Gauge voltage and Fuel relay with AA classic install

-
clementine

clementine

Flight risk
FABO Gold Member
Joined
Jan 3, 2016
Messages
3,097
Reaction score
2,620
Location
Emerald city
Hellllllooooooo FABO electrical wizards!!!

I have never totally wired a car before so bear with me please.

1967 Barracuda Fastback rallye dash/gauges/American Autowire 'A body classic kit'

Question #1
When I tested guages I used 3 AA batteries to check sweep and check weather the things were gonna register anything. Now they are in the car and Im thinking to myself as I look for good grounds for everything.....where does the voltage step down for the gauges? If there is something I am supposed to splice into the power feed to gauges....what does it look like?

Question #2
Holley Sniper EFI in the same car. There is a 12 gauge blue wire with a relay and fused located about at the firewall that runs to the fuel pump located around the axle. So, give or take around 6' of wire. I was always told to run the relay as close to the unit that was going to be powered up. I have a universal summit fuel relay handy and it has a little metal box fuse looking thing that comes with it. My super safe voice in my head says "Hey Clem, go ahead and use that blue 12 gauge wire marked 'fuel pump' and trigger a relay real close to the pump". This car has the battery in the trunk so everything is in close proximity for this situation. Do the voices in your head concur?

Thanks FABO!!!!!
 
Maybe this goes inline? somewhere?
20211104_103714.jpg
20211104_103722.jpg
 
The voltage regulator originally for 67 cuda was in the fuel gauge. That is the factory "step down" . The napa one you have I believe is for NON rally dashes.
 
4spdragtop said:
The voltage regulator originally for 67 cuda was in the fuel gauge. That is the factory "step down" . The napa one you have I believe is for NON rally dashes.
Click to expand...

So since I am running a factory fuel gauge, I should be fine. I will suss out my grounds and when I go to turn the key Ill keep an eye out for the gauges pegging and abort mission if I see excessive current....or is there a better test?
 
Any time I've "tested" gauges, I used a 6v lantern battery and tested for needle movement individually. I've never tested with 12 v and thru ivr/fuel gauge.
I'm an idiot when it comes to elec.voodoo(and more lol)
@67Dart273 , @RedFish and @Mattax @moparmat2000
Can help you out. Just my opinion, BUT you've gone this far....use an external VR and clip the internal one. 55 years old. Its had a good life lol.
clementine said:
So since I am running a factory fuel gauge, I should be fine. I will suss out my grounds and when I go to turn the key Ill keep an eye out for the gauges pegging and abort mission if I see excessive current....or is there a better test?
Click to expand...
 
4spdragtop said:
Any time I've "tested" gauges, I used a 6v lantern battery and tested for needle movement individually. I've never tested with 12 v and thru ivr/fuel gauge.
I'm an idiot when it comes to elec.voodoo(and more lol)
@67Dart273 , @RedFish and @Mattax @moparmat2000
Can help you out. Just my opinion, BUT you've gone this far....use an external VR and clip the internal one. 55 years old. Its had a good life lol.
Click to expand...
Pretty solid advice.
 
You cannot really measure the gauge supply voltage because the original "regulator" is a pulsating deal like a turn flasher. The gauges react so slow that they do not show the flashes. Seems to be "equivalent" to 5-6V

The way to check them is supply 12V to the proper cluster connection, and put known resistor at each of the gauge sender terminals. They should all read the same with same resistance.

If the cluster is out, or if you are inclined to take it out, I'd "go through" it. Check/ repair the harness connector pins on the circuit board, add a grounding pigtail from the cluster, and loosen/ tighten the gauge stud nuts (or replace nuts) to "scrub" the PC traces clean where the nuts bite, and clean the lamp sockets and board etc etc.

If you can now would be a good time to replace the instrument regulator with a solid state one. This is a bit of a trick, as you have to disable the one IN the fuel gauge, mount the new one externally, and then jumper power in through one of the gauge studs. The gauge has a 12V power in stud which feeds TO the IVR, 5V "out" stud which feeds the regulator output to the other gauges. THAT is where you jumper the 5V INTO that stud to power the fuel gauge. The 3rd is of course the sender terminal

c-3826-jpg-jpg-jpg.jpg
 
Last edited:
A relay location does not need to be close to the load, so long as the wire from the battery and to the load is large enough to supply it. If the battery is in front, and the pump in rear, it makes no difference which end of the car it is located

If both pump and battery are in the rear, it would make sense to relocate the relay. You don't need to add one, you can abandon the one there, and install it or a different one in the rear, then just extend the trigger wire from the supplied one

If both the pump and battery are in the rear, it makes sense to move the relay, because now you have to have adequate power wire all the way from the battery (or the battery main wire) from the trunk, and then run it right back all the way to the trunk
 
Thanks @67Dart273 and @4spdragtop! I just came upstairs from wiring in a relay that is back by the pump. I haven't taken out the 'factory' Holley one, but will....maybe. May just leave it. Im trying not to cut up the wires so if (when) I do have a problem I can diagnose easier.

I did go through the gauges before putting in the dash and have new printed circuit boards (that I tested), so things are pretty new under there including ALL the wiring. Ill probably swing out the dash though and see if I can service that fuel gauge. It shouldn't be that big of a deal since the windshield is out and the frame is held in by two bolts at this time. I did flip the 'catch nuts' and will be fastening the dash frame from the underside in case there is a future need to access/remove dash.

Ill probably have to check in with you to decipher your words or just re read. Im pretty tired from a day of wrenching. gettin old. Painted the wheels on Heidi's truck and put new rubber on them, combined with finishing the fuel pump access hole and wiring up the relay took waaaaaay more time than expected!
 
If I hadn't been tagged in this thread I wouldn't have posted at all. The folks at real time engineering published info about opening the 3 post gauges to physically disable the internal limiter. Since they are e-body people and dnot know, they did some research. They found what a man named Erinburg or something like that had published on the Imperial website ( He was on about a limiter inside the temp gauge instead of fuel gauge, not that it makes a difference which gauge they put it in). Anyway... Over the past few years I have attempted to explain, It is not necessary to remove a gauge cover and bend something to isolate that mechanical limiter and substitute a solid state regulator. All that you really need to do is 2 steps... Lift the 3 post gauge and cover a slither of metal on its back side with electric tape to isolate it from chassis ground like any 2 post gauge is isolated from chassis ground.
Since the switched 12 volt wire to the limiter in the fuel gauge serves nothing more in the inst' panel (blue with white tracer), back it out of the round harness and route it to whatever solid state regulator mounted anywhere you want. Route the substitute regulators 5 to 6 volt output to anyone of the traces on circuit board that carries that current and you are done. Alas...
There was one owner/member here who tried to blend what I detailed with what he had read online. Rather than move the wire out of the round connector, take the 12 volts away from the fuel gauge, he jumpered from that gauge post. Both mechanical and solid state got 12 volts at switch on. That chit didn't work. His subsiquent posts wadded my panties up. LOL
At that point, I gave up. Bottom line, Good luck with it.
 
I like Redfish's IVR instructions above. Can anyone post pics to go along with this? Showing which wires go where on the IVR and then back to the circuit board, etc. Would be a good permanent 'Sticky'.
 
Any IVR you get should be marked 12 volt in, 5 volt out, and ground.
On back of inst' panel, the round harness connector has a locating key in its center. Fuel gauge wire is always dark blue and in this case, directly above the key at 12 o'clock. The switched 12 volt wire feeds nothing more than the OEM limiter. It is blue with white tracer and at about 9 o'clock position of round connector. It will go directly to your IVR no matter where you decide to place it.
One copper trace on the board ties all 3 thermal gauges to the 5 volts. You wont have a wire color or trace from round connector to here. 5 volt output from your IVR can go to any one of these 3 gauge posts. Circuit board does the rest. I use ring terminals, 10-32 hex nuts and a toothed washer on top of the original speedy nut for secure connections to gauge posts.
A solid state IVR doesn't require the noise capacitor so removing it provides a 90 degree push on terminal with short lead that you could use for 1 of the connections. I save those terminals for other uses since its a #10 and nearly impossible to find.

rally panel circuit board.jpg
 
Perfect. Thanks RedFish. This would be a great electrical tech 'sticky' since it seems to come up frequently.
 
mrhp said:
Perfect. Thanks RedFish. This would be a great electrical tech 'sticky' since it seems to come up frequently.
Click to expand...
Yeah, a lot of members go to some degree of effort to create "how to" etc... That aint me. A lot of what I consider the best or simplest way to do something goes against what someone else has published online, long before me and they get all the traffic (that is how the internet plays.)
Maybe because they have "Engineering" in their title, it has already proved futile try to discount what they suggest (I did play their game for 8 years). You could look at RTE webpages and follow what they advise. Open you fuel gauge and bend some thingy if you want. That method to the madness works too. Ignoring me doesn't bother me.
My plan is happy moparing to all owners. I know how my own rally instrument panel works flawlessly. The three thermal gauges work, amp gauge is now a volts gauge and that works fine also. It should for many years to come.
During that 8 years, not only did I have a fuel gauge exchange program. It snowballed into owners sending me entire inst' panels to mod' to be just like mine, solid state regulator, volts gauge and all. I never heard the 1st complaint. I'm so proud of that. I'm retired today and doing nothing but typing. I'll be here to help you anyway I can.

DeMonDIN plus burl 01 resize.jpg
 
RedFish said:
Yeah, a lot of members go to some degree of effort to create "how to" etc... That aint me. A lot of what I consider the best or simplest way to do something goes against what someone else has published online, long before me and they get all the traffic (that is how the internet plays.)
Maybe because they have "Engineering" in their title, it has already proved futile try to discount what they suggest (I did play their game for 8 years). You could look at RTE webpages and follow what they advise. Open you fuel gauge and bend some thingy if you want. That method to the madness works too. Ignoring me doesn't bother me.
My plan is happy moparing to all owners. I know how my own rally instrument panel works flawlessly. The three thermal gauges work, amp gauge is now a volts gauge and that works fine also. It should for many years to come.
During that 8 years, not only did I have a fuel gauge exchange program. It snowballed into owners sending me entire inst' panels to mod' to be just like mine, solid state regulator, volts gauge and all. I never heard the 1st complaint. I'm so proud of that. I'm retired today and doing nothing but typing. I'll be here to help you anyway I can.

View attachment 1715826663
Click to expand...
RedFish said:
If I hadn't been tagged in this thread I wouldn't have posted at all. The folks at real time engineering published info about opening the 3 post gauges to physically disable the internal limiter. Since they are e-body people and dnot know, they did some research. They found what a man named Erinburg or something like that had published on the Imperial website ( He was on about a limiter inside the temp gauge instead of fuel gauge, not that it makes a difference which gauge they put it in). Anyway... Over the past few years I have attempted to explain, It is not necessary to remove a gauge cover and bend something to isolate that mechanical limiter and substitute a solid state regulator. All that you really need to do is 2 steps... Lift the 3 post gauge and cover a slither of metal on its back side with electric tape to isolate it from chassis ground like any 2 post gauge is isolated from chassis ground.
Since the switched 12 volt wire to the limiter in the fuel gauge serves nothing more in the inst' panel (blue with white tracer), back it out of the round harness and route it to whatever solid state regulator mounted anywhere you want. Route the substitute regulators 5 to 6 volt output to anyone of the traces on circuit board that carries that current and you are done. Alas...
There was one owner/member here who tried to blend what I detailed with what he had read online. Rather than move the wire out of the round connector, take the 12 volts away from the fuel gauge, he jumpered from that gauge post. Both mechanical and solid state got 12 volts at switch on. That chit didn't work. His subsiquent posts wadded my panties up. LOL
At that point, I gave up. Bottom line, Good luck with it.
Click to expand...

I really like this idea better than opening up the gauge, but I have a question if I may. The blue with tracer wire doesn’t show as going to the fuel gauge on my wiring diagram. It shows going to the oil light in dash. A black wire goes to the fuel gauge. Can you please confirm which wire? Thanks
 
You must log in or register to reply here.
-

Back
Top