Realistic Center Vent Temperature of "WORKING" A/C

[Gruber]

Where do you read how is accurate ? where is % accurate ?
You mean easy to read.

Well, exactly. For $6.99 and with the range from -50 to 300 °C it is likely a K-type thermocouple (like the probe in most multimeters), so it can easily be off by several degrees.
You won't know until you check it.

Indeed the mercury type has been for a long time the relatively cheap and at the same time accurate thermometer, but they are now mostly retired and hard to buy. NIST stopped to calibrate them. But if you broke one in your AC vent, you would probably freak out and sell your car because of mercury panic.....

A calibrated digital thermometer with a guaranteed (even very mediocre +- 1 degree) accuracy can't be bought for $6.99. But you can check your cheap thermometer's accuracy yourself...

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[SCOPESYS]

Well, exactly. For $6.99 and with the range from -50 to 300 °C it is likely a K-type thermocouple (like the probe in most multimeters), so it can easily be off by several degrees.
You won't know until you check it.

Indeed the mercury type has been for a long time the relatively cheap and at the same time accurate thermometer, but they are now mostly retired and hard to buy. NIST stopped to calibrate them. But if you broke one in your AC vent, you would probably freak out and sell your car because of mercury panic.....

A calibrated digital thermometer with a guaranteed (even very mediocre +- 1 degree) accuracy can't be bought for $6.99. But you can check your cheap thermometer's accuracy yourself...

"But you can check your cheap thermometer's accuracy yourself"

Exactly -- you are only really interested in the low temperature accuracy, near freezing .. so it is easily to check if there is an offset around freezing, but putting it in a cup of Ice water.

But you are not really that concerned with absolute accuracy.. as your vent temperature will change with so many factors, such as outside temperature, humidity etc.

What is of more concern, if that the low temperature your A/C can get to in a given conditions, or if it starts to rise significantly over time -- which would indicate there is a fault developing in the A/C system

So, as far as I am concerned, the cheap $6.99 is more than adequate, and is quite accurate enough for the purpose it is going to be used for.

 

[SCOPESYS]

Finally found some Inexpensive, Black Plastic, Deg F, small, digital thermometers.

Got two, and fitted one to the SI, and the other to the Maxima,
How I can keep an eye on those vent temperatures, and hopefully get some early warning if they are starting to rise (probably due to Condenser leaks in the Si)

Dark Gray case of the Temperature is an almost exact match to the Honda Plastic, and it does not look too "out-of-place" where I mounted it with some extra strong double sided tape.

Tried Velcro, but it was to wobbly !!!

(Old Samsung Smartphone has a useless camera... but is fine as a wifi-hotspot in the car, and is just about as dated as the Honda's Head unit, so they are a good match !! )

https://www.ebay.com/itm/Digital-Re...rmostat-Oven-Thermometer-Freezer/202737667944

China unit -- I bought it from a USA Ebay seller, if you can find it from China, it should be less expensive. (Unless the Tariffs are already through the roof !!)

My thinking is that if I can tell when the A/C in the Honda is starting to fail, it should be BEFORE the lack of Refrigerant (and oil) causes an issue with the expensive to buy & replace Compressor.

By the time the Low pressure switch is working to stop the Compressor from even starting, the refrigerant has decreased to a damaging low level, and damage has probbaly already occurred to the compressor,


The CONDENSER, which seems to be the part that initially fails, is not that expensive, and is quite easy to replace.

 

[whymi]

The real way to test is not from vent temps, but by measuring temp differential between inlet and outlet temps at evaporator lines. But another good way to test efficiency is at center vent temp, on max ac setting, recirc, all doors open
System running about 10 min. You'll want to see no less than 30 degrees less than ambient temp.

 

[cwradio]

My 2016 Honda Civic EX (non turbo) meets all the spec in the above picture ( Scopesys Sept 2 post). 43F at low fan speed and 53F at max fan speed when car is in driveway. Outside temp is 84F Humidity 45%

My problem is when I drive the car the vent temp is about 54F and fan is high (in auto mode) Outside temp is 84F. humidity 45%
Replace cabin filter at 34,000 miles. No warranty left on car. Over 36 months

Any advice? Thanks Paul

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