How to calibrate temp gauge?

[Flamingo 5]

Suspiciously low temp makes me question if it works

[Schon '02]

Have you seen this?

[Mike Self]

8 minutes ago, Schon '02 said:

Have you seen this?

Right out of the BMW(no space)CCA 1976 Tech Tips book.  A most valuable resource for the '02 owner.

 

mike

[ray_]

1 hour ago, West Palm 2002 said:

Suspiciously low temp makes me question if it works

https://www.amazon.com/Kizen-LP300-Thermometer-Non-Contact-Temperature/dp/B07VSHR9M6/ref=sr_1_1?keywords=ir+temp+gun&qid=1583473094&sr=8-1

[dlacey]

I fitted one of these for an independent second opinion:

https://www.ebay.com/itm/Universal-Water-Tank-Cover-Radiator-Cap-With-Water-Thermometer-For-Excavator/153400903005

[Flamingo 5]

19 hours ago, mike said:

Right out of the BMW(no space)CCA 1976 Tech Tips book.  A most valuable resource for the '02 owner.

 

mike

Yes I’ve seen 

do you think it’s possible for my car to

run the interstate at 80mph for a hour

and never go over 165 degrees ?
mostly reading around 150

i do have a Griffin aluminum radiator 

Korman stage II

[Schon '02]

I’d check it with one of these for $16 before futzing with the temp gauge. 

https://www.amazon.com/Etekcity-Lasergrip-774-Non-contact-Thermometer/dp/B00837ZGRY/ref=pd_cp_328_1/147-5689337-3082223?_encoding=UTF8&pd_rd_i=B00837ZGRY&pd_rd_r=d39c3e8d-0f62-4b6c-ae15-f4eb09ead529&pd_rd_w=moiy1&pd_rd_wg=n6rHm&pf_rd_p=4853e837-f87a-46d4-be32-dcf86bff7a7c&pf_rd_r=D6BFPXCS8Q15EDSRR1S8&psc=1&refRID=D6BFPXCS8Q15EDSRR1S8

[John76]

Be careful when using a "bargain priced" Infrared thermometer.

The 12:1 distance to spot ratio of the Etekcity Lasergrip 774 means that it reads the surface temperature of a 1" diameter circle at a vertical distance of 12". It does not measure the laser dot!  This thermometer does not have an emissivity correction feature, so it is set to a default value of 0.95. This is OK for measuring NON-Reflective surfaces, such as black radiators, black hoses, black tires, paint, carpet, interior surfaces, etc. The wavelength of this unit is 8-14 microns, which is not suitable for reading shiny objects (aluminum, brass, stainless, chrome, etc.). Also, these devices only measure the surface temperature of the object it is pointed at. Surface temperature of a radiator hose will never represent the actual temp of the fluid flowing through it. That is why immersion sensors are used.

Just my '02- sense worth>>

John

[Flamingo 5]

I looked at the Chinese Radiator Caps

with Temperature on Amazon 

they look pretty crappy.

anyone use the Mr Gasket brand, if so

which one ?

 

[Schon '02]

“Low” temperature reading in the gauge could also be caused by the thermostat or temperature sender. The sender doesn’t typically go bad, but they’re inexpensive (<$10j if you want to swap it out; ditto the thermostat (~$25).

 

John76 makes a good point about IR gauge accuracy. I’m guessing normal operating temperature should be in the 175-180F range. If your dash gauge reads 150-165F, an IR gauge or temp stick giving you +/- 5F accuracy may be good enough to tell you if you have a dash gauge issue or not. 
 

FWIW, my gauge reads on the “low” side as well, maybe 170-175F per the TechTip. 

[jimk]

For those who are interested in digging deep, I have examined several temperature sensors from BMW equipment and the resistance curve was about the same for all. So here is some data from a data sheet.  (Sorry the headers are offset but the sane can interpret.)

Bosch Temperature Sensor NTC M12 data Sheet
°C	°F	Ohms
-40	-40	45313
-30	-22	26114
-20	-4	15462
-10	14	9397
0	32	5896
10	50	3792
20	68	2500
30	86	1707
40	104	1175
50	122	834
60	140	590
70	158	436
80	176	323
90	194	243
100	212	187
110	230	144
120	248	113
130	266	89

[2002#3]

How does one measure R real time with a meter, i.e., what should be connected to what, when the engine is at different temps as one makes correlations of R/temp and the position of the temp gauge needle?

Thanks.

[jimk]

Would bring up the engine to what is normal for that engine, lift the hood and pull the wire off the sensor, measure resistance sensor terminal to water manifold.

[2002#3]

Thanks, Jim. 

I can measure R as engine warms and plot increasing temps at approximate points (for my cars) between blue and red, like the the temp marks in the image in the second post.

Regards.

[Flamingo 5]

Thanks for all of your thoughtful answers.

would any of you know of a Bluetooth 

temperature sending unit that would 

work in a o2 ?