Another Aqualink Sensor problem

[Tubbs]

Getting either freeze protection or Air Sensor open message. Been fighting this for a year or so originally replaced the air sensor and it was good for 6 months or so. Purchased another and it worked for a week. Wired in a 0.5 Watt resistor and it worked for a week or two and now getting the ASO message or freeze protection kicks on. I am thinking it must be the board. I have cleaned all the contacts rust isn't an issue here in the desert. I would like to get it diagnosed before I start throwing parts at it.
Edit to add: It is a RS8 and has been in use since 2001

 

[generessler]

Hard to say, but sounds like an intermittent broken connection. Given you've re-made the wiring several times, the next thing to suspect is a cracked solder joint or circuit trace on the board. Typically a hairline break. If you can get things working by wiggling the screw terminal block where the sensor attaches, Bob's your uncle. These failures are often easy to find after removing the board (maybe with a magnifying loupe) and fix in a couple of minutes with a soldering iron. If you succeed with the "find" part and post a photo, I can explain the fix.

 

[Tubbs]

Hard to say, but sounds like an intermittent broken connection. Given you've re-made the wiring several times, the next thing to suspect is a cracked solder joint or circuit trace on the board. Typically a hairline break. If you can get things working by wiggling the screw terminal block, Bob's your uncle. These failures are often easy to find after removing the board (maybe with a magnifying loupe) and fix in a couple of minutes with a soldering iron. If you succeed with the "find" part and post a photo, I can explain the fix.

Hopefully thats all it is, So if the board had a bad component it would be giving the open air sensor message continuously?
As it is now you can put it in service mode overnight put it back to auto and it works normal for a day or two.

 

[generessler]

Hopefully thats all it is, So if the board had a bad component it would be giving the open air sensor message continuously?
As it is now you can put it in service mode overnight put it back to auto and it works normal for a day or two.

This is all a guess, but working for a couple of weeks after replacing a sensor says to me that the sensor itself made no difference, but applying force to the board to connect the sensor did. Might be the same with pressing the service button. All you're saying is consistent with a connection that's okay most of the time, fails after a while when exposed to air and temperature changes, but is easily re-made with any kind of physical jiggle. You're going to be removing the board anyway to replace it (which is the next, next step), so I'm mainly saying check it carefully for a simple connection break that's easy (and cheap) to fix. OEM boards (which you need to use) are pricey.