AB_in_AUS

I'm a voyage of discovery on my sender unit and gauge. Does anyone know what resistance the sender unit should provide at different temperatures for a 1979.

I suspect I have a double whammy .. both the sender unit and gauge. We tested the gauge and it is reading high but I have no reference points on the sender unit.

One of the complications I have is mine is an early 79 and I have found a number of 78 parts(guess they were left over in the parts bin).

Any thoughts greatly appreciated.

0Willcox Corvette

I have this info, but I'm out of town and don't have access to it at the moment. I'll see if I can post it up later tonight.

AB_in_AUS

that would be great. Really appreciate it

JimLentz

http://willcoxcorvette.com/instructi...Revised_R3.pdf

AB_in_AUS

hi Jim, Thx

I was trying to track down the resistance the sender unit should provide at different temperatures for a 1979. Wilcox had provided the required ohms at the gauge for a 79

0Willcox Corvette

Hi Jim-


For some reason, I skipped over 78 and 79. I arrived home this morning, but I've not had a chance to dig up what he needs.

Let me take a look in a few minutes.

Willcox

0Willcox Corvette

Temp or gauge mark first, required ohms second.

100 - 315
1st mark - 119
220 - 89
2nd mark 61
middle of orange 44
280 39

AB_in_AUS

Thx, do you have any info on the sender unit? eg like the article at:

http://www.lbfun.com/warehouse/tech_...g%20gauges.pdf

what had the following detail for a "typical" sender unit

Temp Resistance
100 410
110 355
120 300
130 240
140 187
150 171
160 150
170 134
180 123
190 112
200 94
210 83.5
211 83.0

I asked Lectric Limited but they said "We do not release the operating specs. for the sending units. The specs. are proprietary information."

At the gauge, I have been experimenting and the data I have at the moment (its not 100% accurate as I made the mistake of ordering a 1 turn potentiometer and am waiting on a 10 turn to be more accurate) is

Temp or Mark Req Ohms Observed Ohms
100 315 440
1st Mark 119 150
220 89 92
2nd Mark 61 63
280 39 44

What I'm struggling with is probably three questions:

1. What should the resistance at the sender unit (if working correctly) be at 160 degrees?
2. What should the resistance at the sender unit (if working correctly) be at 180 degrees?
3. What would the temperature be at 119 ohms resistance ie the 1st mark (if the gauge is working correctly)?

That's what I know at the moment, any thoughts greatly appreciated.

0Willcox Corvette

Temp or gauge mark first, required ohms second.

100 - 315
1st mark - 119
220 - 89
2nd mark 61
middle of orange 44
280 39

This scale.. it is the required input to make the dash unit operate correctly IMHO.

The inputs were derived from testing original NOS gauges, Original used gauges and compiling date over and over. This issue at hand can all go away by installing an adjustable resistor. You can then match your dash unit to the sender.

As you can see.. your sample data is close to mine. My data is what I use to calibrate with Period! And while data can be different per each particular gauge, I afraid my friend you suffer from the same OCD issue I have... lol

What you'll see in testing is the lower the temp the higher the variance. The higher the temp the less margin for error or tighter variance. Make sense (god I hope not).. lol

Willcox...

0Willcox Corvette

I have plenty of info on the sender unit.. and all the reproductions have issues. Buns did some testing that came to the same conclusion. The repro sender is not going to work correctly and if it does you are one lucky person. Since no one knows exactly for sure where the 180 mark is on the actual gauge, it would be hard to make that assessment. Considering the 1979 dash unit was designed to show you where 220 was (approaching an issue). I can figure this out for you if needed, but I never felt it was that important on the 1979 gauge to know where 180 was. Most 1979 cars run hotter than 180 all the time.

I swear you're gonna make me have nightmares tonight over-thinking this again. . . .

If you are testing, get yourself a 10 or 15 turn pot and have at it.. If your dash unit is working at 220 (aprox. 89 ohms) then 180 should be fine as well. I would concentrate on the first mark, 220 and the second mark before I worried about anything else.. you get those close and you'll be fine.

Willcox

AB_in_AUS

Brilliant, Thx

PS: You're pretty close re OCD

0Willcox Corvette

Have you seen this thread?
https://www.corvetteforum.com/forums...willcox-d.html

I've worked on this for over a year.. this is the answer to any dash to sender issue. and yes, my ocd is hurting right now.

This resistor creates a linear change to a non linear gauge.. Pretty swank I might add.

Willcox

AB_in_AUS

thx, I'll have a read