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1966 coupe and 1970 sportsroof
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Discussion Starter · #1 ·
A while ago I was having a gauge twitch problem.

http://forums.vintage-mustang.com/forums/showflat.php?Cat=1&Board=forum&Number=399111&page=&view=&sb=&o=&fpart=all&vc=1

This has now escalated into the guages hardly working at all! Fuel, temp and oil barely twitch from the left side of the gauge. I've checked all my grounds and 'wiggled' the wires behind the dash, nothing.

One weird thing though is when I drive in hot temps like 85+ degrees, they work, but still twitch like they used to, but they work. As soon as it cools off, they swing to the left and barely twitch.

Whatever the problem is also drains my battery flat within 24 hours if I leave the + side connected...

Battery and alt are new. I was going to start throwing money at it, replacing the instrument and voltage regulator but they are both getting to be around $30 each!

Any other suggestions?
 

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367 Posts
none of the electrical stuff guages, dash light, turn signal light, or radio will work half the times I start it up. I figured out that there is a notch between start and on, on the key. You have to make sure it goes all the way back to on and not halfway between start and on.
I hope this helps some, I plan on taking a look and trying to fix it tonight when i get home, after I wash my baby!
 

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Your constant voltage regulator is about to go out or is not properly grounded. Oil, fuel, and water gauges all run off of it.
 

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1966 coupe and 1970 sportsroof
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Current cars include 1969 Mach 1 and 1970 Cougar XR7 convertible
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Shaun:

That's the instrument one inside the dash. It's got my vote as well. The battery drainage issue has got me stumped though. It could be anything and diagnostically disconnecting circuits one at a time until the "leaking" circuit is found is the best way to isolate an electrical problem in a 35+year old car.
 

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1966 coupe and 1970 sportsroof
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Easy. Start by removing fuses, one by one, with the battery disconnected. Use a volt-ohm meter that can measure current, and measure the current between the negative post of the battery and the disconnected cable. Should be 35 milli-ohms or less. By removing fuses, you should be able to isolate the circuit. If not, remove the wires off the solenoid battery post one by one. Also, disconnect the voltage regulator. One of them will isolate what's drawing the current.

Don't forget to turn off the lights and close the doors while you do these tests! *G*
 

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1966 coupe and 1970 sportsroof
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5,357 Posts
Discussion Starter · #8 ·
I think I can follow those instructions! Thanks!

I did just mess around with the instrument regulator. It seems by moving one of the connectors left and right, I can get the fuel gauge to respond with the key in the on position. I checked all the connections, looks good. You still think it's the regulator and not a connector?
 

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Vendor
1966 coupe and 1970 sportsroof
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5,357 Posts

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Vendor
1966 coupe and 1970 sportsroof
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5,357 Posts
Discussion Starter · #12 ·
$14 from where? I've checked NPD, Mustangs Unlimited and Mustangs +, they all charge $30!

$14 is a no brainer, where, oh where might I find one so cheap?
 
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