Help with Instrument Voltage Reg. modification

-
66fyssh

66fyssh

Don't Stop Believin'
FABO Gold Member
Joined
Jun 22, 2013
Messages
8,306
Reaction score
9,750
Location
Fort Walton Beach, Florida
Hello all, I did the mod to replace the internal voltage regulator on my 66 barracuda to get my fuel gauge working again and it's giving me fits. I used the 7805, 5 volt out regulator. The first one used gave an out put of just over 8 volts. So, I bought another one to replace the first one and the same thing...I'm getting over 8 volts out. Any idea why?? Here's a picture of my modification, does anyone see anything I'm doing wrong? I appreciate your help!!
 

Attachments

  • Dash Pic.jpg
    38.1 KB · Views: 202
Hi,

I'm new here and haven't had time to write up an introduction but , I saw your posting on the voltage regulator. I'm a retired electronics engineer and have a lot of experience with 7805's. I'm sure it's not wired correctly but all the red wires in your photo make it hard to trace the wiring. PM me with your email address and I'm sure I can help you sort things out.

Also, a 66 might have the old instrument voltage regulator in the fuel gauge that has to be disabled.
 
There are plenty of write ups about bending little thingys for the "do it yourselfers" on the internet . Most popular comes from a vendor with "engineering" in their title.
The original mechanical limiter must be removed no matter were its located.
 
Thanks guys. Pete is helping me offline.

I found info here and another site on the modification. I took the fuel gauge apart and bent the arm on the original internal regulator out of the way.

decided to go with the 7805 and capacitor instead of buying the RT-Engineering all in one replacement. They wanted $50 for their's. I got all the parts for under $5.

I just checked it again and I'm getting 9.13 volts out of the 7805 regulator...it's suppose to be putting out 5 volts. It's strange that it happened with two different 7805's.

Pete has a lot of experience with the 7805's so I'm hopeful he'll help figure out where I went wrong!
 
I'll be swinging back up by Va Beach on next Monday or Tuesday coming back from Hatteras Island. If you don't work daylight hours and are still stick, I can stop by for a bit. (Another retired electronics guy....) PM me by Sunday eve if you need a hand.

BTW, first make sure that pin 2 (the middle pin) is really at ground (0V); if you have the cluster out and have not hooked up a temp ground, that may be your whole problem. Is the pin 2 actually to a ground point on the cluster?

What value of added electrolytic capacitor is being used on the output? Too large a value close to the output can cause instability. Disconnect it and see if that helps.
 
nm9stheham said:
I'll be swinging back up by Va Beach on next Monday or Tuesday coming back from Hatteras Island. If you don't work daylight hours and are still stick, I can stop by for a bit. (Another retired electronics guy....) PM me by Sunday eve if you need a hand.

BTW, first make sure that pin 2 (the middle pin) is really at ground (0V); if you have the cluster out and have not hooked up a temp ground, that may be your whole problem. Is the pin 2 actually to a ground point on the cluster?

What value of added electrolytic capacitor is being used on the output? Too large a value close to the output can cause instability. Disconnect it and see if that helps.
Click to expand...

Thanks for the offer nm9stheham, Pete in NH sent me a diagram that made it very clear that my my input/output leads were reversed. I checked it and checked it against the sites I found online but until I had the diagram next to the dash on the bench, I couldn't see my error. It's great to finally have a gas gauge!!! :cheers:

By the way, my wife and I were married at the Oregon Inlet in Nagshead 16 years ago. I was stationed in Arkansas at the time and we planned a vacation there with friends of mine. I thought it would be the perfect place to say our vows. We were standing barefoot in the sand right at the edge of the water! Since moving to Va Beach 3 years ago we'll gone back for our anniversary every year. Great place! Oh, and I'm originally from Waynesboro, but the one in Pennsylvania and not Virginia!!

Thanks everyone!!
 

Attachments

  • Dash Gas Gauge.jpg
    40.7 KB · Views: 142
Good deal; glad it was that easy. Well, I am setting in a house in Salvo right now about 20 miles south of Oregon Inlet. (Just replaced a window damaged by Arthur.)

And good deal on Waynesboro PA; my wife's family is from there, and I lived on South Mountain (yes, with that rowdy bunch!) for 1-1/2 years. I street raced in Chambersburg in the 70's when they would let you get away with that.....what a crazy deal that was!! Small world!
 
Dang, small world indeed. Yep, you're right about the rowdy bunch on South Mountain!

When I was a Senior in high school, I bought a Toyota 4X4 and spend many, many days and nights all over South Mountain. Used to hang at "Valley View" on Oak Rd. I was just young enough to miss those days in Chambersburg; graduated Waynesboro High School in 81.

My wife would move down to OBX today!
 
I've used a 7805 regulator for years so I'm guessing you've got it wired wrong. There's only 3 terminals - 12v in, 5v out and ground. Be sure to use a heat sink too. Go online for pinout of the 7805, it's pretty straightforward. I also add a tiny LED to the output to know when it's on and I usually test the whole dash setup on the bench before wrapping it all up.
 
You must log in or register to reply here.
-

Back
Top