stmyrick

My '67 gas gauge keeps blowing fuses; I've slowly progressed in changing to higher amp fuses (now at 4), but still blowing them. No other ground issues. I'm afraid to install higher amp fuse for fear of a fire. Car on blocks for winter and could string another wire; or could put in new sending unit (but that doesn't seem sensible to me?). Next step?
Thanks.

65GGvert

Well, I'm not sure exactly what you have going on, but the fuel gauge (and other gauges and b/u lights) are on the same fuse, a 10 amp fuse. It's the top one in the fuse box. The 4a "inst amp" fuse is for the dash lights.

PS If that's the fuse you're blowing ("gauges"), it's probably blowing when you use reverse if you have a 4a fuse in that spot.

Frankie the Fink

Unlike other vintage Corvettes, the midyears use a "powered" sending unit that talks to the dash gauge through a voltage divider circuit (nobody knows why these cars have this extra complication)... I would bet that "power" wire to the sending unit is pinched or shorting out somewhere, somehow...

DansYellow66

Delete - I keep forgetting Corvette isn't like my GTX fuel gage wiring. Here is a wiring schematic if it helps.

65GGvert

AFTER you've verified the fuse as I mentioned earlier, remember that the temp gauge, (and I believe the parking brake warning light switch) and b/u lights are also on that fuse. You may not have a fuel gauge problem. If you suspect it's in the sender, disconnect the pink wire at the sender and see how the fuse does. If you suspect a pinched or shorted wire, disconnect the rear body connector just to the left of the steering wheel under the dash. The b/u lamps go through that connector too, but not the b/u switch power. The b/u switch can be shorted and blow that fuse even if the lamps are good. The power to the b/u switch comes from the pink wire in the two pin connector just inboard of the master cylinder on the firewall. What I am attempting to explain is that because the gauges fuse blows, it does not mean that you have a problem with your fuel gauge circuit. In your original post it sounds like you have a 4a fuse in that circuit and that won't work.

Vettegeezer

One of the "surprises" that I found after I bought my '67 and got it home was the very problem you are having. Long story short, found that the variable resistor windings of the fuel sender unit in the tank were fried. Made me wonder why the tank didn't blow up! Quick check is to see if the "S" terminal on the sender is grounded, if so you will need to pull the sender for inspection.

426 Hemi

Good point Frank. My dad's '64 had that wire pinched and shorted in the door sill area. Can't remember if it was pinched by the wire cover or the actual door sill (Bubba install). Also the end of the wire cover is very sharp where the wire comes out. I usually cut a little piece of Pinch Welt and put it over the raw edge.

426 Hemi

Dan, thought I'd add this to go with your Wilcox schematic. It's from the shop manual:

stmyrick

The fuse I'm talking about is the one at the tank which connects to the sending unit.
stmyrick

stmyrick

the fuse I'm talking about is at the tank, attached to the sending unit.

stmyrick

LB66383

?????????. I'm sure others will chime in, but I have never seen a fuse attached directly to the sending unit. All of the fuses for the car are in the fuse box under the dash. I assume you have some type of in-line fuse in the wiring attached to the sending unit? If so, someone has be messing with the wiring sometime in the past.

65GGvert

It's been added.

stmyrick

Weird; as I look again there is indeed a splice to the red wire going to the sending unit that has a "twist off" fuse holder for AGC fuses (the other 2 wires are just as they come out of the wiring harness. These in line fuses are the ones that keep blowing. Who knows what that's about! So what would be my best fix? I currently have the carpet out and the steering column freed up, as I'm also trying to troubleshoot the speedometer. Would there be a way to "rewire" the gas gauge; how would I run the wire?
Appreciate any advice.

426 Hemi

Looks like something is blowing the inline fuse on the sending unit side. The sending unit winding should only draw maybe a little over a tenth of an amp. You're blowing 4A fuses.

If it was me I'd source a quality repro sending unit and install. Easy if you get the tool.

stmyrick

Where is the sending unit? It's not a replaceable part?

I wonder why someone in the past fixed the problem by putting a fuse in the circuit next to the tank sending unit. This fuse didn't blow for the first 4 years I drove the car.

65GGvert

Inside the gas tank. It's replaceable

65GGvert

Your first check should be to see if the 12 volt wire going to it is shorted at the sender connections

Frankie the Fink

Correct ! As I said in post #3...

The fuel sending unit is in the bottom of the tank....I seriously doubt its bad -- here are some tests to check it..

Avoid replacing the sending unit if you can - it means draining all of the fuel and the reproductions are not all that great...
There is a person that will rebuild original sending units if it IS bad though...

Gary D. Jaynes

Vettegeezer

I agree 100%, see the archives on this topic. John Wolf & Co., Inc. rebuilt my original unit and did an excellent job. A little bit more than what a repro. unit will cost, but you roll the dice when buying the repro.