Fuel gauge/ tension cables

[Wilregul8]

Hi all,
I own a 1970 De ville convertible. When I turn the lights on my fuel gauge goes down to empty . It reads the proper fuel  level when the lights are off though. Anyone ever have this issue?  Also can anyone explain the purpose of the tension cables in the roof rails?  I can only imagine they provide a little more stability. I recently had the top replaced but the installer told me I  didn't really need them.

[Cadman-iac]

If you're referring to the small approximately 1/16" diameter cables that run along each side from the front to the rear,  those help keep the edges of the top from flopping in the wind, and keep it tight from left to right when the top is up.
I don't know who you're using to install the new top, but you might want to double check his credentials.
I've had 5 convertibles, one was a 69 Cadillac,  and those cables are definitely necessary.

Rick

[The Tassie Devil(le)]

Those cables are definitely for stopping the sides from flapping around.

Plus, they hold the sides tight and assist in controlling shrinkage to a degree.

Bruce.

[Cadman-iac]

 Those cables give the top the nice flat sides over the glass. It helps keep the material covering the weatherstrip that seals the windows to the roof rails. And without them, the top would curl up over the glass and give it the appearance of having drip rails if it got really bad. Not a good look for a convertible top. You want nice crisp lines on the sides, and those cables give you that.

Rick

[Big Fins]

Without those cables, you'll be riding down the road at 40 mph+ and the top fabric will lift up and it will be just like having the top off in the rain. You WILL get wet. As will all of your door mounted switches and inner door items too, such as lock actuators and window motors.

[Jeff Rosansky CLC #28373]

When your lights are on your voltage drops. The fuel gage is voltage sensitive. When the voltage drops, so does your gauge. You have an electrical/charging issue,  not a gage issue.
Jeff

[Wilregul8]

Thank you all for the advice. Jeff you are on the money with the charging issue! 🖒 I noticed today that the gauge goes up and down depending on the position of the dimmer switch. Thanks again.

[bcroe]

I think your gauge problem is a bad gauge ground wire.  So the gauge
finds a ground path through the lights (that are grounded) until you
turn them on, changing the voltages.  Bruce Roe