Temperature sender adjustable resistor - variable
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Texas
Temperature sender adjustable resistor - variable
http://www.parts123.com/parts123/yb....Z5Z5Z50000050x
Has anyone one ever use one of these variable resistors to correct a inaccurate C1 temp gauge?
My gauges are all freshly reconditioned...but my temp gauge is reading high.
Thanks...Stan
Has anyone one ever use one of these variable resistors to correct a inaccurate C1 temp gauge?
My gauges are all freshly reconditioned...but my temp gauge is reading high.
Thanks...Stan
Safety Car
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From: Lexington,NC,USA
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I used a potentiometer to adjust the gauge on my wife's 62. The resistance of the sender is not linear so the best you can do with a variable resistor is make it accurate at only one temperature - I chose 180°.
Charles
Charles
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Cbernhardt is right.. It'll work at one point.. but won't be right anywhere else on the gauge. That can cause a problem if you overheat.
IMHO,
Willcox
IMHO,
Willcox
Last edited by Willcox Corvette; Jan 23, 2016 at 08:52 AM.
Le Mans Master
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From: Arlington TX
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Mine read about 200 deg. after trying three sensors. IR gauge read about 175, so added a 10 ohm resister. Read about 190, so removed the 10 & added a 15. Stays right on 180. I assume that the gauge will rise if I truly have an overheating condition sometime.
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Jim
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From: Las Vegas - Just stop perpetuating myths please.
Now adding resistance to your sender/sensor wire will "shift" the entire output plot. Hard to tell if that is what your gauge problem is. But Stan how can we be convinced your gauge is reading "high"? U really need to calibrate your sending unit to your dash gauge. This is easily done with extension wire used to put the sender/sensor into a hot plate pot of water and use a thermometer (mouth thermometer or whatever u have) to trend the temp and see if it matches your gauge.
If u have a mismatch in temp readings then u may need a replacement gauge or at least have yours re-calibrated. Corvette Instruments is still in business AFAIK. U could try that variable resistor and see if can correct the problem u have.
Most owners are having problems when changing to alum heads and the old 3/4" NPT sensor now wont fit in the 5/8" hole in the cyl head while the 5/8" sensors have a different resistance curve. The best fix i know of is just take your old (or replacement) 3/4" sensor to a shop that can turn it down to 5/8" NPT.
Hope this can help as im not really sure where your temp gauge problem is.
If u have a mismatch in temp readings then u may need a replacement gauge or at least have yours re-calibrated. Corvette Instruments is still in business AFAIK. U could try that variable resistor and see if can correct the problem u have.
Most owners are having problems when changing to alum heads and the old 3/4" NPT sensor now wont fit in the 5/8" hole in the cyl head while the 5/8" sensors have a different resistance curve. The best fix i know of is just take your old (or replacement) 3/4" sensor to a shop that can turn it down to 5/8" NPT.
Hope this can help as im not really sure where your temp gauge problem is.
Last edited by cardo0; Jan 23, 2016 at 11:30 AM.
Le Mans Master
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Yes, it will rise but by only a small amount. IOW, the engine can be really, really hot and the gauge will tell you that it's only slightly above 180. You will be lulled into a false sense of security. That's the true risk of using a fixed resistor to "calibrate" a temperature gauge to the sender.
Jim
Jim
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Thread Starter
Melting Slicks
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From: Texas
I'm pretty sure either the sender or gauge is off...but to clarify.
My engine is a new just out of the crate ZZ4...and all my instruments are unused till now and were reconditioned/upgraded by a company in Florida a couple of years ago...the name of which eludes me, but well known and one MIke Coletta uses. I've forgotten the origin of the temp sender...as I have been gathering parts a long time....but it is a 3/4 " NPT thread.
The engine doesn't seem warm but the gauge fluctuates from 180-200. IR thermometer readings are under 180 considerably...( I also bought a new IR thermometer to double check the one I already had). The thermostat is a Mr.Gasket 180 degree (Robert Shaw type)
I have a new BeCool radiator like Corvette Correction uses...and a have a full time high flow Spal fan like Mike Coletta and others use.
For the initial start up...the timing was at 10 degrees with no vac advance...and the new SMI Quadrajet Carburetor adjusted perfectly with the lean drop beginning at 1 -1/4 turns out on both jets.
Sooo...the variable resistors are inaccurate except in one spot?? That's next to worthless isn't it...???
Thanks...Stan
My engine is a new just out of the crate ZZ4...and all my instruments are unused till now and were reconditioned/upgraded by a company in Florida a couple of years ago...the name of which eludes me, but well known and one MIke Coletta uses. I've forgotten the origin of the temp sender...as I have been gathering parts a long time....but it is a 3/4 " NPT thread.
The engine doesn't seem warm but the gauge fluctuates from 180-200. IR thermometer readings are under 180 considerably...( I also bought a new IR thermometer to double check the one I already had). The thermostat is a Mr.Gasket 180 degree (Robert Shaw type)
I have a new BeCool radiator like Corvette Correction uses...and a have a full time high flow Spal fan like Mike Coletta and others use.
For the initial start up...the timing was at 10 degrees with no vac advance...and the new SMI Quadrajet Carburetor adjusted perfectly with the lean drop beginning at 1 -1/4 turns out on both jets.
Sooo...the variable resistors are inaccurate except in one spot?? That's next to worthless isn't it...???
Thanks...Stan
Last edited by Stan's Customs; Jan 24, 2016 at 07:15 AM.
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Thread Starter
Melting Slicks
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From: Texas
Thanks...Stan
PS..off topic but do you know how much vacuum your ZZ4 pulls at idle (about).
Thanks...Stan
Last edited by Stan's Customs; Jan 24, 2016 at 10:03 AM.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
All Chevy sending units and dash gauges are non-linear. On 1965 and new gauges I made a adjustable resistor which will allow the gauges to be adjusted. On the cars older than 1965 I don't have anything that will work because they didn't use the external resistor.
Melting Slicks
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From: Imperial Missouri
I do actually have a vacuum boost gauge hooked up all the time and it reads around 17-18. I'm using GMs HEI that came with the engine without any vacuum hookup. I did put hardened a gear on my old HEI with tach drive but haven't ever used it. I'm running a QF 650 square bore with mechanical secondaries.
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Texas
Yes. I did see it hit 180 one time when waiting in a long line to get into a car show but it still ran fine when a lot of cars quit on them. I did try to find a different sending unit but because of the size of the hole this is the only one for my intake.
I do actually have a vacuum boost gauge hooked up all the time and it reads around 17-18. I'm using GMs HEI that came with the engine without any vacuum hookup. I did put hardened a gear on my old HEI with tach drive but haven't ever used it. I'm running a QF 650 square bore with mechanical secondaries.
I do actually have a vacuum boost gauge hooked up all the time and it reads around 17-18. I'm using GMs HEI that came with the engine without any vacuum hookup. I did put hardened a gear on my old HEI with tach drive but haven't ever used it. I'm running a QF 650 square bore with mechanical secondaries.
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Ya know each sensor manufacturer has a thermistor with a little different resistance curve. U can buy the assortment of sensors to try but u still need to know what the actual temp is and sorry but the IR gun aint close enough. U really need to dunk the sensor in a bath and hook up with extension wire to see what the gauge really reads.
Something else is your system voltage will affect the gauge reading so if that has changed enough the gauge will be off.
Something else is your system voltage will affect the gauge reading so if that has changed enough the gauge will be off.
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 3,022
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From: Texas
Ya know each sensor manufacturer has a thermistor with a little different resistance curve. U can buy the assortment of sensors to try but u still need to know what the actual temp is and sorry but the IR gun aint close enough. U really need to dunk the sensor in a bath and hook up with extension wire to see what the gauge really reads.
Something else is your system voltage will affect the gauge reading so if that has changed enough the gauge will be off.
Something else is your system voltage will affect the gauge reading so if that has changed enough the gauge will be off.
Good idea on the bath...but the pot of hot water it's in would have to be grounded as well.
Regarding voltage and grounding..I suppose a poor engine ground could be a factor on the temp gauge accuracy on one of these cars also...
Thanks...Stan
Last edited by Stan's Customs; Jan 24, 2016 at 06:29 PM.
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What Cardo0 says is exactly right. The resistor needs to be variable, and usually of the thermistor type, which drops resistance as it gets hotter. The right way to do it is to get the exact sending unit with the right curve. Had this issue with my old GTO's, and found that the generic temp sending units were not calibrated correctly. Installed Lectric Limited senders, and now have accurate temp gauges.
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 3,022
Likes: 95
From: Texas
What Cardo0 says is exactly right. The resistor needs to be variable, and usually of the thermistor type, which drops resistance as it gets hotter. The right way to do it is to get the exact sending unit with the right curve. Had this issue with my old GTO's, and found that the generic temp sending units were not calibrated correctly. Installed Lectric Limited senders, and now have accurate temp gauges.
Stan..
Last edited by Stan's Customs; Jan 24, 2016 at 07:09 PM.