Temp Sending Unit
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Safety Car
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From: Indiana
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Temp Sending Unit
I have been fighting a temperature sending switch problem on my '57 for a long time. I have a 160 thermostat. It will first go up to about 190 and drop back a little, but then slowly climbs to 200 or more at idle. It is not hot though. Does not boil, no excess pressure. I used an IR gun when it shows that high but the radiator, neck and manifold at the unit read from 130 to 145 or so. Most of the 6 or 7 that I've tried all read hot, except two originals which read too cold. They may have been for a dash light. The lastest one was from Corvette Central which claims it's calibrated but it also shows hot. I have another coming from DeWitts, but it may do the same. Any ideas?
Le Mans Master
Joined: Dec 2007
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From: Puget Sound
I've gone through exactly the same thing. Tried a couple different Wells units. They read too hot. My original read too cold. Tried one from Lectric Limited (that's where DeWitt's gets theirs) it read too hot as well. It was fine for about the first 25 miles, right on 180, and then it crept up to 220, dropped back to 180 and now it's all over the place. I got tired of messing with it and put the original back in. It may read cold but at least it doesn't startle me when I glance at.
Jim
Jim
Team Owner
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Army
A really aggravating problem...especially when idling at long Orlando stoplights on a hot summer's day...your eye can't quit rolling over to look at the temp gauge and gritting your teeth. My sending unit is spot on and I'm grateful for that (verified across a range of temps with I/R gun).
I have no personal knowledge of how accurate or useful the information is in the attachment but maybe it can be used to 'match up' a temp sending unit that is at least close to correct...
I have no personal knowledge of how accurate or useful the information is in the attachment but maybe it can be used to 'match up' a temp sending unit that is at least close to correct...
Last edited by Frankie the Fink; Nov 6, 2010 at 04:03 PM.
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Safety Car
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From: Indiana
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Thanks Frankie. I have tried everyone of those in the pdf file. All too hot. The picture of the guage is from a mid year. I wonder if my gauge should have a resistor on it too? You know the 57 guage has only two terminals. The 12V side and the sending unit wire side. It's very aggrevating. Hard to drive with one eye on the guage all the time.
Team Owner
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Army
Folks will argue with this but I'll tell you what the Sea Ray manufacturer did to fix their recall on the temp sending unit in my 2001 boat reading too high. They install a resistor in the circuit until the gauge read correctly at normal running temperature. True...its a non-linear fix and the accuracy will vary around the resistor's targeted temperature but any inaccuracy hasn't been too dramatic in the boat. I'm quite satisfied with it.
Can't say if it worth trying the same thing on a classic vette tho.
Can't say if it worth trying the same thing on a classic vette tho.
Burning Brakes
Joined: Mar 2005
Posts: 1,231
Likes: 34
From: Ontario
Me Too
I had the same problem with my 66 and I tried about a dozen different new and used sending units and almost gave up. Then I was at CarQuest and asked them to look one up . They gave me 53-7719 TS6
and to my surprise it is pretty close to my IR gun.
Give it a try and if it works for you pass on the info to others.
Bill Purdy
and to my surprise it is pretty close to my IR gun.
Give it a try and if it works for you pass on the info to others.
Bill Purdy
Tech Contributor
Joined: May 2005
Posts: 15,576
Likes: 118
From: Conroe Texas
Folks will argue with this but I'll tell you what the Sea Ray manufacturer did to fix their recall on the temp sending unit in my 2001 boat reading too high. They install a resistor in the circuit until the gauge read correctly at normal running temperature. True...its a non-linear fix and the accuracy will vary around the resistor's targeted temperature but any inaccuracy hasn't been too dramatic in the boat. I'm quite satisfied with it.
Can't say if it worth trying the same thing on a classic vette tho.
Can't say if it worth trying the same thing on a classic vette tho.
Former Vendor
Joined: Jan 2000
Posts: 5,593
Likes: 631
From: Brighton
Then when you add a correct sending unit, and you have a resistor in the line, it will change it's output and provide bad readings.
If the line reading shows little to no resistance, install the new sender with anti-seaze only. Do not use pipe dope or teflon tape, as that can change the grounding of the switch body. Our switch is not made by Lectric limited and we rarely get any back.
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Verdad Gallardo
Tech Contributor
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From: Conroe Texas
I believe I've since thrown it away.
Thread Starter
Safety Car
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The first thing I would check is the resistance through the wire from the sending unit to the guage. A lot of cars have resistors buried in the wire harness somewhere to make a bad sending unit read correctly. The problem with the resistor concept is that the resistor is linear and the sending unit is not, so this will make a bad sending unit read correct at only one setting and any where else it reads wrong.
Then when you add a correct sending unit, and you have a resistor in the line, it will change it's output and provide bad readings.
If the line reading shows little to no resistance, install the new sender with anti-seaze only. Do not use pipe dope or teflon tape, as that can change the grounding of the switch body. Our switch is not made by Lectric limited and we rarely get any back.
Then when you add a correct sending unit, and you have a resistor in the line, it will change it's output and provide bad readings.
If the line reading shows little to no resistance, install the new sender with anti-seaze only. Do not use pipe dope or teflon tape, as that can change the grounding of the switch body. Our switch is not made by Lectric limited and we rarely get any back.
Thread Starter
Safety Car
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From: Indiana
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I had the same problem with my 66 and I tried about a dozen different new and used sending units and almost gave up. Then I was at CarQuest and asked them to look one up . They gave me 53-7719 TS6
and to my surprise it is pretty close to my IR gun.
Give it a try and if it works for you pass on the info to others.
Bill Purdy
and to my surprise it is pretty close to my IR gun.
Give it a try and if it works for you pass on the info to others.
Bill Purdy
Former Vendor
Joined: Jan 2000
Posts: 5,593
Likes: 631
From: Brighton
John Dingman and Christyn are running DeWitts, as I have been developing our new aluminum brazing operation for about two years now. I forward all mail I get to them. If you wanted to return the switch you could have just sent it back, we would have credited you for it. No discussion required
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From: Indiana
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Tech Contributor
Joined: May 2005
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From: Conroe Texas
Typically most places do not allow return of electrical components. Thus I wanted to discuss my issues since this correctly calibrated electrical component read 40 degrees off.
It's my mistake for not realizing I could ship it back unannounced.
I still bought another radiator from the company after that anyway, so it's not like it kept me from continued support of DeWitts.
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OK, I recieved the DeWitts unit today and installed it. I did not drive the car, but ran it in the driveway for 15-20mins. The temp came up very, very slowly and stopped just above the second mark on the gauge. I'm not sure what that temp would be. Maybe 120-130? The IR gun showed 160 on the radiator at the outlet hose, 148 on the thermostat neck and 143 at the new unit reading off the intake. Two of the originals do about the same thing. I don't think it would come up anymore if I was driving it, but maybe I'm wrong. What do you guys think?
Team Owner
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Army
Sure enough...they make a kit...nearly like the one Sea Ray used in my boat:
http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000050e~Z5 Z5Z5ABIWZ~P29.95~~~~S2XR12PPI32081182455 0g~Z5Z5Z5~Z5Z5Z50000050x#
Back when I was developing software we called this, "...putting lipstick on the pig!".
http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000050e~Z5 Z5Z5ABIWZ~P29.95~~~~S2XR12PPI32081182455 0g~Z5Z5Z5~Z5Z5Z50000050x#
Back when I was developing software we called this, "...putting lipstick on the pig!".
Le Mans Master
Joined: Dec 2007
Posts: 8,000
Likes: 659
From: Puget Sound
Thread Starter
Safety Car
Joined: May 2007
Posts: 3,678
Likes: 646
From: Indiana
2025 c3 ('68-'73) of the Year Finalist - Unmodified
2025 Corvette of the Year Finalist - Modified
2024 C1 of the Year Winner - Modified
2023 C1 of the Year Finalist - Modified
2023 C3 of the Year Finalist - Unmodified
2022 C1 of the Year Finalist - Modified
2020 C1 of the Year Finalist - Modified
2019 C1 of Year Finalist (performance mods)
2018 C1 of Year Finalist
Sure enough...they make a kit...nearly like the one Sea Ray used in my boat:
http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000050e~Z5 Z5Z5ABIWZ~P29.95~~~~S2XR12PPI32081182455 0g~Z5Z5Z5~Z5Z5Z50000050x#
Back when I was developing software we called this, "...putting lipstick on the pig!".
http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000050e~Z5 Z5Z5ABIWZ~P29.95~~~~S2XR12PPI32081182455 0g~Z5Z5Z5~Z5Z5Z50000050x#
Back when I was developing software we called this, "...putting lipstick on the pig!".
Le Mans Master
Joined: Apr 2006
Posts: 5,347
Likes: 36
From: San Clemente CA
Folks will argue with this but I'll tell you what the Sea Ray manufacturer did to fix their recall on the temp sending unit in my 2001 boat reading too high. They install a resistor in the circuit until the gauge read correctly at normal running temperature. True...its a non-linear fix and the accuracy will vary around the resistor's targeted temperature but any inaccuracy hasn't been too dramatic in the boat. I'm quite satisfied with it.
Can't say if it worth trying the same thing on a classic vette tho.
Can't say if it worth trying the same thing on a classic vette tho.
OT so I sent you a PM.
Don