks Roughneck, that's correct. So, will an old mechanical Tstat (4 wire) work in a Heil 80% efficient furnace/ac setup?

 

[roughneck]

Either mechanical or electronic. Basic nuts and bolts operation is the same, your just closing circuits.

 

[user_12345a]

You don't change the stat to figure out if it's the problem, you bypass it or set it to call for heat and see if there's power being applied with a meter.

 

[roughneck]

I’m getting a little confused here.
Is the thermostat showing the correct room temperature? Is it operating properly since you replaced the batteries?

 

[Fatt]

Roughneck asked: I’m getting a little confused here.
Is the thermostat showing the correct room temperature? Is it operating properly since you replaced the batteries?[/QUOTE]


Tstat is obviously bad. Once I fixed the vacuum tube it would start the furnace after applying the 120v power to the furnace. But then when I went back upstairs the "target temp" would automatically rise about one degree every five seconds. I watched it rise to 136 degrees. Had to shut it off before it got that hot! (joke)



Thanks for your help.

 

[roughneck]

So what issue was the furnace having? Was the pressure switch not closing?
As I said before it sounds like 2 separate issues your having.
The pressure switch tubing should never get so bad it seals shut.
When was the last time the furnace saw any maintenance?
Are you certain there’s not an air leak behind the thermostat?

 

[Fatt]

So what issue was the furnace having? Was the pressure switch not closing?
As I said before it sounds like 2 separate issues your having.
The pressure switch tubing should never get so bad it seals shut.
When was the last time the furnace saw any maintenance?
Are you certain there’s not an air leak behind the thermostat?

Yes, I agreed there are two issues. The pressure switch tube to fan connection is now clean. Where the white crumbs come from I have no idea. Surely they aren't coming out of the diaphram switch? I cleaned that tube a year ago and it was packed hard with white powder. I'm gonna switch out the stat today and put in an old mechanical. I don't think there is anything coming out of the wall that is at 136 degrees. Why are you concerned about a air leak to the basement? There are dozens in this house. At any rate, if there is a hole in the wall I'll tape it up. :wink2: