69 Big Block Temperature Sensor
Thread Starter
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
69 Big Block Temperature Sensor
I'd like to determine whether the sensor or the gauge is at fault. Mine seems to read low. What would be very helpful is a table of sensor resistance vs temperature. I could then use a multimeter to measure the resistance at various water temperatures.
Has anyone seen such data on the sensor? Has anyone got a "good" sensor from a 69 BB they might be able to measure?
I guess that there may be a few folks on the forum might like to see this data. There have been many temp gauge questions and problems.
Many Thanks
Joe
69 427L36 M21 3.08 White Coupe
Has anyone seen such data on the sensor? Has anyone got a "good" sensor from a 69 BB they might be able to measure?
I guess that there may be a few folks on the forum might like to see this data. There have been many temp gauge questions and problems.
Many Thanks
Joe
69 427L36 M21 3.08 White Coupe
Instructor
Joined: Jun 2002
Posts: 117
Likes: 0
From: epping nh
Re: 69 Big Block Temperature Sensor (jyounane)
I believe if you ground it it should deflect completly one way. Not 100% sure though.You can find this from some tech manual the gm guy pulled out at a Power Fest show.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: 69 Big Block Temperature Sensor (jyounane)
My new temp sensor read 40 degrees hotter than actual. I was told to expect this when I bought the replacement from the Chevy parts guy. I used a 15 ohm resistor from Radio Shack to bring within 5 degrees of actual. I bought many resistors to end up with one that would be the closest. Hope this helps.
Chuck
Chuck
Thread Starter
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
Re: 69 Big Block Temperature Sensor (Chuck Harmon)
Thanks For the replies.
I think we need two points to check the sensor, say around 75deg and 180deg. If I had the resitance readings at those two temperatures, I could check my sensor with some hot water, a thermometer and the multimeter.
Your info, Chuck, suggests that 15 ohms change corresponds to about a 40deg temp difference, but may not help me check my sensor directly.
Best regards,
Joe
69 427L36 M21 3.08 White Coupe
I think we need two points to check the sensor, say around 75deg and 180deg. If I had the resitance readings at those two temperatures, I could check my sensor with some hot water, a thermometer and the multimeter.
Your info, Chuck, suggests that 15 ohms change corresponds to about a 40deg temp difference, but may not help me check my sensor directly.
Best regards,
Joe
69 427L36 M21 3.08 White Coupe
Burning Brakes
Joined: Jul 2001
Posts: 853
Likes: 0
From: Foxfield, Co
Re: 69 Big Block Temperature Sensor (jyounane)
A new GM replacement sensor I bought [it has the number 45 stamped on the bottom of it] measured like this:
100* = 411 ohms
110* = 355
120* = 297
130* = 259
140* = 227
150* = 198
160* = 172
170* = 151
180* = 129
190* = 112
200* = 100
205* = 95 ohms
I found using this sensor with a 10 ohm resistor in series with it keeps my gauge within about 5 degrees of the mechanical gauge I installed in the passenger side head. Surprisingly it is pretty accurate across the whole temp range. Hope this helps. :D
100* = 411 ohms
110* = 355
120* = 297
130* = 259
140* = 227
150* = 198
160* = 172
170* = 151
180* = 129
190* = 112
200* = 100
205* = 95 ohms
I found using this sensor with a 10 ohm resistor in series with it keeps my gauge within about 5 degrees of the mechanical gauge I installed in the passenger side head. Surprisingly it is pretty accurate across the whole temp range. Hope this helps. :D
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: 69 Big Block Temperature Sensor (jyounane)
If you have access to an ohm meter, you may want to check the connection to your gauge. You may have an unintended point of resitance in your line. To calibrate my gauge, I bought a cheap mechanical temp gauge that I attached in the plug on the other head. (I checked this cheap guage with a pan of boiling water.) Don't assume that your gauge is reading too low. On the road my Big Block is only 180 degrees with a 180 thermostat.
But if it is truly reading too low, most likely, they gave you the wrong part and you need to try another. What's nuts is even if they give you the right part it will read too hot and you will most likely have to do what I did.
Chuck
p.s. The 15 ohm only dropped it by 35 degrees. 17 probably would have nailed it, but the next step was 20+ ohms.
But if it is truly reading too low, most likely, they gave you the wrong part and you need to try another. What's nuts is even if they give you the right part it will read too hot and you will most likely have to do what I did.
Chuck
p.s. The 15 ohm only dropped it by 35 degrees. 17 probably would have nailed it, but the next step was 20+ ohms.
Thread Starter
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
Re: 69 Big Block Temperature Sensor (Chuck Harmon)
Greg454, Chuck,
Thanks for your help. My car has original sensor and Gauge. Just seems to read very low. I think wiring is ok, I suspect gauge.
I like the idea of using a mechanical gauge in the other head, might give that a go. Thanks Greg454 for your readings. I was surprised to see how non-linear the readings are. However, that gives me a real set of sensor readings to compare mine to. I'll do that on the weekend and let you know.
Best regards,
Joe
69 427L36 M21 3.08 White Coupe
Thanks for your help. My car has original sensor and Gauge. Just seems to read very low. I think wiring is ok, I suspect gauge.
I like the idea of using a mechanical gauge in the other head, might give that a go. Thanks Greg454 for your readings. I was surprised to see how non-linear the readings are. However, that gives me a real set of sensor readings to compare mine to. I'll do that on the weekend and let you know.
Best regards,
Joe
69 427L36 M21 3.08 White Coupe
Burning Brakes
Joined: Jul 2001
Posts: 853
Likes: 0
From: Foxfield, Co
Re: 69 Big Block Temperature Sensor (jyounane)
Joe, measuring the gauge in water is not an exact science. the readings on the way up aren't exactly the same as the way down. And having the thing in boiling water lets the sensor bounce around quite a bit. So don't take the readings as gospel. The best way I found to be sure your gauge is accurate is to compare it to a mechanical gauge in the car.
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