Ralley dash gauges

[Jamie Hassell]

I bought a 67 barracuda roller project, added a 340 4sp with an 8.75, I bought factory replacement wiring harnesses for engine compartment and under dash (previous owner made his own) replaced the circuit boards on the back of the dash along with a ivr that the previous owner had installed on the back of the fuel gauge (radio shack), I did look in side the gauge and he did have the little 12v supply wire cut off but did not disconnect the intermittent contactor like I’ve read to do. When I turn the key on it shows 5v on the power side of all the gauges but the needles do not move when it’s running. Independently if I ground out the sender wire the needles all move so I’m assuming the gauges are working and oddly enough it must be all my sending units so I replaced them all with new ones with the same result, I ran a made up ground wire from the dash which isn’t installed (just siting in place) directly to the battery still nothing, anyone have any idea what I’m doing wrong?

 

[Murray]

Is the cluster/circuit boards grounded?

 

[Jamie Hassell]

They get screwed into the metal structure of the dash then I ran a ground to the battery but saying that some of the dash light grounds needed to be massaged to get the lights to work

 

[4spdragtop]

Not sure what the issue is, BUT these gauges (our 67 also) are 60 yrs old. Do you want to be doing this again? Add a triple gauge set and leave gauges as cosmetic. We did that with our 67.

 

[Jamie Hassell]

lol, yes I’ve thought about it more than once but this problem is beating me up, I’m sure with some help I’ll get it figured out

 

[Mattax]

Have you read the information on how to test the gages?

 

[Jamie Hassell]

Not these gauges specifically, I just powered up with the key (5v) and grounded out the sender wire briefly to see if the needle moves which it does on each gauge, is there a different way?

 

[Mattax]

In the shop manual and in the MTSC.
(Note the 67 Service and Parts manual was released before the 67 Barracuda information could be added, so for most editions thats a supplement)

These are thermal gages.
1. Do a resistance test
There should be around 20 ohms resistance. If its in spec, great, time to see if they work. (For the ammeter, there should be zero resistance. Touch the probes together first - that will be the zero. Physically check ammeter. If the studs are tight and no measurable resistance, then its probably OK.)

2. For the thermal gages. These can be driven with a couple of C or D cell batteries in series. This will reveal if they work. That's a fairly safe check.
Even better yet if they are on the bench, get yourself some 11 and 22 ohm resistors or a variable resistor (potentiometer) and a 12 - 14 volt power supply (a car battery will work fine). Use jumpers to hook up the gages to the resistors. Power the Instrument Voltage regulator in the fuel gage in test.
DO NOT GROUND the gages. Without the resistance in the sending units, the resistance wire in the gages will overheat.

This post will get you further

Rallye Instrument cluster voltage limiter - 68 Barracuda

I recently did reworking of the gauge cluster to replace lights in my 1968 Barracuda, and replace both of the circuit boards with ones from Classic Industries. Everything worked fine for a while after, until the temperature, oil pressure, and fuel gauges started going strait to max travel with...

www.forabodiesonly.com

If the IVR is showing steady volts output then someone has installed an electronic version.

 

[Woodys_Cuda]

If I read this right. Was looking at this thread and and looks like the problem is in the "run" position which leads me to believe the IVR does not have a 12 volt source in that key position. Recheck the wiring?

 

[ESP47]

You're on the right track. Get yourself a 100ohm potentiometer (cheap) and set it to 23ohms. Put that in series when you test your gauges to ground so you don't damage them. The needles should go to halfway at 23ohms if they're somewhat accurate.

Is your gauge cluster installed in the dash or is it just kind of hanging in there so you can get to the back easily? Maybe run a jumper from one of the screws in the back of the cluster to the dash and then leave your jumper from the dash to the battery ground connected. Do an ohm test from each point to make sure you have continuity.

 

[Jamie Hassell]

Sorry for the late response I’m on the road for a few more days

 

[Jamie Hassell]

I started by grounding the sender wires briefly with the key on and the needles moved towards the max, then I bought another new fuel sending unit and hooked up the sender wire to the post on the fuel sender and grounded the sending unit then moved the float up and down, I did this to fuel then temp and oil separately and could make all the needles move and settle anywhere with the movement of the float, (the oil pressure gauge did seem to take 5/10 seconds before it starts to move, not sure if that means anything or not), this is when I figured I had the wrong sending units (maybe for idiot lights)replaced oil and temp and still no gauges working

 

[Jamie Hassell]

I started by grounding the sender wires briefly with the key on and the needles moved towards the max, then I bought another new fuel sending unit and hooked up the sender wire to the post on the fuel sender and grounded the sending unit then moved the float up and down, I did this to fuel then temp and oil separately and could make all the needles move and settle anywhere with the movement of the float, (the oil pressure gauge did seem to take 5/10 seconds before it starts to move, not sure if that means anything or not), this is when I figured I had the wrong sending units (maybe for idiot lights)replaced oil and temp and still no gauges working

Forgot to mention the dash isn’t screwed down (worried it with have to come out again)but I did run a ground from one of the screws that go into the metal portion of the cluster all the way to the battery neg.

 

[Jamie Hassell]

Up date, checked that I had 20 ohms across the A and S posts on all the gauges then I hooked my spare fuel sending unit to my meter and marked on it where approximately 25 ohms was then hooked up to my gauges that weren’t working and still nothing till I moved the float to where the meter was around 15 ohms then the gauge moved to 1/8th on the gauge then to 10 ohms and barley went to 1/3 tank and would still go to high on the needle if it was directly grounded. Luckily I had another dash and did the same to those gauges and at 25 ohms was getting mid or more movement on the needles. Changed out the gauges, installed into the car, fired it up and they all work! The original gauges were over heated enough they didn’t work accurately, they worked with little to no resistance but not off the sending units. Thanks for the help guys!