Blower constant, temp staying at 64-66

My heater fan is blowing constant, and it is cool air. It is a gas furnace. I upped the temp to 74 and it only keeps the house at the 64-66 degrees. The temp on the stat is reading correctly, so I don't think that is what it is. Just started doing this yesterday morning and the heater fan has run ever since, I am assuming because the stat is saying it is only 66 and I have it set to be 74, so it thinks the furnace has not warmed the house to the set temp. Sorry if this makes little since, but hopefully someone can figure out my ramblings and give me suggestions. I know we are not out of gas b/c for one, it must be a little heat coming into the house to keep it in the 60's, since it was in it's 40s today and also we have hot water still, and that is gas heated.

It is a trane sv90 unit. If I turn the red gas switch off there is a blinking red light on the unit that goes off. When I turn it back on, I can see a red light as well as a green light there, then it goes to blinking red again, and it blinks 4 times, then pauses then repeats. I have checked the breaker box, everything is on. I don't know if this helps any!

 

Solenita...
I hope you meant "XV90" b/c Trane does not have any SV90 units. Perhaps your furnace looks like the one below. Please confirm.

If so, the sequence of 4 pulses, pause, 4 more pulses, etc., (on that red light) means that a control inside the furnace called the "Limit Switch" has turned the flame OFF for safety reasons. As an additional safety measure, another control in the furnace, called the board, turns the house blower ON, which is why you feel that cold air coming off the registers.

If we are lucky, the reason for this problem is a dirty air-filter. When was the last time you replaced your filter? Please remove the existing one and put a new one in place.

Prior to replacing the filter, first turn the red gas switch to OFF, and then proceed to replace the filter.

 

The unit is the xv90, sorry for the typo. The filter on the downstairs intake is one that can be washed. I did that last night. I replaced it, but I did not turn the gas off first. Are you talking about that one? Is there one inside the unit as well? Sorry, dh normally takes care of this, and he is deployed. The upstairs intake is a regular one and it was just replaced last month. Maybe the furnace needs to be cleaned?

Okay, did a bit of research myself, I can't find a darn access that would have a filter in it. I took panel doors off, nothing there. My register is up high at the ceiling, and that one is the one I washed out. I can't find anything else. Maybe in cleaning the one, I just need to reset it somehow, now?

I remember when the guy came and cleaned it before, his hands got quite dirty in cleaning it, and that came from inside the closet the unit is housed in. I was too busy trying to keep the kids back to watch what he was doing. Now I am kicking myself for not standing over him!

 

some pics showing the things you're mentioning will be quite helpful.

Hopefully the washing of the filter is all that was needed. But you do need to reset the furnace. Flip the red gas swith OFF for about a minute before turning it back ON. At the same time, turn the thermostat switch to OFF.

The system should reset after you turn both back ON

 

My unit looks just like the one pictured. The panels I took off, popped right off. Both on the front.


I just hit the gas switch (the one on the wall like a light switch) and left it off for over a minute. Turned it back on, the light flashed red in a steady blink. Turned the stat back on, the blower turned on and it started flashing the pattern of 4's again.

 

The 4 flashes mean that a limit switch has tripped.

Your unit has two limit switches, maybe more if it is a downflow unit; and at least one of them can be reset manually (the other should do so automatically, else is defective)...It is the manual one that I think is giving you the grief.

Manual limits have a little red-color push button; they should be located close to where the burners are (at the bottom of the burner box Trane says), and this is b/c it's job is to monitor the flames and/or abnormally high temperature conditions.

I cannot help blind, some pics would help me help you pinpoint the location of these. With both cover doors removed, pics of the upper and lower compartments will help much.

You do not mention the green light. What is it doing while the red one is blinking?

I'll be heading for work soon. At work the firewall we have won't allow me access to photos (I can read text but cannot see pics), so I'll get back to you at the end of the day...but perhaps someone else here at the forum may be able to help in the meantime.

 

I have the unit completely off now, and it is blinking steady red, the green light is now binking steady, half as fast as the red blink. The green light was not flashing when the unit was on.

 

You have a downflow unit. I suppose you have floor supply registers and ceiling (or high sidewall) returns...likely in a house with a crawl space but no basement. Maybe even a 1-story residence

The picture did not help me trace the location of that manual-reset limit, but the schematic indicates it is by the burner box and the wires leading to it should be yellow.

Please look below at the white arrow I have drawn, notice the yellow wire it points at...follow this wire to the right...look next at the yellow arrow I have drawn...to the left of this yellow arrow and behind the gas valve I believe the yellow wire ends by this limit switch which I cannot see (I have added the text "gas valve" to it so you know what I mean)

The burner box is that metal box underneath the gas valve...the one that has that sight-glass in front, and the rusted-out top.



Manual reset limits look similar to the control shown below. The little red button that the arrow is pointing at is what I believe has popped out and needs to be pushed back in in order to be reset



I hope this solves your problem, else I'm going to need close-up pictures. If it comes to that, I'll let you know where I want those close-ups taken at.

Sorry about the delay, long day...I just finished feeding the youngsters over here...and as I mentioned, the firewall does not allow access to pictures at work

 

First off let me thank you for walking me through these things, seems like the problems always start with my dh leaving. Anyway, looking at the weather, I went ahead and called someone in. There was a blockage in one of the drainage tubes. There are two bad switches. They are coming tomorrow to fix them. It is going to get cold again!! Stinks when I could not get it done myself (with your help)

Thanks again very much!

 

About the drainage I was going to talk to you next, after taking care of the defective limit(s).

Notice the top of the burner box? notice that it is all rusted-out?
That is not normal and if left unchecked will shorten the life of your furnace ($$$). That rust tells me that there has been some dripping from above and for some time. What is above of this burner box? the inducer blower, located inside that black plastic box...and there's a black drain line moving left and downwards, and ends on top of that white plastic box to the left of the burner box, which is called the "condensate trap". That's where the drain lines end.

Glad to hear you're gonn'a have it fixed. Sorry I could not get back to you earlier.

 

Nope you were great. It is really awesome that you work all day and them post on the forum to help others. That is a wonderful way to pay it forward, hopefully you have gotten many good things in return. I hope you realize what a valuable resource you are offering!

I am going to talk to the guy in length tomorrow when he comes to fix things.

I understand about it being busy, I have a 12 year old dd and 3 year old b/g twins. The day never seems long enough here!