Water Heaters - My power vent on water heater keeps running

I have a Kenmore Power Miser 9 50 gallon water heater with Power Vent which is almost 6 years old. I noticed yesterday when I came home from work that the power vent was running, and since both my wife and I work during the day it tells me it had been running since early in the morning after the wife took a shower.
I tried running hot water for a few minutes in order to kick the heater on to produce hot water, but it did not go off (generally runs 5 mins or so after using enough hot water to kick the burner).

Since I really do not understand these things, I will appologize now if I ask a stupid question. I assume there is some sort of switch or sensor that detects when the burner fires up, thus allowing power to the vent. Then, that same switch/sensor detects when there is no more heat and shuts the voltage off to the vent. Am I close?

Below is a direct link to the parts breakdown of the entire unit. I was thinking of ordering a new pressure switch to see if that would work. Not sure what is involved in replacing one though. Can I do this myself?

KENMORE | Model #153335916 | POWER MISER 8 POWER VENT GAS WATER HEATER | WATER HEATER | SearsPartsDirect.com (http://www.searspartsdirect.com/partsdirect/retrieveModelActionHome!retrieve.action;jsessionid=PmlzXId-esfl+Q6XzoC1YQ**.shcapp3006?modelNumber=153.335916&pop=flush)

Any help or suggestions would be greatly appreciated. In order to save electricity and wear and tear on the vent, I shut the gas and pilot off and unplugged the vent after the Mrs. took a shower this morning.

Ah, the joys of owning a home :(

you might be better off calling tech support since this isnt in the troubleshooting portion of your owners manual.

i could probably figure it out if i was there but it has been a long time since i have worked on one of these and i forget what could cause this problem.

i know i have seen it before but ..... well im getting old to say the least and dont remember

Thanks.

Replace air pressure switch and nothing. Others have told me it may be the gas pressure switch. I will try tapping that tonight, but I have a plumber coming on Saturday to check it out as well.

http://www.managemyhome.com/mmh/lis_pdf/OWNM/L0030142.pdf

On page 15 there's a schematic. Looks like only 2 things make the fan run, on/off switch and gas pressure switch.

I've got the same problem except mine is a State Select 50 gal. gas water heater, model #PR650N0VT. We've pretty much determined it is probably the gas pressure valve that is defective. However we are having trouble finding anywhere which handles these parts for a State Select. Can anyone help us out finding out where to go for parts w/o going to a plumber, preferably wholesale or even retail would be good at this point.

bloomune_59, are you sure about that model number? state does not show an novt in any of their model numbers

Just had the plumber come by. He looked at it and said it is more than likely the gas switch, but he is not sure his boss will want to mess with a Kenmore unit. I wouldn't know until Tuesday. They would install the part if I were to get it right from Sears. It looks like the burner and gas valve are all 1 assembly.

Since I am 1 month over my warrenty period, I will need to pay for everything. He mentioned getting a new heater, and was really pushing a Bradford White unit, 50 gallon power vent for $1200 delivered, $1700 installed. I thought that was a little crazy, even if I am going to install it myself.

I have a few options, but if the part and burner assembly is probably a good few hundred dollars and my unit is now out of warrenty, do I just buy a new heater? I have some number crunching to do, but putting that aside, what are some decent name brands you guys recommend? Is BW a good name? How are Rheem units? I believe this unit cost me under $800, but that was 6 years ago.

He also mentioned a RINNAI tankless installed for $2000, but then the tax credit is 30% through 2010, so another $600 back. $1400 installed.

bw is my preferance but rheem (ruud) is a close second. do not and i repeat do not buy a whirlpool from lowes. they have a problem with the burner assembly on the firv units which is the new technology you will get when buying a new heater and is part of the higher price. 1200 is kind of high but then their mark-up and probably getting one of the super efficient heaters to boot i could see that price easily

Thanks

Well, I had the blower off starting yesterday afternoon and did not turn it on until this morning when the wife wanted to take a shower. Fan went on and so did the burner. It ran for 15 mins or so and then shut off. WTF? It is back to normal now. Must be something sticking, but it cycled again when I took a shower and went off.

I may have dodged a bullet for another few days, maybe weeks which will give me time to learn about the tankless units.