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VairTrix CHT sensor problems?
Posted by: alphasud ()
Date: October 21, 2020 07:47PM

I installed a VHT-100 on a EM back in the spring. I had to relocated the electronics module initially because where I placed it it was getting too hot. Now when you turn on the ignition the CHT gauge pegs and then drops back to 200 degrees. I also checked the grounding to the gauge. 2 emails to the company last week have gone unanswered and I did receive email confirmation from the site. Anyone in the forum run into a similar issue?

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
1965 Corsa mid engine project
1973 Mercedes 280 project

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Re: VairTrix CHT sensor problems?
Posted by: cnicol ()
Date: October 22, 2020 06:42AM

Isn't that the built-in, key-on self test? I have no personal experience but I remember reading about that feature.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: VairTrix CHT sensor problems?
Posted by: toms73novass ()
Date: October 22, 2020 08:12AM

Mine "pegs" on startup for self test.

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block (Sold)
86' BMW 325es
98' VW Jetta TDI, for daughter
01' Audi Allroad Stage 3 twin turbo
67' UltraVan 211 "Violet"
NFCC, UMCC
Grand Island, NY

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Re: VairTrix CHT sensor problems?
Posted by: azdave ()
Date: October 22, 2020 09:37AM

cnicol Wrote:
-------------------------------------------------------
> Isn't that the built-in, key-on self test?

The self-test on the LM Corsa gauge that I saw takes the needle to 400F (mid-scale) and then back to actual readings. It did not peg the needle to max temp. Not sure if all version do that.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5






Edited 1 time(s). Last edit at 10/22/2020 09:38AM by azdave.

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Re: VairTrix CHT sensor problems?
Posted by: Spectre ()
Date: October 22, 2020 10:20AM

While From the Vairtrix website:

When starting your vehicle, the CHT-100 performs a self-test procedure by checking for an open or shorted sensor. It then moves the needle briefly to 400 degrees (center dial). When you see this activity, you can be confident your head cylinder temperatures are being measured and reported accurately.

More information: [vairtrix.com]

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: VairTrix CHT sensor problems?
Posted by: Grandpacorvair ()
Date: October 22, 2020 10:33AM

I suspect your VHT-100 has an issue... According to the website it should initialize by going to 400° and then return to the actual temperature. The one on my Spyder does this.

According to the website the unit has a one year warranty. It says to return the unit, along with a copy bill of sale to the retailer that sold to to you...

I'm curious. Does the gauge still seem to operate normally or does it seem to read low..or high?

Kerry Borgne
Birmingham, Michigan

1963 Spyder Convertible

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Re: VairTrix CHT sensor problems?
Posted by: alphasud ()
Date: October 22, 2020 01:17PM

Yes,
Initially the gauge went to 400 degrees as part of its self check. Now it pegs and returns to 200. At normal operating temps it reads between 400-600. Seems to have shifted 200 degrees. I will need to send it back as I can’t think of anything else to check. The gauge is in mint condition from a low mileage car.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
1965 Corsa mid engine project
1973 Mercedes 280 project

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Re: VairTrix CHT sensor problems?
Posted by: Grandpacorvair ()
Date: October 22, 2020 01:42PM

Does the gauge sit at it's normal position when the key is off? If so I'd have to say the sensor is bad. If it sits 200° high when the key is off then the gauge has a problem...

Kerry Borgne
Birmingham, Michigan

1963 Spyder Convertible

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Re: VairTrix CHT sensor problems?
Posted by: azdave ()
Date: October 22, 2020 01:57PM

alphasud Wrote:
-------------------------------------------------------
> The gauge is in mint condition from a low mileage car.

You can do a simple function check if you have a few loose resistors laying around. Can you find one in the range shown between the bars on this chart and temporarily connect it between the wire at the sender and ground?

1K Ohm should just begin the move the needle.

320 Ohm would read about 400F

100Ohm should read around 500F



Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: VairTrix CHT sensor problems?
Posted by: alphasud ()
Date: October 22, 2020 04:32PM

Great thinking Dave! I was looking for info on the new sensor and didn’t even think about the original temp scale. I will check and verify the gauge accuracy.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
1965 Corsa mid engine project
1973 Mercedes 280 project

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Re: VairTrix CHT sensor problems?
Posted by: 66vairman ()
Date: October 23, 2020 09:26AM

alphasud Wrote:
-------------------------------------------------------
> Great thinking Dave! I was looking for info on the new sensor and didn’t even think about the original temp scale. I will check and verify the gauge accuracy.

That graph is for the "PASSIVE" resistance of the thermistor. Based on my experience it is NOT applicable to the gauge!! Why? Relative to today's low power electronics, the gauge amperage is considerable and caused a "self heating" effect in the thermistor sender. This results in a different resistance vs. passive resistance from heating the thermistor and then measuring it without being connected to the gauge.

Note: The EM gauge driver coils are different vs. the LM gauge coils, but they do work in a similar manner, but the resistance curves are not the same as the EM gauge tends to read a higher temperature per the sender resistance.

Anyway -- The resistance needed to get the EM gauge to 400F is about 190 ohms, but that is based on ONLY two EM gauges I checked.

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Re: VairTrix CHT sensor problems?
Posted by: Vairtrix ()
Date: October 25, 2020 05:03PM

alphasud Wrote:
-------------------------------------------------------
> I installed a VHT-100 on a EM back in the spring. I had to relocated the electronics module initially because where I placed it it was getting too hot.


It's possible that an improper installation inside the shroud may have caused a failure.

From the product installation instructions:

WARNING! The CHT-100 must be installed in the left side cylinder head only. Do not position the black epoxy inline barrel within the cooling air shroud. Overheating may occur resulting in intermittent operation or product failure!



Edited 1 time(s). Last edit at 10/25/2020 05:06PM by Vairtrix.

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Re: VairTrix CHT sensor problems?
Posted by: Spectre ()
Date: October 26, 2020 04:16AM

I will be trying one of these out when I get the heads back for my car. The old thermistor broke when removing.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: VairTrix CHT sensor problems?
Posted by: azdave ()
Date: October 26, 2020 04:50AM

66vairman Wrote:
-------------------------------------------------------

> That graph is for the "PASSIVE" resistance of the thermistor. Based on my experience it is NOT applicable to the gauge!!

I substituted a 320 Ohm resistor for the thermistor in my Corsa and the gauge read within a needle width of 400 degrees. Seems like a good way to do a quick test on his gauge to me. Might not be a perfect way to simulate the thermistor but it should still help confirm that the gauge is not reading grossly in error.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: VairTrix CHT sensor problems?
Posted by: davemotohead ()
Date: October 26, 2020 06:03AM

I thought VairTrix also made a unit that gave you head temps from both heads? if its only good for the left head how does the dual head temp set up work?







1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca

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Re: VairTrix CHT sensor problems?
Posted by: Spectre ()
Date: October 26, 2020 06:33AM

Looks like the dual unit is available from the Corvair Ranch only.

[vairtrix.com]

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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