Purged again and the O2 is down to the IM normal 2.1, will take some more readings with this unit on a known burner and see if the sensor goes to the depleted warning again, if it does I will use the cleaner and report back what happens.
Just remember to stick your smoke pump in before the FGA. If smoke is ok then it should be good for FGA, however if you stick the FGA in before doing smoke test and it’s not burning clean then this WILL cause damage to sensors
Notwithstanding the Nay sayers on here, anyone tried to clean an O2 sensor: Oxygen Lambda Lamda O2 sensor cleaner - new - for ALL CARS | eBay I have an old 327-1 with an out of date sensor may try to clean it with the above and compare it with my in date machine, should be interesting.
Used the cleaner and its seems to have worked, certainly when the message was displayed I took out the sensor and used the fluid and the message disappeared without re-purging, so good news so far, checked it against a calibrated unit and the readings where the same.
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Reply to the thread, titled "Testo 327-1 replacement sensors" which is posted in UK Plumbers Forums on Plumbers Forums.