My parts stores keep trying to sell me a temperature sending unit that is too small for the hole. I just had the engine rebuilt, so there was just a plug in the head by the thermostat. I assume this is the correct location, but now I'm second guessing myself since the sending unit is too small. I have a shop manual, but there is no good picture or description, so I guess I just have to ask.

Thanks,
Dave

hello,
take the plug with you on your next visit to the parts place as a sample.
you will probably find that adapters are available,to put into the thermo housing then screw the small sender into that.
they might have the correct sender somewhere if you have a sample thread to show.
we have adapter fittings in Oz anyway.
good luck.


regards,Rod

Looking up 1976 plymouth volare at rockauto.com shows me ACDELCO Part # U1850 for the smaller 1/8" npt unit and STANDARD MOTOR PRODUCTS Part # TX11 for the larger (3/8" ?) unit. Should be good enough for local parts store to cross reference if you don't want to mail order.

Adapters do work but you may see a few deg. drop with one. Don't replace one sensor for another unles someone can confirm they both have the same output curve.

Pierre wrote: hello Pierre,
whilst I do'nt doubt what you say,how could the sender read a lesser temperature?. the centre probe of the sender is in the coolant exactly the same as without an adaptor.
I could see it happening if the adaptor had to transfer the temperature,but its only role is (apart from adapting the thread size) to provide the electrical connection (earth or ground) to the thermostat housing.
am I missing something here? comments from the electricians please.

regards,Rod

The sender is grounded through the head and an adapter might have a little added resistance.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

might or does? different metals (brass) the cause.?
as a matter of interest,I did some checking with a sender and adapter and a old slant head on the bench tonight,and cannot detect any difference in resistance sender to head with or without adaptor.
Myth "busted" or no? (apologies to Mythbusters"


Rod

I said "might" because it depends on how clean the threads are when putting the adpter in and whether or not sealing compound or tape are used. It was more of a theoretical observation than one borne of experience. My instinct tells me that ti would be preferable to get the correct sender but if it can't be found then one has little choice.

Reminds me of a joke: Two young boys were sitting on a street corner and one said to the other "My instincts tell me it's going to rain." The other lad says: "Your what?" His companion replied: "My instincts.... they tell me it's going to rain." The other youngster replied: "My end stinks too but it don't tell me nothin'."

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

O.K, the jury is still out then,but their decision will have no impact on the sentence of the accused. (the sender)
so long as it reads consistently,all will be well.

Rod

Hello,
Last summer I posted the comparison of resistance vs. temp for the Ford temp gage that fits right in the big hole vs. the Mopar one for little hole and big hole. Essentially no difference in the critical temp ranges.

I was concerned with effect of resistance vs. temp of probe metals since resistance is what works the gage (besides the signal to gage) I don't remember the variances but they were in the third decimal place...essentially a direct swap. I think the Ford one was for the 351 but look in the Search for the post, probably about July.

rock
'64d100

Adaptors don't cause problems with the temp gauge reading as long as they're made out of metal and you're reasonably careful to clean the threads in the head. The main thing to watch out for is that the '60-'63 sender has a different resistance range than the sender they started using in '64, and there might've been another change or two in resistance range in the early and mid '70s.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I guess it depends on the adapter itself. Those adapters don't sink into the threaded hole as far as you may want them to. As long as you can do it with a single adapter you should be ok.

Dan - thanks for confirming there are different curves, thats what I was afraid of.

The "large thread" (1/4 NPT) temp sending units were used on 60-62 (and some 63) SL6 engines. What year / application is your parts man searching for?
DD

Hi guys,

Adapter or not, what counts is the temperature of the water touching the sensor...on sensors too short to fully enter the fluid, the fluid doesn't circulate properly, it remains as a relatively static pool around the sensor. The curves I measured varied, but largely in the range below 150 degrees....interesting phenomena showing alloy differences, but of little practical import. It was easy enough calculate rate of change for any measured time interval (mine were 5 sec) but so long as the slopes are roughly the same, again it doesn't matter. This means "yes" the curves are different, but the difference is of no import. However, the sensors are different lengths and this is an area where longer is better.

The practical result is I took the forum advice, drilled and tapped the thermstat housing and inserted the sensor there. I wired a temp light to the original little sensor just to have a redundancy check against the gage with temp numbers on it.

rock
'64d100

Mmm...no, the difference actually matters.

The '60-'63 sender with the flat slide-on terminal has the following specs:

Thread Size: 1/4"-18 NPT
12.5Ω @ 220°F

The '64-up sender with the round push-on terminal has the following specs:

Thread Size: 1/8"-27 NPT
17.1Ω @ 220°F

Using the early sender with a late gauge will cause the gauge to read higher than it should.

Using the late sender with an early gauge will cause the gauge to read lower than it should.

There are senders available in the early size with the late resistance value, and vice versa, for solving this problem when doing a cylinder head swap across the year boundary.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan,

Maybe that is why my gauge is always reading low. I have a 78 head with the large 3/8 sender hole. I bought a brass adapter and cut off the extra threads so the small sender probe they sold me would stick out into the water flow. Used some teflon pipe thread sealant (comes in a tube) and never thought about it until now. My 1974 temp gauge always reads low.

Did they go to another 3/8" sender for the 78 and on peanut plug heads?

_________________
Aggressive Ted

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