did i check this correctly
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
did i check this correctly
I keep reading about temp senders being incorrect so i wanted to check mine.
i found a chart that gave ohm readings for given temps.
the chart said 90ohms for 200 degrees.
i hooked up my ohm meter to my gauge and dropped it into hot water. at 200 degrees the gauge read 50 ohms.
if i checked the sensor correctly it will explain why it reads high on my gauge.
i found a chart that gave ohm readings for given temps.
the chart said 90ohms for 200 degrees.
i hooked up my ohm meter to my gauge and dropped it into hot water. at 200 degrees the gauge read 50 ohms.
if i checked the sensor correctly it will explain why it reads high on my gauge.
Last edited by baxsom; Feb 16, 2009 at 10:51 AM.
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
That's probably not too far off for that sender. It is 90 ohms at full scale; 200 deg. is a little above half-way on the gauge and so is 50 ohms (on a 90 ohm sender). I would suspect that the sender is good.
Check the gauge by removing the wire from the sending unit (with ignition in ACC position); with wire "open" gauge should move to one side of the scale. Then touch that wire end to engine block metal [or other chassis ground point] and needle should swing to the other side of the gauge scale. If that works, the gauge is fine. If not, either the gauge is bad or the wiring between gauge and sender is bad.
Check the gauge by removing the wire from the sending unit (with ignition in ACC position); with wire "open" gauge should move to one side of the scale. Then touch that wire end to engine block metal [or other chassis ground point] and needle should swing to the other side of the gauge scale. If that works, the gauge is fine. If not, either the gauge is bad or the wiring between gauge and sender is bad.
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
its not that its a bad sender. it is the sender is not the correct one for the car.
that sender reads 250 on the gauge when the aftermarket gauge and sender reads 210.
so further reading on this site turned up that parts houses temp senders were not reading correctly because the resistance is incorrect for the car. the correct sender for a 72 vette will be at 90ohms when the coolant is 200 degrees. the one i was sold is almost half of that at the same temperature. therefore the sender is the wrong one. the lower the resistance the higher the gauge goes so if the gauge is calibrated to read 200 degrees with 90 ohms of resistance then 50 ohms does explain the high reading.
looks like i have to go lectric limited as well to get a correct one. i wish i would have seen this before i pulled out the mechanical fan and did all of the work of an electric one thinking i had an overheating problem when it was the sensor instead.
oh well at least i have room for a spreader bar now.
that sender reads 250 on the gauge when the aftermarket gauge and sender reads 210.
so further reading on this site turned up that parts houses temp senders were not reading correctly because the resistance is incorrect for the car. the correct sender for a 72 vette will be at 90ohms when the coolant is 200 degrees. the one i was sold is almost half of that at the same temperature. therefore the sender is the wrong one. the lower the resistance the higher the gauge goes so if the gauge is calibrated to read 200 degrees with 90 ohms of resistance then 50 ohms does explain the high reading.
looks like i have to go lectric limited as well to get a correct one. i wish i would have seen this before i pulled out the mechanical fan and did all of the work of an electric one thinking i had an overheating problem when it was the sensor instead.
oh well at least i have room for a spreader bar now.
Last edited by baxsom; Feb 16, 2009 at 04:30 PM.
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
Update...
the local corvette restorer had a unit he guaranteed worked. I got it home and did the same dunk in hot water test. when the thermometer hit 200 degrees the resistance was 90.5 ohms. right where the chart says it is supposed to be.
cool
the local corvette restorer had a unit he guaranteed worked. I got it home and did the same dunk in hot water test. when the thermometer hit 200 degrees the resistance was 90.5 ohms. right where the chart says it is supposed to be.
cool
