Davis Vantage Vue - abnormally low (stuck) external humidity readings

[martinu]

For the past few days my Vantage Vue has been reporting abnormally low humidity readings - for a lot of the day and night it's stuck on 1% and then (usually around noon) it gets up to 40-80% for a while before gradaully falling back to 1%: http://goosebears.co.uk/weather/trends.htm. Until then, readings had ranged between 60% and 95% and as far as I can remember, had been highest on a misty or rainy day and lowest on a warmer, drier day - all fairly much as expected.

I've heard it said that abnormally high humidity (eg rain getting into the sensor housing) can block the fine "pores" that coat the humidity sensor. Is this true? If so, it is possible that the sensor will come good again?

The temperature readings (which use the same sensor block, inside the white baffles) seem to be fine. I've removed, cleaned and replaced the baffles, and dabbed the sensor with kitchen roll in case there was anything stuck to it.

The plate on the outdoor module says:

Product ID #6357OV
Model No 6250UK
Manufacturing Code 131113056

I'm not sure if any of those identify the revision level, because I see on another forum that early revisions had a separate unpluggable temp/hum sensor which coule be replaced, but later revisions ("progress"!) have the sensor hard-wired so the whole circuit blard for the module has to be replaced.

It's already been back to Davis a few years ago for the same symptom, when it was repaired under warranty, but I think it will be out of warranty now.


Luckily the only things it seems to affect are the humidity readings (obviously), the dew point which is usually around -40 deg C now and the estimate of cloud base which is now about 20,000 feet

[freddie]

Sounds like either component failure or a short? Typically, all else being equal, you should see lowest humidity midday to mid afternoon.

[philpugh]

I have just suffered this, for the second time in it's life, on my ancient VantageVue (circa 2009).

What I did, which seems to have resurrected it, is a total strip down of the Vue which gives you to opportunity to get rid of all the creepy-crawlies -including in my case a remarkbly large spider - not a lot smaller than the tipping bucket! Whilst in this state you may as well remove the wind speed unit and give it a good clean - mine had some grass lodged on the bearing.

The whole of the inside of the unit was damp due to very high humidity and low temps - which is possibly the root cause of the problem.

Just take care with the connectors from the sensors to the processor unit - these are held 'on' by pressure and and the board is coated with water repellent to keep the contacts dry. If you are really lucky it may be that one of these has 'failed' . Gently clean the contacts on the processor board and sensor cable and after re-assembly re-protect the contacts. I used a silicone spray to do this - just a little amount. But I guess you could use Vaseline or similar.

If you are unlucky the sensor unit may have failed - mine did the first time this happened and I had to buy a replacement. Depending on the age of your unit you may be able to get a replacement - I couldn't see one for mine when I checked after my unit started acting up last week.