Temperature gauge reads 230 but I checked it with a gun and the thermostat housing was 190. I have a new delco button head installed. The gauge works good from cold to 230 it is just to high. I tried to find the post that had a simlar problem.
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Lyle
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Re: Temperature Sender-73
Lyle----
If you're using current Delco temp sender GM #12334869, that unit has been reported to consistently produce high temperature readings when used with original guages. I suggest you obtain an NOS GM 1513321 or use an aftermarket sender of Napa or Standard Auto Parts #TS-6In Appreciation of John Hinckley -
Add-on
Great advice from brother Joe, but the sender isn't the only 'culprit' in the temp gauge system.... However, Joe's suggestion(s) are probably 90% in my sphere of experience!
The gauge itself was factory calibrated to read a given temp at a given branch circuit current flow. It wasn't really intended to be a 'precision' electronic thermometer across it's full dynamic range, hence the lack of intermediate gradicules (something in the 'cold' range, something else marked around mid-scale, then quite reasonable detail at the upper end where the gauge indicates bona fide overheat). It's the high end (overheat), that designers cared about and that's WHERE the gauges were hand calibrated to be accurate at!!!!!
Early gauges (before your '73) were calibrated by installing the gauge in a controlled voltage/current supply fixture and assembler installing the pointer needle to indicate the OVERHEAT position. Later gauges (like your '73) were placed in a similar fixture and precision wire wound 'shunt' resistor was installed on the guage to force an accurate high end reading.
Now, all bets are OFF if a prior 'budda' has been in the instrument cluster doing 'restoration' or 'repair' by component substitution. Why? Well, I don't know how a restorer can re-silk screen the gauge face without removing the pointer needle (kiss either form of factory cal bye bye). Plus, if a later era gauge's shut resistor has 'blown' (they work nicely as an unintended protective fuse when mechanics FORCE a bypass of the temp sender to ground then walk around to look-see if the gauge needle has pegged) OR the gauge was swapped for a replacement and the original cal shunt resistor got left out or was mixed up with the prior one.....
That's one of the reasons folks who sell temp senders simply won't guarantee them for accuracy with a given car's gauge even if they meet their original AC temp/resistance spec.... It takes two to 'tango' and BOTH the gauge and the sender have to be in spec for the system to work as it was intended.Comment
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Re: Add-on
Jack:
Am I to understand you to mean that pre 1973 cars did not have shunt resistors installed on their temp gauges?
My 1965 certainly has. The problem is, that the higher the shunt resistance, the higher the indicated temp is, so, there is no way to trim the existing shunt resistor to a lower value, short of performing delicate surgery to shorten the resistor wire as needed.
In my case, I added a variable t******* resistor in series with the signal lead coming back to the gauge from the sender, and adjusted it, so as to register an indicated 180 degrees, at a measured (via IR instrument, aimed at the temp sender interface with the intake manifold) 180 degrees.
JoeComment
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Re: Add-on
Joe tell me where you bought the variable unit and a part number . I have tried two gauges and four senders but all I have in it is time so far and its snowing anyway.Lyle
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Re: Add-on
Radio Shack - 0-100 ohm variable potentiometer (a.k.a. volume control), about six bucks; they may have to order it, as it's a low-demand item - mine has B100(ohm symbol) ink-stamped on the back. Also makes a great diagnostic tool for fuel gauge problems (replicates the tank sending unit when inserted between the gauge sender terminal and ground).Comment
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Re: Add-on
Lyle:
As John said, the resistor is a 0-100 ohm variable. I do not have a part number for you, but I found mine in stock at Radio Shack, 2 to a package. The resistor is blue, and measures approx 1/4" x 1/4" x 1". It can be adjusted with a jeweler's screwdriver. Sorry I can't be more specific. I dialed mine in to 37.7 ohms @ 60 degrees (resistance will vary somewhat with temp). My car is a 1965, so your 1973 will probably require a different value. I set mine to be "dead nuts on" at 180-190 degrees, but, there is no way to prevent variations at both ends of the scale.
JoeComment
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Final Results
New GM or Standard may be the same mfg as both have small 45 stamp on them and read 230 degrees installed. Wells TU-5 160 degrees. Reinstalled new GM and added 0-100 POTS ( potentiometer) dialed to 190 and checked with gun to check real temperature. I now hope it will show an overheat condition if I have one. Thanks allLyle
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