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I am brand new here, just learning about my recently purchased ‘66 vette (from father). I recently changed the fuel sending unit out as the fuel gauge has never worked since my father bought the car in ‘81. I got everything reconnected and it worked, I just needed a new ground connection to the sending unit after all. Then I started blowing fuses about 5 minutes into starting the car. After learning the fuel sending unit and water temp gauges are on the same circuit (in this forum so thank you!) I changed the fuse and was good to go!
However I blew a fuse about 5 minutes after starting the car and watching the fuel gauge work for the first time since my father bought the car. To make it worse I then decided to change the water temp wire as the insulation was mostly frayed off and seemed an easy task. I butt spliced the wire and re insulated it.
I think there may be a short in the wire harness to the fuel sending unit, so I disconnected that (I grew up learning to just check fuel level before driving it) and assumed I would at least have a water temp gauge until I further investigated the wiring.
However, now I am still blowing fuses with the fuel sending unit ground disconnected (that was how it has been for the past 43 years).
The only thing I can think of that has changed is the butt splice of the water temp wire I did to re-insulate that. Could that really be the issue? I’m not an electrician but it seems like a silly reason to blow a fuse. If so then I would need to replace that wire all the way back to the gauge correct?
sorry for the long post, I just wanted to convey everything that I did. I am enjoying learning about the mostly simplistic way the car works but this has me stumped. Next generation kid where I didn’t grow up with these cars….any help is greatly appreciated!
I doubt the wire splice on the temp sender wire caused the issue. Since it’s not an immediate fuse blow that would seem to lessen the possibility of a pinched wire running back to the fuel gage. Outside of that I’m no help. You will probably just have to use the wiring diagram and trace out every circuit-related wire and inspect it and all connections.
Welcome to the obsession.
Have to tried to unhook the body connector and see if the problem with the heat gauge is eliminated? That will tell you if the problem is with the wire to the tank or under the dash. oe may also tell you if the heat gauge wire is the problem.
I extend the leads on my multimeter and check the resistance of the wire from both ends (at the connector and at the fuel gauge) to help locate a short.
Ron
Adam - Welcome to the Corvette Forum. I believe you have to reach a certain number of posts before you can access the PM system but you'll hit it soon, I'm sure.
Saw a pic of your Nassau Blue 66 and it looks great. If you have some time in late September, maybe come on up to Prescott for the local Corvette Show.
They typically get 300 or so Corvettes, with most being late models but the last couple years, there were around 45-50 chrome bumper Vettes in attendance.
Here's a YouTube Video of the 2022 Prescott Vette Sette Show. My Nassau Blue 66 Roadster won Best of Class that year and yes, I do believe in Bribery :-O.
Thank you! Yes I did isolate the fuel and temp units, and the issue is at the temp wire or gauge. I need to take the dash out and see if I can get some readings on the wire. Not looking forward to it but that’s part of the fun. Trying to get this issue resolved before it gets really hot and I store the car for the summer. It’s weird here, driving season is backwards from where I grew up!
I will see what I can do, but I don’t think mine will compete with yours, is that a BB I see? Looks great! I’ve got lots of projects to get her back in pristine condition. She looks great from a distance and runs well (It will always be a driver car), the paint job (roughly ‘95?) was worth 3 times what my dad paid, still looks amazing almost 30 years later.
Adam - My 66 was bought in '21 and it went through a body-off back around '91, paint and all. It does look great, better than any other midyear I've bought. Most times, I have to trailer them home followed by a ton of work afterwards but
the 66 BB Roadster was cosmetically in great shape, just needing the usual for cars that sit around a lot, like heater core replacement, carb rebuild, starter shimming, gauge issues, etc. Happens to most of them when they just sit.
When I got it home, I remember turning on the heater blower and hearing all three speeds for the fan but oddly, no air coming out...anywhere. Seems all that sitting, back in New Jersey where it came from, let the small rodents
build a 'mouse house' in the plenum, using the firewall insulation. Check out the pic of the old insulation I removed from the plenum.
Mine started out as a real 66 L72 but by the early 80's the original engine and trans were MIA. There's a good M20 wide ratio Muncie in there now and a 68-vintage 396 that runs perfectly and with the bolt ons like intake, carb,
exhaust manifolds, etc, to the naked eye, it looks like the original 427. The only drawback is the 396 is a sedate engine with a very mild cam. I've already picked up a 4-bolt 66 L72 block and 67 L-88 GM aluminum heads and intend
on building my own high horse, but NOM, L72.
Your comment about these cars being drivers is right on the money. It's nice to admire them sitting in the garage but not nearly as much fun as when we take them out and drive them.
One other comment to make...did you keep the 'old' fuel tank sending unit? The new repro's (GM stopped selling originals years ago) are a hit and miss situation and if you still have the original unit, it can be rebult.
Good luck with your 66 and keep us posted on your progress.
Mike T - Prescott AZ
You don't need to take the dash out to check the temp gauge and wire. There are only two wires on the gauge. One connects to the switched 12v via the gauges fuse, and the other runs directly through the bulkhead connector to the sender. If there is a short in the wire going to the sender, the gauge will read full scale pegged with a good fuse in. Is yours doing that? The gauge itself or perhaps the 12v wire on the gauge could be shorted to the case on the gauge, but the fuse would blow in seconds, not 5 minutes. Your parking brake warning lamp and the back up lamps are connected via that same fuse. Make sure the fuse isn't blowing when you go into reverse due to a short at the switch on the transmission.
Adam - My 66 was bought in '21 and it went through a body-off back around '91, paint and all. It does look great, better than any other midyear I've bought. Most times, I have to trailer them home followed by a ton of work afterwards but
the 66 BB Roadster was cosmetically in great shape, just needing the usual for cars that sit around a lot, like heater core replacement, carb rebuild, starter shimming, gauge issues, etc. Happens to most of them when they just sit.
When I got it home, I remember turning on the heater blower and hearing all three speeds for the fan but oddly, no air coming out...anywhere. Seems all that sitting, back in New Jersey where it came from, let the small rodents
build a 'mouse house' in the plenum, using the firewall insulation. Check out the pic of the old insulation I removed from the plenum.
Mine started out as a real 66 L72 but by the early 80's the original engine and trans were MIA. There's a good M20 wide ratio Muncie in there now and a 68-vintage 396 that runs perfectly and with the bolt ons like intake, carb,
exhaust manifolds, etc, to the naked eye, it looks like the original 427. The only drawback is the 396 is a sedate engine with a very mild cam. I've already picked up a 4-bolt 66 L72 block and 67 L-88 GM aluminum heads and intend
on building my own high horse, but NOM, L72.
Your comment about these cars being drivers is right on the money. It's nice to admire them sitting in the garage but not nearly as much fun as when we take them out and drive them.
One other comment to make...did you keep the 'old' fuel tank sending unit? The new repro's (GM stopped selling originals years ago) are a hit and miss situation and if you still have the original unit, it can be rebult.
Good luck with your 66 and keep us posted on your progress.
Mike T - Prescott AZ
Hi Mike,
Funny you ask, I have been keeping most of the items I replace but I did not keep the original sending unit, what a dummy. I forgot to mention during my whole investigation in this I did replace the temp sending unit as well, and that may have been the culprit to my fuses. I have ran the car in the garage a couple times with no blown fuses, going to take it out for a drive this afternoon and see how it works!
I do see what you mean with the fuel sending units, I am definitely not getting an accurate reading on the fuel level, but I am used to checking the gas the ol fashioned way before I take it out anyways, so not a huge deal.
You don't need to take the dash out to check the temp gauge and wire. There are only two wires on the gauge. One connects to the switched 12v via the gauges fuse, and the other runs directly through the bulkhead connector to the sender. If there is a short in the wire going to the sender, the gauge will read full scale pegged with a good fuse in. Is yours doing that? The gauge itself or perhaps the 12v wire on the gauge could be shorted to the case on the gauge, but the fuse would blow in seconds, not 5 minutes. Your parking brake warning lamp and the back up lamps are connected via that same fuse. Make sure the fuse isn't blowing when you go into reverse due to a short at the switch on the transmission.
Unfortunately no it doesnt read full scale, it starts on the left and when the fuse blows it stick right around 150 degrees. I honestly forgot I replaced the temp sending unit during all this, but I have the original and put that back in. Taking it out today to see if that maybe was the culprit. Thanks again for the info!
05-04-2024, 05:25 PM
‘66 wiring issue
