need smaller temp sender for 71

[71roadster]

I need a 3/8 npt temp sender that will work with my factory 71 gauge. The stock one is 1/2 npt and my new heads have 3/8 npt hole and I dont want to enlarge the hole or use an adapter. Anyone got any ideas? The late model sender I got at the local autoparts store doesn't seem to register and I verified the gauge is working.

Thanks
Chris

 

[Dave L.]

H20 sensor.

I focused on this problem for another member about 2 years ago.
I tried about 5 different senders with no luck. The resistance values are much higher for the newer senders with the 3/8pt. This will cause the guage to read incorrect(not even close!). The only solution was using a combination of adapters with the original sender. I believe I have one laying around here somewhere,but it sticks out quite a bit and it is not pretty.

Dave

p.s.your best bet is to drill and tap that hole.I know it is not what you wanted to hear.

 

[JohnZ]

AutoMeter makes 3/8" NPT temp sending units (also 1/8" and 1/4" NPT).

 

[71roadster]

autometer

But do the Autometer sending units work with our whacky gauges?


Will run sender in manifold until I get a solution that works in the head.

Chris

 

[Dave L.]

Chris - before you purchase any sender from "Autometer" or anyone else,make sure to compare the resistance value from your original to the one you are considering.Good Luck..

Dave

 

[Jack]

I need a 3/8 npt temp sender that will work with my factory 71 gauge. The stock one is 1/2 npt and my new heads have 3/8 npt hole and I dont want to enlarge the hole or use an adapter. Anyone got any ideas? The late model sender I got at the local autoparts store doesn't seem to register and I verified the gauge is working. Thanks Chris

Chris I haven't tried this ... yet. But I may be able to help. I have some updated cross-references w/ specs. I'd need GM p/n for your old 1/2 sender ... or resistance values ... both would be ideal. Though I too have a 71 ... I don't have that OE info. May be the same path Burglar's already reconned ... but I'll try if you can forward info.
JACK:gap

 

[Dave L.]

The sender part# is 1513321. I will have to review all my notes at work on the resistance values on all the senders I tested. The resistance values on the newer 3/8pt senders are much greater than the original.

Dave

 

[MaineShark]

If you can find out the resistance specs of each, say at room temp, and also when hot (put each in boiling water, since it will be exactly 212 degrees), it shouldn't be much trouble to wire up a converter. If someone has the numbers for the stock sender, and whichever sender they want to use instead, I can dig up my old electrical engineering notes, and see how much I remember

Joe

 

[Jack]

The sender part# is 1513321. Dave

According to 2002 Standard Motor Products (aka standard ignition) parts guide ... 1513321 gauge sender crosses to Standard's pn TS-6. TS-6 is 1/2"-14 gauge sender for 79-60 chevy. Further TS-6 specs are 368 ohms closed at 100F ... and ... 80 ohms open at 220F.

Sadly, my smp book does not show a 3/8"-18 sender with resistance specs anywhere near those of TS-6.

Maybe another brand such as Autometer has a 3/8 sender with matched impedance specs?

I'm no EE ... but it seems that a series of "impedance-matching resistors?" could be wired-in at input to gauge ... then use a sender with lower resistance specs. Such as Standard's pn TS-58. According to same reference, TS-58 is 3/8"-18 gauge sender for 97-69 ford. Further TS-58 specs are 176 ohms closed at 100F ... and ... 24.1 ohms open at 220F. Standard's gauge sender pn TS-24 is similar ... 71-65 ford ... 125 ohms closed at 100F ... and ... 17.12 ohms open at 220F. Seems like you'd wanna try to match impedance at 220F. Maybe Dave or Joe will advise if this approach might work ... I dunno?
JACK:gap

 

[MaineShark]

Well, those numbers give us:

TS-6
Offset = 608 (ohms)
Rate = -2.40 (ohms/degree)

TS-58
Offset = 303 (ohms)
Rate = -1.27 (ohms/degree)

TS-24
Offset = 215 (ohms)
Rate = -0.899 (ohms/degree)

You're correct that some resistance will need to be added, in series. That will correct the difference in offsets. So, for example, the TS-58 will need 305 ohms added to correct the offset. The rate need to be nearly doubled, though, and I'm trying to remember how to set things up to multiply a resistance. I know it should be possible, but it's been a few years, so it may be a while before I remember what I'm looking for.

In either case, the offset resistor, and some other resistor in the system, should be asjustable. For one, I'm sure you'll never find exactly the correct resistance (305 ohms isn't a standard size), and it will also allow you to adjust it to read accurately, since each sender and guage are slightly different (manufacturing tolerances). Putting in the "wrong" sender might give you a more accurate reading

Of course, the other option is to buy a new guage that will work with a modern sender, and take the face off, then fit the face from your old guage onto the new movement. In all honesty, that might prove to be the most reliable way to do it.

Joe

 

[71roadster]

volvo sender

I found that the stock sender has impedence of 72 - 88 ohms at 220 degrees. Looked thru a parts book for a while and found that Volvo's used for almost 40 years a 3/8 npt sender that is 64 - 76 ohms at 220 degrees. It is part number WT510. Unfortunately I could not find that sender at the 2 parts places I went to and the 3 I scrounged up from the junkyard over the weekend were all 1/4 npt and about 35 ohms at 212. So I'll keep looking for the correct one. Thanks for all your help.


Chris

 

[Dave L.]

Chris - keep us updated on your problem. I wish I had an easy fix for you. If you do find a sender that will work off another vehicle I'd like to know for my future reference.

Dave