How to test my switches - http://www.hvacmechanic.com/ Forums
Original message
| hellbilly
 |  "How to test my switches"
, posted Sat 24 May 09:44  
I've been troubleshooting my furnace problem, with the assistance of this forum. However, I am not sure if I'm testing my switches properly. When testing the roll out switch, and the pressure switch, am I supposed to simply make contacts with the tester to the wire going out and the wire going in? Or, am I supposed to disconnect one and test across the gap? I just wanna be sure I'm doing it right so as not to make an improper diagnosis. Thank you.
|
|
Replies:
|
| theduke03
| "Re(1):How to test my switches" , posted Sat 24 May 09:57
Check with wires connected. 0v=switch closed, 24v= switch open. Pressure switch will not close until inducer is up to speed.
"My dad was the most feared furnace fighter in Northern Indiana."
|
| | hellbilly
| "Re(2):How to test my switches" , posted Sat 24 May 10:28
Thanks again Duke. I was doing it right then. All my switches read zero. Just now while I was testing again, I finally got a very brief fire up. I had the electronic gas switch turned off, and when I flipped it back on, it worked for about two seconds. Then went right back to the same old crap and would not fire again. And I'm not getting any volts at the electronic gas switch. It must have had power for those two seconds right? But I didn't have the tester on it right then. So is it the board or the electronic gas switch? Seems like the board to me, but I'm not the expert. Are there anymore test I can run to confirm the board failure?
|
| | theduke03
| "Re(3):How to test my switches" , posted Sat 24 May 11:43:
hellbilly, Your switches are closed so that is good. Do this in this order: Shut off furnace. Disconnect the two wires from gas valve. Jam your meter leads into the connectors on the wires so that you dont have to hold them in place. Make sure the wires do not touch each other or anything metal.
Turn on furnace.
Make sure LED is flashing code for"normal/call for heat".
When ignitor is red the board will either give you 24v, or not 24v. Since there will be no ignition, board will only send 24v for a brief period(5 seconds+/-). If no 24v, bad board. Reset furnace and repeat as many times as you want until you are convinced.
Post results.
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Sat 24 May 11:58] |
| | hellbilly
| "Re(4):How to test my switches" , posted Sat 24 May 12:26
All right Duke. I did it. And there wasn't so much as a twitch on the needle of the tester. Just for the record I have the tester set on 50, between 2.5 and 250. Unless I'm mistaken that's the correct setting for this, isn't it? And since the board is sending no power to the electronic gas valve. This is why we think it's the board? Correct?
|
| | theduke03
| "Re(5):How to test my switches" , posted Sat 24 May 12:34:
If your meter has adjustable range it should be set so that the voltage you are expecting will be as close to mid range as possible. A 50 volt range is perfect. This is AC voltage. To verify that you are set right you should read 24v between R and C on the board with power on.
If your meter is set right, and the LED said "call for heat" and no 24v during ignition period,that is a bad board.
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Sat 24 May 12:35] |
| | hellbilly
| "Re(6):How to test my switches" , posted Sat 24 May 13:23
I guess I'll be getting a new board. So I have two questions. One, any suggestions as to where I can get on, online or elswhere? Two, could you tell me which one of all those numbers on the board, is the part number?
|
| | theduke03
| "Re(7):How to test my switches" , posted Sat 24 May 13:54
I don't know. You can find the board at any Trane or American standard supply house. Be prepared with furnace make, model and serial numbers. They can usually find the part with just the model # of furnace. For backup you should record all the numbers on the board and you're covered. I believe your board is called an IFC board(integrated furnace control). You can also purchase this online but you're on your own for that.
"My dad was the most feared furnace fighter in Northern Indiana."
|
| | hellbilly
| "Re(4):How to test my switches" , posted Sat 24 May 12:21
|
|
|
|  |
|
