Temp gauge adjusting?

Forrest39

Forrest39

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CAT Member
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My car indicates 200º on cold days as well as hot. I got a laser temp gun and hit up a few parts of the cooling system. Most (most importantly the thermostat housing) show 180º. Is there a way to put a VR pot inline or in parallel to trim the signal to make the temp indication more accurate?

Thanks, -Kevin
 
Check what temp sender you have and where is it mounted? What about grounds to gauge and voltage stabiliser?
 
michael-king said:
Check what temp sender you have and where is it mounted? What about grounds to gauge and voltage stabiliser?
Click to expand...

Not sure what sender it is. I had assumed there was only one kind. The intake is an Edelbrock Performer RPM and the sender is located on the forward left part of the manifold between the distributor and left cylinder head. I just measured the resistance at ambient temperature and it indicated 711 ohms. My neighbors wouldn't be to thrilled with me firing it up and brining it to normal running temperature this late so I will have to wait until Friday when I get home to get the nominal resistance value.
As near as I can tell, that portion of the wiring is unmolested and the voltage stabilizer is correctly installed and the gauge is well grounded.

Cheers, -Kevin
 
Infrared temperatures

Forrest 39
I would advise some caution in believing the measurements your infrared thermometer is reporting. Unless you know the emissivity of the material you are measuring, you should place a piece of black electrical tape over the spot you want to measure the temperature, and then aim your instrument at the tape. Black tape has an emissivity very close to .95, which is where most low $ IR temperature instrument are calibrated. This way you'll get a more accurate temperature.
 
The original voltage stabilizer is a very 'lo-tech' mechanical device that takes the 12 volt input and ( hopefully ) outputs an average of 10 volts. If it puts out more voltage, both your water temp gauge and fuel gauge will read high. I would try and rule that out first...
 
All good ideas...

I'll try the tape and also drop a mechanical thermometer into the expansion tank and see how that reading compares to the laser value on the tank.

The fuel level indicator level seems to reasonable, but I'll look into the stabilizer further.

Thanks for the input! -Kevin
 
After receiving several water temp senders from Rick that were way off I decided just to match the temp on the gauge to the IR on the exit hose near the sender by adding resistors in line. I think it took about 53 ohms. Once I got the stack built I installed it behind the dash directly on the temp gauge. On either ends were 1/4" spade terminals, one male and one female.

I doubt the temp in the expansion tank matches the temp at the sender so I'm not sure what that mechanical gauge will tell you.

bt
at the beach
 
Wow

Not to toot our own horn but I remember reading this and just this week borrowed a I/R MAC tool thermometer. It was easy to find this post with a keyword and a tag search.

Well holy crap I have a Tiger that runs too cool and the gauge is way off. Now I am tempted to see if the PO put in a 160 thermostat or maybe a email is the lazy mans way for now. It has a early Dale add on Davis with no expansion tank, which I was going to add back as I like the look and I thought it was running hot. My VW like test of how long you can hold a 190 degree dipstick test was always in question. "Been 20 years since the VW has run." I think my fingers n brain forgot the number of seconds you can lay your hand on a air cooled alloy head.
A feat I still perform with my toy Honda motorcycles but only once a month in the hash Cali winter and Spring.:D

The stabilizer is not suspect as yet as I have not voltage tested it but the fuel tank maybe under reads when tank is full " yard stick and eye ball" method.

Got too many other projects now so maybe it will be like the old AM radio without presets and a fickle tuner a small line of tape at 180 :D

Oh PS is there a small marking on the temp sender usually? got to find the reading glasses.
 
Temp Guage

Mine reads 10 degrees high. When it show 190 it is actually 180. Thought about bending my needle a bit.
 
I would rather have my gauge read high than low just for a little insurance on those hot days. Good info on how to get a correct reading with a temp gun.
 
at the beach said:
After receiving several water temp senders from Rick that were way off I decided just to match the temp on the gauge to the IR on the exit hose near the sender by adding resistors in line. I think it took about 53 ohms. Once I got the stack built I installed it behind the dash directly on the temp gauge. On either ends were 1/4" spade terminals, one male and one female.

I doubt the temp in the expansion tank matches the temp at the sender so I'm not sure what that mechanical gauge will tell you.

bt
at the beach
Click to expand...

My temperature gauge reads pegged at 250 and is actually 188. The previous owner apparently added a resistor in line that did not fix the problem. Would a new sending unit fix the problem? If so, who has this part?
 
Resistance is futile

Not really could not resist;) Below is a copy from another site and some values of a original sending unit by Stu Brennan on the Classic Tiger site
http://www.classictiger.com/techtips/gageohms.html

It is copied here as links sometimes go away sounds like a good idea to match a subsitute sending unit as close as possible to the English made gauge


Fuel Gauge Gallons Ohms 2 145 4 80 6 55 8 38 11 21
Temp Gauge Degrees C Ohms 60 150 80 77 90 57 100 41 120 24
 
Thats good data to have Warren, thanks.

I'll throw out a quick C to F conversion formula that we often use at work as almost all weather reports are in C.

Example, 20ºC -- Double the value (40º), subtract 10% (40º-4º=36º), add 32º (36º+32º=68ºF).

Happy Friday! -Kevin
 
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