Sender for AC temperature gauge
Discussion
I'm getting fed up with looking at a temp gauge reading about 120° when I know it's about 30° lower. I know the problem is that I have a Ford sender and an AC gauge. I've been told that I need a Vauxhall sended but can't remember which one.
It isn't an easy swap because the motor has been changed at some point so the sender hole on the manifold is sized for the Ford unit. This means that, potentially, to fix this problem I'll need to take the manifold off and have it machined to suit the correct sender.
Apart from putting a resistor in line to make it read corectly at/about the working temp does anyone have a clever fix?
It isn't an easy swap because the motor has been changed at some point so the sender hole on the manifold is sized for the Ford unit. This means that, potentially, to fix this problem I'll need to take the manifold off and have it machined to suit the correct sender.
Apart from putting a resistor in line to make it read corectly at/about the working temp does anyone have a clever fix?
Bought and installed sender... turn on ignition & gauge reads just below 40° (i.e. barely moves). Ran engine up to point where Kenlow cuts in..... temp gauge reads just over 40° .....
Putting a multimeter across the unit it has a resistance of about 70 ohms (cold), the one I took out (which over reads) is about 700 ohms cold. Nigel, any chance you could check your's? At least then I'd know if the unit is U/S or if it's the wrong one. I'm assuming TVR didn't put any clever resistance wire in the circuit, because I didn't when I re-wired it.
P.
Putting a multimeter across the unit it has a resistance of about 70 ohms (cold), the one I took out (which over reads) is about 700 ohms cold. Nigel, any chance you could check your's? At least then I'd know if the unit is U/S or if it's the wrong one. I'm assuming TVR didn't put any clever resistance wire in the circuit, because I didn't when I re-wired it.
P.
All,
With a saucepan of hot water, a thermometer and a multimeter I calibrated the sender (giving a graph of Temp vs resistance) then with a potentiometer (variable resistor) I calibrated the gauge (again temp vs resistance). As I suspected the two are miles different but, but putting a 180 ohm resistor in parallel with the sender (using R=1/((1/R1)+(1/R2)) to calculate the value needed) I got a good match (on paper) of the two curves. Have wired this in at the gauge and it seems to be giving sensible readings now.
Incidentally, when I took the gauge out to do this I noticed that the gauge is marked as 24V and the power side is fed by a length of resistor wire, is this normal?
Phil
With a saucepan of hot water, a thermometer and a multimeter I calibrated the sender (giving a graph of Temp vs resistance) then with a potentiometer (variable resistor) I calibrated the gauge (again temp vs resistance). As I suspected the two are miles different but, but putting a 180 ohm resistor in parallel with the sender (using R=1/((1/R1)+(1/R2)) to calculate the value needed) I got a good match (on paper) of the two curves. Have wired this in at the gauge and it seems to be giving sensible readings now.
Incidentally, when I took the gauge out to do this I noticed that the gauge is marked as 24V and the power side is fed by a length of resistor wire, is this normal?
Phil
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