is there a fusable link

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trudysduster

trudysduster

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Is there a fusable link in the wire going from the temp sender to the instrument cluster on a 1976 Duster. I now have a 440 engine in it. I thought I would try this and it didn't work. I wanted to check the accuracy of the factory gauge in the instrument cluster so I bought a separate temp gauge and hooked it to the sending unit along with the factory one to compare them and I guess something must have back fed to the factory gauge because it wouldn't work. I bought another factory gauge from a member on here and changed out the gauge in the cluster and that one isn't working. So I either got a bad gauge from him or I must have blowed something in the wire from the sending unit to the cluster. Doe anybody have any input on this.
 
Think of the sender like a resistor to ground, seriously doubt you blew it out unless did you put 12 VDC to it? Pretty easy to check with a ohm meter take it off the sender and check the wire from the gauge plug to the other end it should be open not hooked up and 0 id you ground the sender end at the engine. Turn the KEY OFF when you do it hope this helps.
 
halifaxhops said:
Think of the sender like a resistor to ground, seriously doubt you blew it out unless did you put 12 VDC to it? Pretty easy to check with a ohm meter take it off the sender and check the wire from the gauge plug to the other end it should be open not hooked up and 0 id you ground the sender end at the engine. Turn the KEY OFF when you do it hope this helps.
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what I did was take the new temp gauge and lay it on the fender. I ran a hot wire from the new gauge to pos. side of battery like the diagram showed. I ran a neg. wire from gauge to gnd. and it had a wire from gauge to sending unit. as soon as I hooked this up it pegged the needle on the new temp gauge. I unhooked the wire from the sending unit and the needle returned back to the low side. Touched it again to the sending unit and it pegged again. So I unhooked the wire going to the cluster from the sending unit and hooked up the wire from the new gauge and it was fine. so I assumed it was back feeding or something. I went ahead and ran the car with the new gauge to check how hot it was running. when I was done, I unhooked the new gauge and plugged in the factory wire nd that is when I noticed the gauge in the cluster wasn't working anymore. I got another factory gauge from a member and installed it in the cluster and hooked it up and it doesn't work either. so I don't know what the hell I did.
 
You have which sending unit in now the original or the aftermarket? Usually they are a different range. Sounds like you did not fry anything to me. Just check the oem sending unit wire for continuity and that it is not grounded somewhere, also the bulk head connection can be dirty and it just got to the point of not conducting, yes a long shot but easy to check, The other gauges still work?
 
from memory I think the range on the sending unit is 10-73 ohms.
 
There is a instrument cluster voltage regulator (on the back of the cluster), that applies a pulsating voltage to the gauges. This voltage averages approx 5 volts. The senders (fuel, temp, and on some models oil) are variable resistors that make the ground side of the circuit. If you apply full 12 volts to the gauges for more then a few seconds, you can burn out the gauge. Take a 12 volt test light an connect it to the wire that has been removed from the temp sensor. Then turn on the key, and see if the test light blinks, and the gauge comes off zero. If the light blinks and the gauge moves, the sender is probably bad. If the light does not blink, you might have a bad CVR (constant voltage regulator) or a bad gauge. Also possible to have a bad connection, at/on the cluster.
 
Totally agree, if the IVR is burned out all three gauges are bad, think it is just the temp for him.
 
halifaxhops said:
Totally agree, if the IVR is burned out all three gauges are bad, think it is just the temp for him.
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fuel gauge is working. Sender has to be working because when I hook up the new temp gauge it works fine while hooked to the temp sending unit. How do you test the temp gauge out of the cluster.
 
trudysduster said:
fuel gauge is working. Sender has to be working because when I hook up the new temp gauge it works fine while hooked to the temp sending unit. How do you test the temp gauge out of the cluster.
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Good at electronics or have a basic understanding?
 
halifaxhops said:
Totally agree, if the IVR is burned out all three gauges are bad, think it is just the temp for him.
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I am going to change out this temp sending unit. I took the wire that plugs onto the sending unit and grounded it and the needle on the gauge in the cluster went to the hot side so maybe the sending unit is bad.
trudysduster said:
I do have electronic understanding.
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I unplugged the wire from the temp sending unit on the engine and hooked a wire from it to gnd and the needle on the gauge in the cluster went all the way over to the hot side so it may be the temp sending unit after all. I am going to change it out and check it again.
 
10 ohm is full, 23 is mid range and 74 is low if you need the specs.
 
halifaxhops said:
you just did the test it is the sending unit for sure.
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I dont know if it is or not. I changed the sending unit out with a new one. Hooked the wire up. Started the car and let it run a little and the temp gauge didn't move at all. I pulled the wire off again and hooked an alligator clip on it and grounded it and the needle went all the way to the hot side. so what the hell could that be.
 
Bill it would NOT BE UNHEARD OF that a brand new sender is bad/ defective, especially with the Chineseoizationophonishized state of replacement parts. Also, GO EASY on the wrench. You could have damaged it with over tightening.
 
67Dart273 said:
Bill it would NOT BE UNHEARD OF that a brand new sender is bad/ defective, especially with the Chineseoizationophonishized state of replacement parts. Also, GO EASY on the wrench. You could have damaged it with over tightening.
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Well, I am going to try another sending unit tomorrow and see. May have to tap the threads and try again.
 
I have a few oem used ones if you want to try one. Weird for sure.
 
ohm out the sending unit to see if it is open should be at least 73 ohms cold.
 
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