1970 temperature sending unit

[D S.]

On a March built 1970 LS-5. Is it a nail head or pin head? My sending unit harness has the slip-on connector for a nail head. I was looking at another 1970 LS-5 and it had a pin head sending unit. ???

Thanks,
Scott Sims
Texas Chapter

[Jim T.]

Re: 1970 temperature sending unit

My July built 70 SB has the pin head connector on the temperature sending unit.

[Jack H.]

Re: 1970 temperature sending unit

I believe the pin head temp sender (6400759) was originally installed by the factory on 1968-71 cars and changed back to the nail head sender for '72 and later. I seem to remember a service bulletin that taught dealership mechanics to replace failed pin-head sender and cut the factory original, slip-on, barrel connector from the wiring harness and install the earlier/later side slip-on connector to agree with the replacement temp sender.

That could explain why you see some '68-71 cars configured differently. Plus, until recently, the only source for the factory orignal, pin-head, barrel connector was from surviving scrap yard cars.

The clear plastic insulation on the original connector didn't age very gracefully. Especially considering the temp sender's relocation from the intake manifold to the side of the cylinder head where heat from the exhaust manifolds tended to 'cook' it...

[Joe L.]

Re: 1970 temperature sending unit

I believe the pin head temp sender (6400759) was originally installed by the factory on 1968-71 cars and changed back to the nail head sender for '72 and later. I seem to remember a service bulletin that taught dealership mechanics to replace failed pin-head sender and cut the factory original, slip-on, barrel connector from the wiring harness and install the earlier/later side slip-on connector to agree with the replacement temp sender.

That could explain why you see some '68-71 cars configured differently. Plus, until recently, the only source for the factory orignal, pin-head, barrel connector was from surviving scrap yard cars.

The clear plastic insulation on the original connector didn't age very gracefully. Especially considering the temp sender's relocation from the intake manifold to the side of the cylinder head where heat from the exhaust manifolds tended to 'cook' it...

Jack and Scott-----


Yes, the "pin" head temp sender, GM #6400759, was definitely used for 1970 Corvettes. It was discontinued in May, 1974 and replaced by GM #546702 which was later replaced by the GM #1513321. Both of the latter senders were "button" head design and required a change of connector when used on 1956 or 68-71 applications.

In fact, the GM #6400759 is one of the few GM parts ever to be discontinued TWICE. It was first discontinued in October, 1965 but later "came back".

[D S.]

Re: 1970 temperature sending unit

Thanks to all. Now I need to swap the nail head out for the pin head. Anyone know who has the most correct harness connector to attach to the pin head sender? Apparently an owner before me installed a nail head sender with the slide-on connector.

[Jack H.]

Re: 1970 temperature sending unit

I believe Lectric Limited has re-tooled the mating connector but I can't say how accurate theirs is. If memory serves, you can buy just the connector from them to repair your existing harness...

[Warren F.]

Re: 1970 temperature sending unit

Lectric Limited is correct. I just bought the pin type connector to do just this repair.

[D S.]

Re: 1970 temperature sending unit

Thumbs down on Lectric Limited. I tried calling them and after a half-hour on hold I left a message. I then attempted to email the listed email address (sparky@wiringharness.com) and that was returned three times due to overloaded email box. Looks like Paragon has one for a lot less hassle and a real live person answers the telephone.

Thanks!

[Jeffrey S.]

Re: 1970 temperature sending unit

Also Eagle products has them. A small company and real people that know how to help. His name is Don Martin and phone number is 800-977-0030. I purchased one from them several years ago. Hope this helps.
Jeff

[D S.]

Re: 1970 temperature sending unit

Thanks, Jeff. I will contact them. I tend to gravitate toward those firms and individuals who have the best interests of the customers in mind and get items and parts to them in a timely mannner. It is absolutely rude that some individuals and firms take months or longer to get parts to their customers and never contact them to give them updates.