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Danny604
Samba Member
Joined: October 09, 2019
Posts: 89
Location: Port Coquitlam BC Canada
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 Posted: Fri Jun 04, 2021 10:18 pm Post subject: Cylinder head temp idiot light |
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Reading the Bill Fisher, How to hotrod your VW book. They mention using a Corvair head temp sensor/switch that turns on an idiot light when they are getting too hot. I searched for the sensor online but only came up with NOS ebay parts and out of stock items. Is anyone doing this anymore? modern solution for an idiot light?
Thanks |
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15303
Location: Deep in the 405
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| Posted: Fri Jun 04, 2021 10:21 pm Post subject: Re: Cylinder head temp idiot light |
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Those little sensors you put on the head and wired to the idiot light have long ago been discontinued.
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Wreck
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Joined: July 19, 2014
Posts: 1218
Location: Brisbane
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| Posted: Fri Jun 04, 2021 11:13 pm Post subject: Re: Cylinder head temp idiot light |
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Not a cheap option but a good one . MGL TC-1 gauge has an adjustable alarm for over temp . It can be configured for different thermocouples from memory .
photo for reference , I've set mine at 180C (well under max allowable)
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dubman67
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Joined: April 10, 2003
Posts: 273
Location: Big Sky Country
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Danny604
Samba Member
Joined: October 09, 2019
Posts: 89
Location: Port Coquitlam BC Canada
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| Posted: Sat Jun 05, 2021 7:42 am Post subject: Re: Cylinder head temp idiot light |
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| I was planning to have a boss welded to the head and thread it into that. Thanks for the link. I agree with not wanting to have a gauge, I feel the same way. |
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FreeBug
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Joined: March 12, 2012
Posts: 4278
Location: deepest, darkest Switzerland
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| Posted: Sat Jun 05, 2021 12:50 pm Post subject: Re: Cylinder head temp idiot light |
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| I still have one, somewhere, I used it on my bus engine, never see ed to work like it should have, never really warned me of anything the other gauges didn't. Even a GB227 would be better, in my opinion. |
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VW_Jimbo 
Samba Member
Joined: May 22, 2016
Posts: 9960
Location: Huntington Beach, CA
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| Posted: Sat Jun 05, 2021 2:03 pm Post subject: Re: Cylinder head temp idiot light |
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I run a dipstick sensor and a head temp gauge.
Dipstick sensor is a brilliant idea. You can check it out here.
https://www.busdepot.com/gb228
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raygreenwood
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Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Sat Jun 05, 2021 10:32 pm Post subject: Re: Cylinder head temp idiot light |
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It should not be too hard to make "something" that works like this reliably.
A few ways to do it. Something like these just for an example of what to look for.
https://www.wika.us/tfs135_en_co.WIKA
Hundreds of sizes, configurations and temperatures. Its just a bi metallic switch tjat is normally open. When it hits temp it closes and turns on your warning light.
Ray |
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mondshine
Samba Member
Joined: October 27, 2006
Posts: 2769
Location: The World's Motor Capital
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| Posted: Sun Jun 06, 2021 4:58 am Post subject: Re: Cylinder head temp idiot light |
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Westach publishes the MV output for their Type J thermocouples (with the cold junction at 75º F).
A creative electronics wiz could assemble a circuit to trigger a relay for a dashboard warning light at a given MV output from the thermocouple. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Sun Jun 06, 2021 7:45 am Post subject: Re: Cylinder head temp idiot light |
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| mondshine wrote: |
Westach publishes the MV output for their Type J thermocouples (with the cold junction at 75º F).
A creative electronics wiz could assemble a circuit to trigger a relay for a dashboard warning light at a given MV output from the thermocouple. |
Yes....but....without cold leg temperature compensation.....the temperature that TC causes the alarm or warning light to go off at..... will vary widely.
Just stating the above fact for the record ......because you are right.... a thermocouple is a good and cheap idea.
The reason I did not suggest using a thermocouple.....is because I figured those looking at this thread wanted one that was dirt simple.....like single wire simple?
If one has enough electronics know how to design a logic circuit to trigger a relay or open a circuit for an LED or light bulb.....when the TC is sending the exact current level that corresponds to whatever temperature you consider too high.......you can easily build the small circuit I found the plans for on line last year for a compensation circuit for almost any TC so any gauge can be temperature compensated.
If you can solder.....its about $20 in parts or I think the guy is selling kits.
But......if you can do all of that.....you are basically building a gauge.
Ray |
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mondshine
Samba Member
Joined: October 27, 2006
Posts: 2769
Location: The World's Motor Capital
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| Posted: Sun Jun 06, 2021 7:54 am Post subject: Re: Cylinder head temp idiot light |
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| raygreenwood wrote: |
But......if you can do all of that.....you are basically building a gauge.
Ray |
Yep; that's why I use a gauge. 
I assumed that the OP did not want to clutter (or hack) his IP with non-stock
instruments. |
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