1962 Corvette Temp. Sending Unit
Help! The temp gage on my 62 goes to full hot after a mile or two and stays there. I have checked tha actual engine temp with both a thermometer and an infra red sensor and the engine is at a proper 185 degrees, where it stays for as long as the car is run. I have checked the gage itself by shorting the lead wire to the block and it checks out fine. I have purchased no less than 4 additional sending units (two new and two supposed good used ones), all with the AC logo on them. They ALL behave in the same fashion!! What's up with that? I have heard that AC is now sourcing them from China and that their quality is poor. Sooo--Q1: What should the cold resistance of a good unit read(in ohms)? Q2: I have heard about adding your own external resistor to, in effect, bring the gage into calibration---but this sounds kluge and a little absurd. Q3: Where can I get a proper(read--good) sending unit? The one I got from Corvette Central is new and malfunctions as above. Regards, Chuck
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Re: 1962 Corvette Temp. Sending Unit
Chuck,
The temperature senders (GM # 1513321) sold over the counter in the 1980's and 1990's apparently do not give accurate readings. In the 1980's and early 1990's I collected about 15 senders from various 1959-1967 Chevrolet junk yard cars & trucks. I did some research and noticed that the stampings on these original senders varied but I could never correlated these stampings with specific years (see photos). The "type" shown in my research is my own terminology.
As far as I know the only way to test them is to heat them in water at a varying temperatures and then measure the resistance while connected to a 12V DC source.
I have four type "G" senders from a "3799349" intake dated "K302", a "3844459" intake dated "C135", a 1967 Chevy truck w/283, and a 1968 Chev. truck 6 cyl.
The type "A", "B", "C", "D", "E", and "F" senders are from 1958-1961 Chevrolets.
The type "H" is NOS (purchased 1980).
The type "I" is NOS (box dated 1983).
The Corvette Restorer also has articles about temperature senders.
Vol. 11, No. 1, page 24
Vol. 16, No. 4, page 14
Vol. 16, No. 4, page 37
The GM 1513321 sender is NOT used with 1962-1967 Chev. Passenger cars w/"idiot" lights.
GM # 1513321 was replaced with GM # 546702 in Nov. 1970 which was then changed back to GM # 1513321 sometime in 1978 as per Chevrolet Parts History.
Dave -
Re: 1962 Corvette Temp. Sending Unit
Charles:
Your problem may not be in the sending unit, but could be an intermittent "short" in the tempertature sending unit to temperature gage wire when the engine gets hot. Grounding this sending wire will produce the same symtoms that you are seeing.....ie. the temperature reading pegs full scale. Try removing the sending wire from the sending unit the next time this happens and see if your gage changes. Also, hook a multimeter to the sending unit terminal and a good ground, and see what resistance the sending unit is indicating.
The link below provides resistance versus temperature for this sending unit. Hope this helps.
http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf
PS: A Wells TU-5 sending unit is said by many to provide accurate readings and be rather inexpensive (cheap). Most auto parts stores sell these.
LarryComment
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Re: 1962 Corvette Temp. Sending Unit
Could this also be a grounding issue, maybe with the gauge in the dash or elsewhere?Comment
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Re: 1962 Corvette Temp. Sending Unit
Ken:
Which one?? I think there were over a dozen charts and tables in the article.
Seems everyone today has a different specification or calibration. I guess that is part of the problem. The chart by Willcox at the end of the article I posted/linked was very close or the same as the information that you posted.
Thanks for summarizing and keeping us straight.
LarryComment
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Re: 1962 Corvette Temp. Sending Unit
Larry,
Didn't see his chart. The list I gave you is from a GM print dated 1966.
This data is used to produce the "AC Delco" reproduction temp senders.
KenComment
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Re: 1962 Corvette Temp. Sending Unit
The above resistance in ohms is lower than most of the aftermarket units I've tested. Do you know of any sending units available today that have a similar low resistance curve. (My gauge reads low so I need a sending unit with a low resistance curve.)Comment
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Re: 1962 Corvette Temp. Sending Unit
Paragon, Zip & CC all sell a sender that is correct.Comment
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Re: 1962 Corvette Temp. Sending Unit
We sell an adjustable resistor for issues like this. More info here.Comment
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Re: 1962 Corvette Temp. Sending Unit
I think what Dave said is more likely problem rather than 4 sending units (possible but). If it is wired similar to a 1960 the power comes from the iginiton switch to the guage (may be tied to fuel gauge) then gets its ground thru the sending unit(resistance). If it goes full hot I would check the wire from the sending unit to guage (bypass it see what happens).
PhilComment
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Re: 1962 Corvette Temp. Sending Unit
Another possibility is the guage contact is shorting out (ground) when it gets hot. The insulation around the guage contact could be breaking down and when it get hot it shorts to the case causing the guage to read full scale. It could then be getting ground thru the lamp base or the instrument housing. Just a thought.
PhilComment
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