Temperature Sendor Replaced but running hot

[mightyatom]

This is to close off the thread as the issue is now resolved. The NOS temperature sender from American Classics fixed the issue, and is now running no higher than mid-gauge. The last update in this thread said it was running too hot again but this we due to air in the system. After back-flushing the cooling system and refilling I did not see the overheating issue and have driven on a few longer trips now.
When I refilled after the back-flush I made sure I was parked diagonally on an uphill slope. I also put the passenger side wheel on a ramp so the radiator cap was the highest part of the cooling system to ensure all the air was out. I cycled a few times of fill, run till hot, let it cool. After this it ran fine.

Neba also contacted me and he has had a similar issue with the Kragen(O'Reilly) temperature sender (Part#WT231 - I think). He has added a 50ohm resistor which get it running a quarter up the scale.

I would never have thought that new temperature senders would be the cause of the issue. I guess the lesson is, don't take anything for granted.

Many Thanks for everyones help on this. You guys are awesome.

[mclairmo]

Read the below that I found from Corvette Specialties of Maryland, Inc.

Can you repair my temperature gauge?

It reads high, but my 'Vette is not actually overheating.

COMMON CUSTOMER COMPLAINT: (Applies to all Corvette electrical temperature gauges from 1955 to approximately 1972.) Customer will usually add the following: I know it's not the sending unit. I've already replaced that.

REALITY: ALL, (I mean ALL), each and every new sending unit that is sold presently is wrong. I don't care what the parts guy tells you or what the parts manual says, they are wrong. There is an exception to this, which is to find a New Old Stock (NOS) part. To my knowledge, these parts have not been available for at least 20 years. Our testing of a known good original sending unit and the currently available part, shows that both units read nearly the same - until the water temperature reaches approximately 180 degrees. From that point and higher, the correct sending unit will maintain accuracy, but the replacement unit will give you a reading that is approximately 30 degrees higher than the actual temperature. Unfortunately, in our opinion, the addition of a resistor (to alter the reading of the replacement part) is inappropriate. The readings are not consistent throughout the normal temperature scale. They do not vary (enough to be a problem) until approximately 180 degrees. For those of you that have a car that rarely exceeds 180 degrees, you will not notice an inaccurate reading with the replacement sending unit.


SOLUTION: We currently have a GM licensed reproduction sending unit with correct calibration for $22.00 each. The appearance is like the original, including the wording "A.C.- Made in USA.-12 Volt". You may also replace the sending unit with an original type. It may sound difficult but through research, we have found that many GM products from the 50's and 60's used a sending unit that will work in your Corvette.

I also read another article that explains that the newer AC Delco G1852 water temp senders are the same as all the aftermarket one and are wrong. As such, if we are using these new aftermarket units, our guages will be wrong. I am going to buy the repro Corvetter one and see if that is accurate.

[neba]

after trying 2 WT203 senders i used a DELCO G1852 sender and it solved my problem. guage now reads about mid scale. 50 ohm resister also seemed to work

[mclairmo]

Did you use a new G1852 or an older NOS version that was made many years ago? I have read that the newer ones are the same as most of the aftermarket ones.