Spyder/Corsa Cylinder Head Temp Gauge Thermistor

[lonestranger]

What solution(if any), have the group came to, relative to replacement for the above listed Thermistor - (the one in the left head of turbo cars, that operates the cylinder head temp gauge - not the other thermistor that drives the idiot light). It is the "little sparkplug" looking sender. They apparently have not been available from GM, or Clarks for some time. Clarks has a listing for a cylinder head temp sender, but it apparently is for aftermarket gauge (sender fits under a sparkplug, according to Clark catalog. Anyone have solution, or possible a stash of the original thermistors?

[Scott V]

there is only 1 thermistor on sypder/corsa - thats on the left head & operates the head temp gauge. the 1 on the right side that drives the idiot lite is a snap switch.

no new *repop* thermistors are available right now. used ones are out there.

-Scott V.

[bbodie52]

There are a pair of 1965-66 Turbo heads for sale on eBay that need a lot of work. Can't tell from the pictureas if the thermister is present in the head or not, but you might contact the seller to find out. Currently 1 bid for $50. If this lead fails to pan out, you might watch for used 140hp or turbo heads to see if you can find a cheap head with the thermistor still in place. Since Clark's would charge $295 if they had thermistors, a used head with one in it might be the way to get one.

http://www.ebay.com/itm/65-corvair-cors ... 89&vxp=mtr

ATTENTION!

Starr Cooke has a thermistor for sale for $85 on eBay!

http://www.ebay.com/itm/Corvair-Spyder- ... 72&vxp=mtr

eBay Item No: 111050813810

1 available / 2 sold

Rare Corvair Hi-Po clyender head temp guare sending unit off Turbo and 140 HP Corsa motors. Tested with an Ohm meter and it is perfect. Has brass sealing ring and threads have been chased. Shipping lower 48 only 5.00

[Scott H]

I have a friend who has a couple for sale. He wants $100.00 each.

[miniman82]

I have a pair, paid $100 each as that seems to be the going rate for a good one. No repops, salvage and NOS only. I plan to run dual gauges, one for each side of the engine.

[LBC TITAN]

Hello Lonestranger,

I'm not sure if you've solved your problem by now as this is an old post. I'm having the same issue with the thermistor and will be trying the following.

Copied from:
http://flycorvair.net/2013/10/15/cylind ... asurement/" onclick="window.open(this.href);return false;

An easy way to put CHT here is to use a 10MM spark plug ring CHT terminal and hold it down with a 5/8″ long bolt with a washer. This will work great. All Corvairs with the exception of ‘Spider’ and ‘Corsa’ high performance models had an idiot light in the dash that was tripped at 575F by a sender screwed into this hole. I had a guy who had never owned a Corvair tell me that the 10mm ring would not work because “it needed to touch the bottom of the hole” Really? the GM sending unit didn’t, and it read just the same.

What solution(if any), have the group came to, relative to replacement for the above listed Thermistor - (the one in the left head of turbo cars, that operates the cylinder head temp gauge - not the other thermistor that drives the idiot light). It is the "little sparkplug" looking sender. They apparently have not been available from GM, or Clarks for some time. Clarks has a listing for a cylinder head temp sender, but it apparently is for aftermarket gauge (sender fits under a sparkplug, according to Clark catalog. Anyone have solution, or possible a stash of the original thermistors?

[lonestranger]

Unfortunately, I have still not solved the question of the non-operative CHT gauge. This is after 3 different thermistors (used of course), 2 different dash gauges, and a completely new wiring harness (Engine Comp, Chassis and Dash Harnesses! So for the time being, I have moved on to other projects on the Spyder. Complete new braking system w/dual MC and stainless steel brake lines, F/B Turbo w/ late YH, and the latest project was converting to a 63 amp internal reg alternator system. I might point out that my corvairs (and my Jaguar XKR) are my therapy, in that they,are my Golf! I read with interest the article on CHT gauges etc in the Fly Corvair .com issue. When I get back to the Spyder, that will in all likelihood be the next project. Charles, I do thank you for thinking of me with the mention of the article.

[Nickshu]

They are around. I bought an NOS one in the original box for about $325 last year. I see used good ones going for $100-200. Watch eBay and/or ask on the forums.

[LBC TITAN]

Why buy somebody's used Thermistor, you don't know what you gonna get, and with no guarantee? The technology is from the 60's, why not upgrade to something more up to date like the Westach Dual CHT Gauge with thermocouple for the amount of money you're going to spend.

http://www.westach.com/gauge_images/2DC8.jpg" onclick="window.open(this.href);return false;

[azdave]

Why buy somebody's used Thermistor, you don't know what you gonna get, and with no guarantee?

Many people prefer using the original instruments and enjoy the challenges of keeping them operational. Sometimes that is a lot of work but it also can be very rewarding.

[BobWitt]

You should test the gauge and sensor! To test the gauge i used a potentiometer from Radio Shack (0-1000 Ohm, 0.75 watt, 15-turn) and tested, and validated the temp gauge!



What follows is the Resistance to Temp curve. Set the pot at 450 ohms and the gauge should be at 300 Deg F, 250 ohms and the gauge should read 400 Deg F... Put the Thermister in the oven at 300 for 20 minutes - it should read 450 ohms, etc.. If all that is correct - what is left is wiring, connections and ground plain... Dash must have good ground to body, body to engine, engine and body to battery negative (and of course sensor to head!)... Put all of this together and it will work!

Good luck with your project!

[recessbilly]

A proper alternative, perhaps. Are threads 3/8-24?
http://www.aircraftspruce.com/catalog/i ... ochcht.php

[BobWitt]

Interesting - I have requested the characteristic curve and current carrying capabilities if this sensor. I don't know the thread size of the oe sensor. I only have the one and it.is.in my head. Maybe someone else could provide this.

[azdave]

A proper alternative, perhaps. Are threads 3/8-24?
http://www.aircraftspruce.com/catalog/i ... ochcht.php

Detail info about trying to use the Rochester probe;
http://corvaircenter.com/phorum/read.ph ... 164,page=2

[bbodie52]

ROCHESTER 3080-38 TEMPERATURE PROBE
3/8-24 NF3 250-550F
http://www.aircraftspruce.com/catalog/i ... ochcht.php
Part # 3080-38




http://corvaircenter.com/phorum/read.ph ... 164,792859

Re: Cylinder Head Temp Gauge installation notes
Posted by: Allan Lacki
Date: May 20, 2014 05:35AM

Regarding AC Delco thermistors and aircraft: The AC Delco Part Number for the Corvair thermistor was 1513431. Beechcraft’s parts catalog shows Part Number 1513431 for a cylinder head temperature sender unit. And, back in the day, Beechcraft installed AC Delco gauges in their planes. Could this be the same as the thermistor GM installed in Spyders and Corsas? The question may be academic, for it appears the Beechcraft version is just as rare as the Corvair version! AC Delco got out of the business of selling aircraft gauges about thirty years ago.

A MacGyver alternative: Aircraft parts houses also list a "Rochester 3080-38" thermistor which has the same dimensions and thread pitch as the Corvair thermistor. The temperature range is 250 to 550 degrees Fahrenheit, which is about right for a Corvair engine. Prices range between $75 and $150 apiece, depending on the parts house.

However, the Rochester thermistor has a resistance-to-temperature curve that is different from that of the Corvair thermistor. It is not intended to be used with AC Delco cylinder head temperature gauges. It is supposed to be used with Rochester cylinder head temperature gauges instead. (Rochester makes a complete line of gauges for small aircraft). Perhaps a good electronics geek could engineer a simple circuit that would make the Rochester 3080-38 thermistor compatible with the Spyder/Corsa gauge.

By the way, the Rochester components are manufactured by Rochester Gauges of Dallas Texas, which is NOT the General Motors subsidiary that made Rochester carbs!

Attached is a drawing of the Rochester 3080-38 thermistor.

[LBC TITAN]

Please let us know what you find, this is an interesting topic and will benefit all Corvair drivers with this issue. I have to change my valve cover gaskets next week, I will get you the thread size then. Maybe someone will beat me to the punch by next week.

Interesting - I have requested the characteristic curve and current carrying capabilities if this sensor. I don't know the thread size of the oe sensor. I only have the one and it.is.in my head. Maybe someone else could provide this.