Carrier RAV Intermittent Problem (Help!)

ezmamos

So I have a Carrier 58RAV furnace installed circa 1996.

I will try to make a long story short.
Originally upon turning the thermostat on the igniter never even got hot. There was signal from the thermostat but nothing after the board (even when jumpering the appropriate pins on the board). I replaced the main board (with a newer model with the diagnostic LED). After I replaced the board it worked for a few days but then it stopped working and the problem became more intermittent but the same problem where the igniter wouldn't even get hot. Wiggled the 12 pin connector attached to the board and it would work right away and then would stop. I took the connector apart pin by pin and used fine sandpaper and contact cleaner to clean, recrimp and otherwise adjust the pins. There was visible browning of the pins. Worked for a couple of days and then 2 days ago, it stopped again. I went up to the attic and that's when I started getting the current error code 34 and then subsequent lockout with code 14. Now however the igniter turns on but then just shuts off. Not like before where it didn't even get hot. I cleaned the flame sensor with fine sandpaper and it worked until this morning. My next step is going to be changing the flame sensor (especially since it's only $15).
What is left if that doesn't work? The igniter and the gas valve. The blower always seems to come on and the filter is clean. Any help would be very much appreciate to me, and my very cold family.

Eric

redline

Did you check the drain tube for a blockage?

ezmamos

No I haven't yet...then again I'm not sure how. I know there are two PVC pipes going in. I went looking for the flame sensor but the two HVAC wholesellers I went to did not have it. Could it still be the flame sensor or am I completely off track?

bigMikeB

The flame sensor has nothing to do with the igniter getting hot or not.

ezmamos

I understand that the flame sensor has nothing to do with the igniter. I don't think that there is anything wrong with the igniter. I'm just trying to see if I'm on the right tracks being that I replaced the control board already.

bigMikeB

WRONG TRACK, nothing you mentioned points to a flame sensor issue. Does the igniter get 120v for 45 seconds?

ezmamos

I thought the flame sensor because if the flame turns on and then off, that the sensor was reporting no flame and turning the system off. I didn't know about the igniter having to receive the voltage for a given time. I thought once it got hot and the flame lit up that was it. So basically clip the leads of my multimeter to the wire going to the igniter, light it up and check voltage for 45 seconds. If it doesn't get the proper voltage for 45 seconds then replace the igniter?

bigMikeB

You didn't say in your post that the flame came on and then shut off, you said you had an issue of the igniter not coming on or getting hot.

ezmamos

..."Worked for a couple of days and then 2 days ago, it stopped again. I went up to the attic and that's when I started getting the current error code 34 and then subsequent lockout with code 14. Now however the igniter turns on but then just shuts off. Not like before where it didn't even get hot. I cleaned the flame sensor with fine sandpaper and it worked until this morning. My next step is going to be changing the flame sensor (especially since it's only $15)."...

ezmamos

So today, we had to bite the bullet (well at least a little) and call somebody out. We found a company that charged only $79 to diagnose the problem and would apply it to the cost of fixing if we had him do it. He first thought it was my replacement board which was after-market and not an original Carrier but I didn't think he was correct. To his credit though he didn't just blow me off but continued testing. He is now 100% sure that it is the valve. Mechanically it seems ok but it closes in the middle of the cycle for no reason. He put a meter on it and the board was sending 24v to it however it still closed despite having continuous voltage. He said that the reason he thought it was the board was because he was used to the "timing" of the Carrier board and the way it's cycle went. This board cycle times were different. So unfortunately he wanted $550 to replace the valve so I had to say thank you and that I would do it myself. I'm afraid I can't quite afford that at the moment. So tomorrow I will try and pick one up (luckily in Los Angeles there are a lot of HVAC parts and wholesale shops) and install it. I will post if it works so the next guy will have an easier time searching than I did.

bigMikeB

I read that but, the burners light off and then shut down in a few seconds, would be a sensor issue. Which isn't in that description. The guy you had out might be a nice guy but telling you that the timing is different on an after market board isn't true. If they sold you a board with different timing than the original, they would be solely liable for any subsequent damages caused by that timing difference. Many companies such as ICM make pc boards to the original specs as soon as the patent runs out. They function exactly the same.

ezmamos

bigMikeB...my apologies. I don't think I was clear. Sometimes the igniter would turn on and then off but also sometimes the burners would in fact turn on and they too would just shut off. The igniter always got hot though. Now this was when it was not working. There were periods when it would work for a few hours or even days and then stop. You're right about the guy though. Nice guy but I can't comment as to the comparison of the timing of the two boards. It's not like I'm so in tune with them that I could tell. He also, I think, tried to use some scare tactics telling us that the ducting was very poor and there were stress fractures on the fire box (heat inducer) and that it was his "job" to tell us especially since we have a 2 year old. I'm not really sure what he was talking about. Maybe I'll install some carbon monoxide detectors in the house...probably a good idea anyway. The thing is my parents furnace in the house I grew up in was the original from 1920 and lasted until 1990. I have a hard time believing that my 12 year old furnace is at the end of it's life. Anyway, his diagnosis of the problem seems to be working so far. In fact before I went out today and bought one I was able to replicate what he told me. I put my meter on the valve and kept turning the system on and off until it failed. When it was failing the thermostat would call for heat and the cycle would start. You would hear the valve click and I would see voltage on it but then no gas (or there was gas for a short time and then the valve would close) even though there was still 24 volts on the valve until the flame sensor signaled the board to cut power to the valve. I replaced the valve today and so far so good. I did buy the flame sensor since it was only $20 and I'll just keep it around just in case. So the board was $90, the valve was $80 the flame sensor was $20 and the diagnosis was $80 so all in all I spent $270 which is still less than half the $550 they were going to charge me to change the valve only. I'm sure changing the board would have been another five or six hundred dollars.
Now that I think of it he said one more thing which I don't know if he was trying to blow more smoke up my ass. He said that a proper installation of the ducting doesn't even use dampers at all for balancing the system. That if he did the installation he wouldn't even need them. I find that hard to believe in normal size house. How would you balance the system otherwise. Different size ducts for rooms that are at different distances? Anyway, thanks for the help. Two weeks ago I knew completely nothing about furnaces so at the very least my money was well spent on my learning this.

bigMikeB

As for your parents furnace, they don't make em like that anymore. Theirs had cast iron and heavy sheetmetal parts, yours has lite sheetmetal and plastic. But, yours is much more energy efficient.
Glad you chalk this up to a learning experience. Good luck.