Replacement Cylinder Head Temp Gauge

[Jake]

I know this has been covered but do yopu guys have a recommendation for an aftermarket cylinder head temp gauge for a Corsa?

I've got the instrument cluster out and though the one I have has worked alright, I think I'd like to find a good new one, especially since I installed the new VairTrix Thermistor.

So is there a go-to new gauge that'll fit in the stock dash?

[66vairguy]

I know this has been covered but do yopu guys have a recommendation for an aftermarket cylinder head temp gauge for a Corsa?

I've got the instrument cluster out and though the one I have has worked alright, I think I'd like to find a good new one, especially since I installed the new VairTrix Thermistor.

So is there a go-to new gauge that'll fit in the stock dash?

Jake --- the Corsa (DELCO) thermistor and gauge are UNIQUE. The Vairtrix was designed to drive the Corsa gauge, NOT ANY OTHER GAUGE! Most after market gauges are designed to work with thermocouples. Years ago I looked into this and only Piper Aircraft used the (DELCO) head thermistor. What did Piper owners do if the gauge indicated incorrectly -- only one thing allowed - install a newer gauge AND sender made by a different company as NOBODY makes replacement parts equal to the the ones DELCO stopped making.

What to do ---- years ago I bought a dozen used gauges to "characterize" them and only one was WAY off! I ended up building my own gauge driver box using a thermal couple, but just as I finished Vairtrix came out with their product for less money. I like my setup (of course ) since it has a display on the box and is located away from engine heat.

Anyway ---- used Corsa temperagure gauges are not hard to find so WHY do you want to replace it if you have a Vairtrix driver???

[Jake]

only reason I was thinking about something new was because all the used ones I've looked at have looked pretty rough and after all the work I've put into redoing my dash I'd like to put in something clean.
I'll be pretty happy with mine as long as it works okay.

I should be putting the dash back into the car this weekend, at least I really want to find the time to finally get the car put back together and on the road now that its warming up a little here in Boston.
I mean theres a high of 48 tomorrow here!

[66vairguy]

only reason I was thinking about something new was because all the used ones I've looked at have looked pretty rough and after all the work I've put into redoing my dash I'd like to put in something clean.
I'll be pretty happy with mine as long as it works okay.

I should be putting the dash back into the car this weekend, at least I really want to find the time to finally get the car put back together and on the road now that its warming up a little here in Boston.
I mean theres a high of 48 tomorrow here!

By "clean" do you mean the dial face, or the clear lens? The lens, if not fractured, cleans up with the small "Turtle Wax lens restorer kit". See https://www.ebay.com/sch/i.html?_nkw=tu ... 58439177b3

The kit is small, with pads and polish to do by hand, perfect for small instrument lens.

If you can't find a temp gauge with a good dial, PM me as I might have one.

[Jake]

My lenses are pretty perfect. The dial face isnt perfect, but really its okay.

I'm starting to fall into the dreaded "perfectionist" stage of working on my car. Where I'm trying to improve everything I touch!

Which isn't really my goal for this car, so really I'm probably all set.
Though I appreciate the offer and will keep it in mind.

[66vairguy]

My lenses are pretty perfect. The dial face isnt perfect, but really its okay.

I'm starting to fall into the dreaded "perfectionist" stage of working on my car. Where I'm trying to improve everything I touch!

Which isn't really my goal for this car, so really I'm probably all set.
Though I appreciate the offer and will keep it in mind.

Yes I know about "overdoing it" and sometimes have to remind myself that my car is a driver and say "good enough". Fact is most folks don't notice the little stuff that isn't as good as it could be. After fixing some of the poor workmanship from the factory, I can't complain about my work. Good luck with the car and enjoy.

[isucorvair]

You probably want stock...but I'm really happy with the SpeedHut cylinder head temp gage. Face is very customizable, can be configured to look (almost) like a stock gage, if you didnt know better.

Eric P.
DeWitt, IA

[vairchet]

Probably have a dozen of these. Roughly 3/4 of them no longer function correctly. Like many other electrical (or mechanical) dash components that I've collected over the decades, if it doesn't work, it gets tossed.

[66vairguy]

You probably want stock...but I'm really happy with the SpeedHut cylinder head temp gage. Face is very customizable, can be configured to look (almost) like a stock gage, if you didnt know better.

Eric P.
DeWitt, IA

I bet the SpeedHut unit has it's own sender for their gauge Most units now are thermal couple, but if they are not "Cold Junction Compensated" they are not very accurate. That was the old VDO gauge for VW's problem. A shame VDO didn't upgrade the electronics, they just stopped making the gauge and sender when folks complained.

Jake already has a VairTrix sender and working gauge, but if he wants to spend the money for a different look, then it's his decision.

[66vairguy]

Probably have a dozen of these. Roughly 3/4 of them no longer function correctly. Like many other electrical (or mechanical) dash components that I've collected over the decades, if it doesn't work, it gets tossed.

'65 - '66 Corsa Temperature Gauge.jpg

The clocks always quit, new quarts works well. I install another temperature gauge in the clock position so I can read each head.

Often the temp gauge can be fixed by cleaning up the rear connections and the wire wound resistor. If the resistor is badly corroded then it is probably no good.

If I wasn't winding down my Corvair stuff I'd take them and test them.

[Jake]

You probably want stock...but I'm really happy with the SpeedHut cylinder head temp gage. Face is very customizable, can be configured to look (almost) like a stock gage, if you didnt know better.

Eric P.
DeWitt, IA

I bet the SpeedHut unit has it's own sender for their gauge Most units now are thermal couple, but if they are not "Cold Junction Compensated" they are not very accurate. That was the old VDO gauge for VW's problem. A shame VDO didn't upgrade the electronics, they just stopped making the gauge and sender when folks complained.

Jake already has a VairTrix sender and working gauge, but if he wants to spend the money for a different look, then it's his decision.

I actually really want a very stock look.
And I'l live with the one I have, its just the usual slightly pitted not perfect 60 year old gauge.
If there was a stock looking, new product that worked with the VairTrix thermistor I'd be all over it but absent that , this one will do.

[67monza]

I ended up building my own gauge driver box using a thermal couple

I'm curious to see what you did. I also built a gauge driver for a thermocouple.

[66vairguy]

I ended up building my own gauge driver box using a thermal couple

I'm curious to see what you did. I also built a gauge driver for a thermocouple.

If one wanted to build 1,000 units it pays to get custom chips made up. For just a few units I used off the shelf chips that work with the Arduino nano board and used C++ code. I wanted a digital readout on the box to check against the gauge for accuracy. There are different ways to drive the gauge, but to keep the power and heat down I used modulated pulse width that allowed me to "customize" the response to drive the gauge. The stock gauge response doesn't match the thermistor non linear response as well as it should. Granted the small temperature gauges are not easy to read so accuracy resolution isn't great, but I used a customized look up table to improve accuracy. Anyway --- I have time to tinker and need to keep my old skills up. Note - for it's time the engineers did a fantastic job with the thermistor and gauge to make a low cost setup. Yes new replacement thermistors could be made, but when I looked into it the cost was beyond what the average Corvair person would want to pay, not to mention they drift out of spec as time and thermal cycles accumulate.

I have no idea what VairTrix did, but it is obviously simpler and less expensive vs. the way I did it. Vairtrix doesn't publish specifications, but folks seem to be happy with their product. I read on the old forum Vairtrix stopped making their temperature gauge driver due to low demand and sold all remaining units to Clark's - JUST WHAT WAS POSTED and I cannot confirm this!!

[67monza]

Arduino nano

Very cool. I went much more old-school. Op-amp, npn transistor, voltage regulator, assorted resistors. I need to start playing with the newer tech.

[66vairguy]

Arduino nano

Very cool. I went much more old-school. Op-amp, npn transistor, voltage regulator, assorted resistors. I need to start playing with the newer tech.

I thought about going with small thermistor chip and using an amplier, but I could not find a good cross reference for the original A/C Delco thermistor "slug" and characterizing the curve takes some work, not to mention all the old original thermistors tend to be off a little. I DID characterize a dozen temperature gauges and discovered the curve did not exactly match the thermistore (the gauge curve has a "bump" in the middle).

Note the old chart from CORSA was done with a thermistor that was PASSIVE measurement, so it is off some. The Corvair thermistor has to conduct a relatively large amperage to drive the gauge (by todays low power standards) so the "slug" was fairly large (by today's standards) and when a thermistor conducts amperage it "SELF HEATS" and YES the engineers allowed for that. When you test a thermistor you have to apply that amperage to get the correct resistance per heating. I found the amperage figure in an A/C DELCO drawing of the thermistor. Anyway ---- the passive curve (heat up thermistor and measure resistance) is not valid as no amperage is applied like when it is hooked to a gauge!!! A shame and I did write the folks who measured the resistance curve vs. temperature to redo the test with a real gauge, but I never got a reply.

[67monza]

characterizing the curve ... thermistor conducts amperage it "SELF HEATS"

Indeed, it's a nightmare. My middle indication is good, but the rest is a mess. I just ordered some arduino nano boards. Long overdue to start playing with those.