I need some advice and help.

I have a Trane XL90 (#TDC1008948A0).

It runs fine sometimes and then every now and then switches off and starts to blick orange on the led for about 1-2 seconds before trying to go green again. Sometimes it will eventually go green and light again but other times it then goes into flashing orange. I have never seen it on red though.

The flame when it burns is brilliant and strong. And it has been cleaned flame sensor etc.

I replaced the whites & rodgers box last year after reading that they had a tendency to fail and cause similar issues (reading of forums) It is a 50E47-843.

From reading the diagnostics from the W&R paperwork flashing orange says polarity reversed, I measured the voltage and the voltage says otherwise, so that just confuses me more.

Like I said at the beginning it runs fine sometimes and I have had a tech out to look at it and gave no issues but 40min after he left it started playing up again.

Any advice or direction would be greatly appreciated. I want to try and get it working properly before winter sets in or if I need to just bite the bullet and buy a new one.

Thanks in advance.
John

You might try to reverse the 24 volt low voltage leeds that come off the transformer. That trick has been know to work and is listed in some service manuals.

Thanks for the advice I haven't tried that yet but I was just out there before measuring voltages, whilst running fine and when it wasn't.
They were:
L1-TH was 95VAC
TH-TR 25VAC
L1 125VAC
GND-MV1 25VAC
GND-MV2 0VAC

The one thing I noticed was I was hearing like the gas valve click every now and then so I monitored the voltage MV1. When the machine was running fine it was reading 25VAC but whenever it 'clicked' the voltage would jump between 10-25VAC and then run solid at 25VAC then click again 16VAC then click and 0VAC where it stayed and that's when the orange light would first come on before sometimes restarting iteself or othertimes going into continual solid orange flashing(but all the other Voltages remain the same).

Does that mean that the gas valve is faulty? Or the other electrical component before the valve unit MV1 and MV2 go to it before going to the gas valve.

I hope that makes sense and you understand what I mean.

Thanks

If voltage is being supplied to the gas valve it should be open and operating. Now when the voltage drops or changes the gas valve should shut off. This is probably why your unit fires off then stops and starts. The voltage source is failing to provide a steady voltage to the gas valve.

You said you cleaned the flame sensor but clean it real good again. Steel wool or sandpaper (Very fine grit) will give it an almost polished look. The reason for this is the flame sensor generates a signal that the computer board uses. If the flame sensor signal varies that could cause a problem and in some cases the flame sensor might need to be replaced. Look in the manual/paper work that came with the board. It will give you the correct reading which you can use a meter to test the flame sensor out put. If out of range replace the flame sensor.

Voltage and grounds

This is also a major cause of intermittent problems with the style unit you have.
Check all grounds. Circuit board, case ground and the ground that goes back to your electric panel. Now I said ground not the neutral (white) wire but while you are at it it is always best to check them all. Now just do not look at them but loosen them up and retighten to be sure of a good ground. The electronics in the furnace are very sensitive to grounds that do not meet spec or proper contact.

I would also check to make sure the pressure switch isn't causing the problem, that would also break voltage to your gas valve. Maybe a partially blocked exaust or intake? Wasp nests in the exaust pipe etc...

hvac1000 - I cleaned the sensor again with fine wet and dry and when running it varies between 13.8-15.3V and when no flame sensed 30V. I checked the grounds and couldn't find anything wrong there either.

Hvacservice - there is one thing that I think is the sensor you were meaning with a micro switchon it but there is no way I can check inside it as it has a clear tube attacted that goes to another part of the unit no blockage from what I can see. As for the intake and exhaust are you referring to the blower motor. The intake is just got a wire screen on it and the exhast tube vents out the roof and has plenty of steam coming out.

I am again at a standstill something is not right but not sure what any other tricks I can try, I want to try and get it working right before it gets much colder and I can't really afford put a brand new system in just yet.

The only other thing that I am questioning myself about is I can't remember if it was doing it before I put the Honeywell programmable thermostat in.

Also on another not what system if I have to replace would be your recommendation.

Thanks again
Frustrated and cold
:(

Jump RH to W to eliminate the thermostat if you want to see if that makes a difference.

I made a jumper wire at the furnace between R-W. It still did the same thing where runs great for a while but thens still goes into flashing orange. It tries to restart itself without much luck initially but I noticed if I turn the main power off and then back on it tends to start again after its first attempt.

Thanks for the advice keep it coming I don't want this thing to beat me

John

Check the discharge pipe that goes outside. It is possible a wasp nest or something else is causing a restriction.

Did you ever reverse the low voltage leeds?

hvac1000 - I did not swap the low voltage leads, I wasn't 100% sure on where they were so I didn't go into it just yet. The micro switch that connects to the pressure switch that has a pipe going to it from the exhaust side of the blower but at the bottom where it goes into the furnace (hope that made some sense) is always clicking. I just jammed a piece of paper in there to see what happened and it was running (to me the longest it has) I ran out to check it and it was still going but from around the fan side of the blower it was bubbling water out I pulled the paper out and it clicked to orange.

From that correct me if I am wrong but I think I must have some sort of blockage in the exhaust pipe so I will have to cut it tomorrow and check.

Sounds like you found the problem.

HVAC1000

So I came home today cut the exhaust pvc hopped up on the roof and ran a hose down it nothing there whatsoever.

So there is no blockage on the exhaust side.

I have looked at the inlet of the blower motor and can see the rotor there too.

What could be setting the pressure switch off?

Not sure if it helps but here are some pics of the unit as well... Sorry for get that it didn't worki have pictures though