I have a customer with a Trane gas furnace model# TUY100R9V4W5. I believe it was installed in 2005. They have had to have the ignitor replaced 3 times already. The first time I talked to Trane tech support I could not get a lot of information out of them other than they have changed the part number for the ignitor three times. I take that he was implying that they are just defective ignitors. The guy at our Trane supplier said that the boards on these particular models step down the voltage to the ignitor to 80VAC, and they have found some boards that fail to do this and thus send too much voltage to the ignitor, causing premature failure. I recently checked this out for the customer (I am not the one who did any of the repairs previously, just following up for them to try and resolve this issue) and found that the voltage to the ignitor fluctuates between 86VAC and 121VAC. I have a Fieldpiece multimeter that updates about every second, and the readings look like 86...94...121...86...94...121...etc, the entire time the ignitor is energized. At this point I am definitely leaning towards replacing the board (they have 10 year parts). I can't imagine these readings would be normal. I will be talking to tech support again on Monday morning but I wanted to throw this out here to see what any of you Trane experts think. I work for a Carrier and Lennox dealer and I just don't see a lot of Trane furnaces, and have never run into this problem.