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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #1 ·
First off I want to say how awesome it is that this forum is around, I've learned so much about my old car just from searching around here, I'm very grateful for the knowledge present.
With that said, I'm in need of more knowledge.
My car started blowing fuses, choke light comes on, voltmeter drops below 8, other guages are off. Done a lot of ground searching and finding, that has narrowed some things. Tore into the dash, and the instrument cluster does not appear damaged at all. Looked under the hood, again, and found this sensor in the block under the exhaust manifold.


Automotive tire Pliers Motor vehicle Electrical wiring Bumper
139579

Could this be the issue? I have a loose green wire that goes into the firewall, I am unsure if it is supposed to connect here, but worth a shot?
 

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That looks like a temperature sensor. That is where my after market coolant temp gauge connect. I can't tell just looking at the sensor if it is for a gauge or for an on/off idiot light. And yes after taking image I raised it's wire higher away from the header from cyl #3.
139581
 

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1984, 305, stock with edelbrock intake and carb.
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17 Posts
Discussion Starter · #3 ·
That looks like a temperature sensor. That is where my after market coolant temp gauge connect. I can't tell just looking at the sensor if it is for a gauge or for an on/off idiot light. And yes after taking image I raised it's wire higher away from the header from cyl #3.
View attachment 139581
Do you think that not being connected could cause a ground out and make my fuses blow?
Thanks for the help!
 

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I don't think the sensor itself is causing a problem.
However, if the wire from the gauge is shorting out it might cause you some problems.

If you update your Account Settings, that might help others know what year and engine and then they might be able to see what color wire is connected on theirs.
 

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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #6 ·
I don't think the sensor itself is causing a problem.
However, if the wire from the gauge is shorting out it might cause you some problems.

If you update your Account Settings, that might help others know what year and engine and then they might be able to see what color wire is connected on theirs.
Got it, thank you!
 

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1984, 305, stock with edelbrock intake and carb.
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17 Posts
Discussion Starter · #7 ·
Is it possible that that wire was moved from the neck of the thermostat (aftermarket intake) and incorrectly placed on the temp sensor between the 1 and 3? Can the connection be fixed with proper connections made? I wonder if this is what has been causing blown fuses.....🤔
 

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ElJerrad, I believe the green wire is for the temp gauge. You state the wire is loose which can easily be addressed. If the connector is the stock version, then it has a flat metal spade inside the plastic sleeve. You'll need to work on it to apply a little more tension/pressure to press it against the flat, circular head of the sensor and make good contact.

Does the 20amp fuse blow randomly or when you fidget with the green wire? What happens if this temp wire is disconnected and you've replace the 20amp fuse, do the other gauges work properly? You should not be registering any temperature readings.

Regarding why fuses blow, here are a few reasons:
  • Fraying of the wire insulation. If one of the wires is frayed and becomes exposed, it can touch the metal frame or the ground, causing a short in the circuit. The wire might move around a lot and only occasionally come into contact with a surface, causing intermittent shorts. This is still enough to blow a fuse.
  • An electrical device is malfunctioning. Internal damage to your windshield wiper motor or power locking components can cause these systems to use more current flow than normal to keep working. This will overload the circuit causing it to short.
  • A conductor is being exposed to the elements. If there is a leak somewhere in your car, fluid could be wetting the wiring harness and connection points. A wet conductor can easily cause the circuit to short.
If the fuse blows when the temp sensor is connected, the sensor needs to be tested and probably malfunctioning. One way to test the sensor is to do a continuity check with a Volt-Ohm Meter. When the engine is cold, touch one lead to the flat center terminal of the sensor and touch the other to the block. If you hear the VOM's audio sound, that indicates the temp sensor is grounded out and needs to be replaced. If you there is no audio sound, then the sensor is doing it's job and not sending a ground signal to the temp gauge.


Troubleshooting problems with our classic cars can be challenging and headaches. You just need to remember that these cars a 30+ years old and be careful trying to fix them. Many parts are brittle and don't withstand too many tugs!

Good luck!
 

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That sensor wire grounding would not cause a fuse issue. Ground would only make the temp gauge go to full hot. Most likely a wiring fault somewhere. Auxiliary items added to the IGN ports on the fuse box are also fused by the gauge fuse.
 

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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #10 ·
57, you have no idea how helpful this is!
I haven't paid attention to this green wires positioning in relation to the fuse blowing. I'll be expirementing with that asap. The fuse that blows is for the guage/choke, that's why I've been concentrating on the dash. The choke, alternator, and battery all check out with my voltmeter. All the smog is removed (I live in Missouri). I haven't found frayed wires anywhere, in the dash, under the hood, the cluster looks ok too.
Thank you!
 

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IIRC, the choke has it's own fuse. It has been a while......
 

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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #13 ·
The gauge fuse provide power to several other locations.
Here is a power distribution schematic from a 84 service manual.
Perfect, thank you! This will definitely help with more wire chasing.
Which brings me to question. I have aftermarket intake and carb with electric choke, I don't see a fuse present for a choke, is this perhaps for a manual choke, I could just be missing it too.
 

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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #17 ·
I have not, yet. Took the dash apart and didn't find anything obviously wrong with the cluster. I have a mechanic friend that has a bit more tools and know-how than me. We will be tracing more wires as soon as him and his shop is available.
 

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1984, 305, stock with edelbrock intake and carb.
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Discussion Starter · #19 ·
I believe the problem is fixed. Unscrewed the ground wire that attaches near the parking brake that comes from the fuse panel. Sanded the wire and the washer and replaced. Haven't blown a fuse since! Thank you to all of you!
 

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87 elcamino v6 4.3 t.b.i.
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I believe the problem is fixed. Unscrewed the ground wire that attaches near the parking brake that comes from the fuse panel. Sanded the wire and the washer and replaced. Haven't blown a fuse since! Thank you to all of you!
That's odd....hmm.... Well good for you oh, and I will keep that ground wire in mind if I ever have electrical issue. Safe driving
 
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