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Temperature sending unit help


66Lincoupe

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I am building a 1964 with my daughter. It is a basket-case, but solid since it is a desert car. The only issue is that EVERY plastic piece is gone since the car sat outside for years. I am rewiring the car and need to know which terminal on the temperature sending unit has the dark green wire and which has the light green wire. I am using an aftermarket kit, but since the kit is GM based all of the colors are there and correct for function. The original wires were near the sender but didn't have any insulation left or a connector. Ideally I would LOVE a photo of a sender with an OEM connector that shows the wire colors. I am trying to keep as much of the original function as possible.

 

I've had no luck contacting BWD getting specs on the sender, either. Does anyone happen to know the cold operating range of the sender? If I remember right the last car I had with a cold light wouldn't light the lamp unless the coolant was colder than 70 degrees - and living in the desert the average temp in my shop is still in the mid 80s so I show no continuity on either terminal at 80 degrees so I am turning to you all for a bit of help!

 

Thanks!

 

Helping the next generation keep the passion for hot-rods...

 

wiringwithmygirl.jpg

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Thanks for introducing another youngster to old cars.  Excellent!

 

OK, two parts to your question answered below:

1) When you look at the temperature switch connector from above, it forms the shape of a capital "L".  The connector that forms the upright part of the L is for the "cold light" (dark green wire on a '63).  When the engine is cold, this tab is grounded.  The cold temp light bulb has power all the time and is seeking a ground.  It gets it here.  The tab that forms the base of the L is for the "hot light" (yellow wire on a '63).  Same deal, it provides a ground to the hot light bulb.  I can send you a photo if you want.

 

2) The 1963 Buick Shop Manual says that the cold light comes on when it is below 110 deg. F.  That is consistent with my experience.  In Houston, where it gets quite hot, my cold light is on when I first start a cold engine.  It does not stay on long!

 

Hope this helps.

 

BTW, the two terminals on the switch will never have continuity between them for a properly functioning switch.

 

 

Edited by Jim Cannon (see edit history)
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You can always toss the sender in the freezer or warm oven for a sanity check.  Ice water and a torch/lighter would be quicker, but...

 

If you painted the engine without the sender in place (or wrapped it in teflon tape), you might not have any continuity between the sender and the block.

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  • 3 weeks later...

Sorry it took so long to reply... Forgot my password and then just got busy!! Thank you for all of your help. Looks like we got a bum temp sender. The new-new one seems to work correctly. '63 and '64 have a different color code according to the wiring diagram I have for '64 and the input you all offered, but the sensor is the same, so on '64 a dark green wire is hot instead of yellow, and a light green wire is for cold...

 

thank you again!! On to the next step in this adventure...

Edited by 66Lincoupe
forgot to add something (see edit history)
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From alini's post it looks like '65 has a green and yellow wire as well (I'm color blind so this is really fun, lol) But here is a crop of the wiring diagram I have for '64 which, according to my wife, is correct for the car we're working on since there was a light green and light green wire in the vicinity of the TSU on our car... 

 

TSU.jpg

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15 hours ago, alini said:

Mine are dark green and light green

 

:) color blind... I should get a handicap spot, lol. The light one looked yellow. Thank you!

 

I am an engineer and deal with wiring every day... I usually end up ringing stuff out to make sure I have the correct wires - I knew I had the dash wired correctly and what the wires did but not which connector on the TSU. While the wiring will not be stock I want anyone working on it in the future to be able to grab a wiring diagram and have it be fairly accurate. 

 

 

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  • 2 months later...

Getting closer. After unpacking the front and rear glass we found that the previous owner gave us the wrong parts. We ended up with a windshield for a 67-72 Chevy truck. She sold that off and got the correct windshield installed. All of the chrome has been Scotchbrite scuffed or bead blasted so we are looking for replacements or somewhere to have the stainless re-polished and the chrome re-chromed and replacements for the bent and broken stuff... But she's driving it now and happy as can be.

 

RivieraRunning.thumb.jpg.9261f42de302cca1e45bf4df69659fb3.jpg

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