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I might be completely in left field here, but - I bought a new very early 77 in September of 76 and I seem to recall that the early cars didn’t the low fuel light. However, the lens was in the center cluster.
Edit - I found this in the Corvette Black Book regarding the ZX2 convenience group.
Low fuel light was part of the optional convenience group. Which included the underhood light and a few other bits and bobs. And from what I've seen that group seemed to change with what was available on the day. As my car has most of the list but never came with a mirror on the passenger side sun visor. But does have a low fuel light.
Bottom line. Not all 77's came with a low fuel light.
The board isn't a timer, but none the less is mounted on the backside of the guage cluster.
I have a 77 and everything on it works except the low fuel light. If it does work I don't know how low fuel gets for it to engage as I've run mine below empty for 20 miles and it doesn't come on. Mine doesn't have an under hood light or passenger mirror
If you don't have the underhood light, you most likely don't have the convenience group. A few years ago someone posted on here the list of what was included. My car came with everything on the list except the mirror. Others over time on here have posted one thing or another missing on their cars. But no one seemed to be missing the underhood light. That is those of us with the factory convenience group.
My low fuel light comes on a bit late compared to other vehicles I have owned. But certainly comes on before the guage hits empty. Not much before mind you. But certainly comes on before the needle hits the E.
To see if your car actually has this option, pull the center guage cluster and look on the back side. I looked to see if I had a photo of this from when I rebuilt my guage cluster just a few weeks back. But no, no photo.
Just to add to what others have posted, The 3rd edition of the NCRS 1975-77 technical manual (published last year) doesn't address low-fuel but does mention that the spare tire lamp was not included until mid production. Here's the statement:
In 1977, a spare-tire lamp was incorporated into the RPO ZX2 convenience group but did not begin production until mid- to late-built Corvettes. Among cars surveyed, those before VIN 25051 (March 2) were not equipped with the light, and the earliest found is VIN 32293 (April 26). Some variations in this timeframe should be expected.
There is no reference to early 77s not having the low-fuel lamp, which doesn't mean it did not happen...the revision team may not have had access to early 77s with the option and it did not work. In 1978, a low-fuel lamp comes on at approximately five gallons...I've tested it numerous times but then in 78, the tank capacity increased from what 17-19 gallons to 24!
Like I said, seems to be some variations in the convenience group option, But none the less. The low fuel light was part of that option.
It was a option, Not standard equipment.
The lens would still be in the center cluster none the less.
But the board and bulb wouldn't be there if the option wasn't ordered.
No under hood light, no low fuel light.
My guess, the OP's car didn't come with it.
Me, I am certainly glad mine did. Low fuel lights were invented for guys like me.
However, if the OP wishes to add this feature. Shouldn't be too hard.
It is my understanding the Low Fuel Light module was not available yet when production started for the 77.
It is also my understanding a credit was applied back to the buyer something like $8.00 at the time.
In my 77 the light came on just after I added the 3rd gallon when the tank was completely empty.
You can add a LOW FUEL light module to any 77 and later, the circuit is already wired for it.
My LOW fuel module stopped working sometime in the 1980's...
A few years ago I pulled and tested it, found a bad transistor then researched a replacement...
About a $3.00 repair and my time the module functions as it should again...
Thanks Dan
I can purchase board module and can understand timer circuit for light but how does it know when fuel is low?
It does not look like it hooks too fuel gage at all, unless I am not seeing everything.
once again thank you
It might be helpful to get a perspective on the complete circuit...from the tank and the fuel sender unit to the board and gauges and low-fuel light. This article illustrates the fuel tank sending unit and shows the mechanical potentiometer that notifies the PCB when fuel gets low.
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Originally Posted by hunt4cleanair
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In 1978, a low-fuel lamp comes on at approximately five gallons...I've tested it numerous times but then in 78, the tank capacity increased from what 17-19 gallons to 24!
That's disappointing news!😄 I have seen the Low Fuel Light come on in my '78, a long time ago, and when I knew it was pretty low on fuel. However, a month ago we opted not to refuel on the Autoroute while returning from a run up to Paris and back, due to the high cost on the Autoroute stations. So, we "bit the billet" and carried on, eventually managing to reach our usual fuel station near home. making a total mileage for the morning run of 266 miles on a tank full. The car took just over 70 litres to fill. The '78's 20 US Gal tank equates to 75 litres, so we were pretty low! But, no Low Fuel Light that I saw😟 Maybe the sun was in my eyes or on the cluster?! I doubt we'll ever get that low again, but if we do, I'm going to have to be more aware of the light!
But, no Low Fuel Light that I saw😟 Maybe the sun was in my eyes or on the cluster?! I doubt we'll ever get that low again, but if we do, I'm going to have to be more aware of the light!
Typically, it comes on softly...not quickly than fades out. But returns in full glow. I would run around town just to test it...but never on the autobahn! That's bravery.
