Rallye cluster gauge issues - 67 Barracuda

[67fish383S]

I imagine this topic has been covered many times before, and I suspect I already know where to start looking for my problem, but am looking for some shared wisdom. I did some searching of older threads and found several related posts, but nothing that fits my situation exactly. I apologize in advance for the wordiness to follow...

Here is the back story: I recently had the cluster out of the car to replace the vacuum gauge with a tachometer and upgrade the cluster lighting to LEDs. Prior to pulling the cluster, I bought a discreet voltage limiter because one was shown in the service manual mounted to the rear of the cluster, but found out later that in the rallye clusters, the limiter is built into the fuel gauge. I considered holding off on re-installing until I could do a solid state upgrade, but didn't have parts or a lot of info on it, so I stupidly plowed ahead and re-installed the cluster after bench testing all the LEDs.

Everything was great for a little while. All the existing gauges worked fine, the new tach was spot-on, and all the lighting was good. Cut to yesterday on my way to a car cruise...noticed the fuel, temp, and oil pressure needles all at zero. Dammit. Tach still working fine and all the lights were good. Immediately thought check the fuse (good of course). Then thoughts turned to the damn limiter or perhaps a loose connection or flaky solder joint in the cluster. Continued on the cruise having a full tank of fuel. A little while later, gauge function came back. Noticed the fuel needle 'wandering' a bit, but everything else seemed normal. A while later all dead again. By the time I got home, the tach was now effed up. Not completely dead, but the needle was below zero and not moving much.

The new tach has three connections: +12V, ground, and tach signal wires. I took the 12V off the blue wire at the ignition switch, because this had been previously tapped for the after market tach I was replacing, but thinking about it now, that was probably for the backlight. The old one got power from the fuse box. I ran the new tach ground to a screw on the dash frame.

So those are all of my symptoms. I still suspect the voltage limiter, but now wonder if the new tach wiring may be hosing the situation somehow. I really, really, don't want to pull the cluster again, but it seems like I won't be able to avoid it. If/when I do pull it again, I will go through all the connections and re-solder any pins/traces that look like they need it (what I should have done the first time).

Wondering if anyone has thoughts or suggestions. Also want to know more about how best to upgrade the limiter/fuel gauge situation. Please help. I am so tired of being folded like a pretzel under this dash lol.

 

[moparmat2000]

Unfortunately you need to dissassemble the face from the fuel gage and disable the built in IVR while leaving the part of the gage that works the fuel level needle alone. I used a small pair of miniature wire snippers to carefully unroll the edges and slide the face off. Mark the back of the gage face and gage housing in one spot so you can re crimp it back together in the same place on reassembly.

Your new IVR will mount on the exterior of the back of the instrument cluster. Why chrysler elected to mount it inside the gas gage on this type of gage panel is beyond me. The first pic says to remove the small black insulated wire, but also clip off and remove the bimetal point contactor that has the bare wire coil wrapped around it. Leave the 3 studs on the back of the gage as one is your tie in for the 12V feed, and the other is your 6V output, along with a ground. The remaining 3rd stud coming out of the gage not mentioned in my diagram is your sense wire that goes to the fuel sending unit. I also ended up threading in a stainless steel stud in the location shown as a dedicated ground.

The solid state chip you need is an NTE960 along with a small capacitor and will require come basic solder skills. See schematic and pix below. The NTE960 will take up to 35VDC input and drop it to 5.5VDC output. So running 12-13VDC through it is asking really nothing of it in the grand scheme of things. My wire color coding is red for 12V input, yellow for 6V output, black for ground. I was making these for awhile and selling them but this is a nice DIY weekend project.

(Note in the schematic it shows 2 grounds. The wired ground to the cluster, but also the chips mounting tab. The mounting tab is the second ground and must be grounded for the chip to work)

 

[moparmat2000]

You should ditch the Ammeter and convert it to volts while in there. I did that with mine. Requires a sun volt gage, 1 small jumper wire, and you tie your 2 ammeter wires together and stick em back in the harness.

 

[67fish383S]

You should ditch the Ammeter and convert it to volts while in there. I did that with mine. Requires a sun volt gage, 1 small jumper wire, and you tie your 2 ammeter wires together and stick em back in the harness.

Sounds like a great idea. When I realized they routed all power to the car through the ammeter, well I'm still shaking my head. Does the sun volt gauge you mentioned replace the existing amp gauge in the cluster, or is it mounted remotely? Do you have a link or a part number? Thanks again. I really appreciate the wealth of knowledge in this group.

 

[moparmat2000]

Replaces it. I'm headed to work. But heres a pic of it. Notice it's on full discharge with no power going to it.

 

[RedFish]

you said you checked a fuse. There isn't a fuse other than the fusible link. 2 of blue with white tracer in one terminal at your ignition switch. One goes through the firewall to feed the charging system voltage regulator. The other goes to the round harness connector on inst' panel to feed gauge voltage regulator.
About the post above that shows opening the gauge and disconnecting the 12 volt supply to the limiter. It doesn't say anything about this gauge with limiter being chassis grounded. So assuming the limiter still has continuity through it, The 5 volts supplied by another source will back feed through that limiter to ground. So that limiter is wicking away some portion of the 5 volts, as if it were a 4th gauge.
No one even needed to open a gauge to disable a limiter. Simply lift the gauge from the housing and cover the small piece of metal on its backside with electric tape to isolate it from ground. Take the blue with white tracer out of the round connector and route it to any substitute regulator mounted anywhere you like. It doesn't have to be on the back of the inst' panel.
The unit from Real Time Engineering is the one to buy. It costs more but... it includes ground fault protection. That little 7805 chip does not. If it looses chassis ground, 12 volts goes straight through it and out on the wire that should be only 5 volts. That will fry all 3 of your gauges. The RTE unit has LED indictors on it so may as well mount it where they can be seen. Nowhere to mount it on the back of the rally panel anyway.
A guy named Rick Erinburgh (or something like that) first published this "open the gauge" procedure to a Imperial website about 20 years ago. He hadn't look at it close enough. Then others propagated that info without doing their own study.
In the end, I hope you find only something simple,, a loose pin at the blue with white, or the fuel gauge is a little loose at its mounting nuts, limiter lost its ground, you didn't need any of this info.
If you do determine a substitute regulator is needed and you'll convert the amp gauge to a volts gauge... the blue with white should also feed switched 12 volts to the positive side of the volt gauge. You will need to add a ground wire to negative side of a volts gauge. There is a proper method to do that too.

 

[Mattax]

^^^^THIS^^^^
Read Redfish's post carefully, and take notes.

Let me explain why I so strongly suggest following Redfish's advice and why I so marked disagree on the earlier posts.
Redfish's explanation correctly describes the power flow, and why the RTE unit, if needed, is safer.

Now lets get to power flow.
When the engine is running all of the power should be coming from the alternator.
Power from the alternator does not go through the ammeter.
The only current flowing through the ammeter is current to recharge the battery. If there is a winch or plow wired to the battery, that would be an exception.
In spite of the fact that the ammeter is labeled 'Alternator' it only indirectly indicates alternator output.
What it really shows is current flowing to or from the battery. IF the battery is discharging during normal driving, you can assume the alternator is not working.

Why is this?
Because electricity always flows from the highest voltage power source.
The battery's power is available at 12.8 Volts give or take some.
The alternator's power is available at 14 Volts give or take some.

Here's a diagram showing normal current flow with orange arrows.

That little bit of current flowing down the accessory circuit is going to the IVR.
Specifically it goes through a welded splice to terminal at K on the connector. There is no fuse for this subcircuit.

If your Barracuda had been optioned with a tach, it was supplied 12 Volts from a fuse connected to the accessory buss in the fuse box.
I just recreated that for my car so I can show some photos in the next post.

 

[Mattax]

In the fuse box, the accessory feed is the black insulated wire with the flag terminal on the left

The empty slot was used for various optional accessories; tach, rear defroster, air conditioning.

It's not too difficult to get a new or used set of fuse clips and terminals.
You can buy new from Bill Rose - he uses steel ones made by AMP - or used from someone stripping a car. The easiest used ones to incorporate are a set of singles from the accessory slot or the instrument lighting slot (far right in fusebox photo).

Trial fit.

Jumpered from the accessory buss.

if you're only running the tach, the heavy gage wire I used is overkill.
Figured in case some future owner adds A/c or something better to go with the 12 or 14 ga.

For the tach power, I used some blue insulated TXL from Wirebarn.com General purpose wire would be OK too.
Used a marker to put a black stripe on it to reduce confusion with the factory ignition wires.

 

[Mattax]

PS. On my 67 Barracuda there was a ground wire from the capacitor mounting to the radio brace. It looks original but even if not, not a bad way to do it.

PSS.
Since Accessory also powers radio, turn signals, wipers, and heater fan, checking those will help isolate a loose or poor connection if that's the problem.

 

[moparmat2000]

My pic doesnt show it, but I also mentioned removing the bimetal point contact with the wire coiled around it so theres not a shunt to ground inside the gage. Paragraph 2

 

[RedFish]

My pic doesnt show it, but I also mentioned removing the bimetal point contact with the wire coiled around it so theres not a shunt to ground inside the gage. Paragraph 2

My main point was, There is no need to open the gauge. A typical 2 post gauge does not have a 12 volt supply and is not chassis grounded. A 3 post gauge has these 2 connections for the limiter. Simply remove those 2 connections from a 3 post gauge. it now works just like any 2 post gauge.

^^^^THIS^^^^
Read Redfish's post carefully, and take notes.

Let me explain why I so strongly suggest following Redfish's advice and why I so marked disagree on the earlier posts.
Redfish's explanation correctly describes the power flow, and why the RTE unit, if needed, is safer.

Now lets get to power flow.
When the engine is running all of the power should be coming from the alternator.
Power from the alternator does not go through the ammeter.
The only current flowing through the ammeter is current to recharge the battery. If there is a winch or plow wired to the battery, that would be an exception.
In spite of the fact that the ammeter is labeled 'Alternator' it only indirectly indicates alternator output.
What it really shows is current flowing to or from the battery. IF the battery is discharging during normal driving, you can assume the alternator is not working.

Why is this?
Because electricity always flows from the highest voltage power source.
The battery's power is available at 12.8 Volts give or take some.
The alternator's power is available at 14 Volts give or take some.

Here's a diagram showing normal current flow with orange arrows.
View attachment 1715598761

That little bit of current flowing down the accessory circuit is going to the IVR.
Specifically it goes through a welded splice to terminal at K on the connector. There is no fuse for this subcircuit.
View attachment 1715598762
This changed at some later model but in a 67 rally harness, K is blue with white. F is black. The blue with white was eventually deleted. The one black switched 12V feeds brake warning lamp, oil warning lamp, and the limiter.

If your Barracuda had been optioned with a tach, it was supplied 12 Volts from a fuse connected to the accessory buss in the fuse box.
I just recreated that for my car so I can show some photos in the next post.

 

[67fish383S]

you said you checked a fuse. There isn't a fuse other than the fusible link. 2 of blue with white tracer in one terminal at your ignition switch. One goes through the firewall to feed the charging system voltage regulator. The other goes to the round harness connector on inst' panel to feed gauge voltage regulator.
About the post above that shows opening the gauge and disconnecting the 12 volt supply to the limiter. It doesn't say anything about this gauge with limiter being chassis grounded. So assuming the limiter still has continuity through it, The 5 volts supplied by another source will back feed through that limiter to ground. So that limiter is wicking away some portion of the 5 volts, as if it were a 4th gauge.
No one even needed to open a gauge to disable a limiter. Simply lift the gauge from the housing and cover the small piece of metal on its backside with electric tape to isolate it from ground. Take the blue with white tracer out of the round connector and route it to any substitute regulator mounted anywhere you like. It doesn't have to be on the back of the inst' panel.
The unit from Real Time Engineering is the one to buy. It costs more but... it includes ground fault protection. That little 7805 chip does not. If it looses chassis ground, 12 volts goes straight through it and out on the wire that should be only 5 volts. That will fry all 3 of your gauges. The RTE unit has LED indictors on it so may as well mount it where they can be seen. Nowhere to mount it on the back of the rally panel anyway.
A guy named Rick Erinburgh (or something like that) first published this "open the gauge" procedure to a Imperial website about 20 years ago. He hadn't look at it close enough. Then others propagated that info without doing their own study.
In the end, I hope you find only something simple,, a loose pin at the blue with white, or the fuel gauge is a little loose at its mounting nuts, limiter lost its ground, you didn't need any of this info.
If you do determine a substitute regulator is needed and you'll convert the amp gauge to a volts gauge... the blue with white should also feed switched 12 volts to the positive side of the volt gauge. You will need to add a ground wire to negative side of a volts gauge. There is a proper method to do that too.

Somewhat of an update: So I still haven’t had a chance to do any meaningful troubleshooting. I verified all ground connections and removed the +12V supply to the tach from the blue wire with white trace. You’ll remember I mentioned in the original post that this is where the old tach’s backlight feed was tapped, and I used it to feed power to the new tach, which may have been a mistake.

Fuel, temp and oil gauges are working at the moment, but the fuel needle is still tending to ‘wander’. Tach is the same (visibly getting power, now from the fuse box, but not responding to the tach signal).

I suspect my issue may have originated with the faulty tach. I’m a little unsure about how the tach being fed from the blue/white wire may or may not have affected the voltage limiter inside the fuel gauge. You said the blue/white feeds the limiter, but the schematic in my ‘67 service manual shows it going to the brake warning light.

Again, no real troubleshooting accomplished. The stuff I mentioned in the prior paragraph is based on gut feeling. Any thoughts?

 

[Mattax]

As far as the wires go, all I can say is that on my '67 notchback there is seperate blue with white trace power feed from the run switch to the instrument connector.
That's my cheat sheet above, even though its based on the pdf created by @1969383S which in turn he based on the factory diagrams.
I'm pretty sure I have the positions correct on there for my car, but lets check because I could have marked up the paper copy when working at the shop.

FWIW the harness on my '67 is 2857 252

One of the other numbers might be a date code.

Here is the headlight switch connector. There's two blue with white wires at the I-1 terminal.
The thinner one, probably 18 ga., goes to the instrument panel connector.

I suppose the brake warning feed and the gage feeds could be switched, but the factory drawings agree with what I have. That doesn't mean thats the way they were built, or always built. Just what I found on my car in this case matches the drawings.

("C" Series = 1967 Models)

 

[Mattax]

You’ll remember I mentioned in the original post that this is where the old tach’s backlight feed was tapped, and I used it to feed power to the new tach, which may have been a mistake.

It should have worked as long as the connection was good.

Fuel, temp and oil gauges are working at the moment, but the fuel needle is still tending to ‘wander’. Tach is the same (visibly getting power, now from the fuse box, but not responding to the tach signal).

Maybe Redfish has an idea about the wandering fuel gage.
I know its a PIA, but if you wanted to rig a 22 ohm resistor to the fuel sender connector, connect the other end of the resistor to the ground strap (fuel line), the gage should read about 1/2 steady when the car is running.

Tach is the same (visibly getting power, now from the fuse box, but not responding to the tach signal).

How does the tach visibly get power but not respond to the signal?

Also was the aftermarket tach working directly off the coil negative or some other arrangement?

 

[67fish383S]

How does the tach visibly get power but not respond to the signal?

Also was the aftermarket tach working directly off the coil negative or some other arrangement?

I can tell the tach is getting power because when it is unpowered, the needle rests below zero. When it powers up, the needle moves to zero. It just no longer reads above zero when the engine revs, so I am assuming it is defective. And yes, it is being fed the tach signal from coil negative. I need to verify with another device that the signal is still reaching the tach before I pull the tach and try to return it.

Incidentally, I drove the car to work today (~25 miles) and (knock wood) all gauge operation (other than the tach) appears to have returned to normal. The fuel needle is stable again. It is really starting to look like the failing/failed tach was interfering with the other gauges somehow. When I install a replacement tach, I will keep the power feed off that blue/white wire just in case.

 

[RedFish]

I would think a tachs backlight would be connected to the orange wire/illumination circuit somewhere. Tach is accessory. These harnesses didn't include provisions for accessories. Thats why the factory tach package included a add on harness for it. I dont know how you or a previous owner are going about tapping wires or how you lost power to the limiter. Twist them together and tape them up doesn't always work. Could be a loose pin at circuit board too. Moving the wires about would move that pin. The only wires that depend on the pins are those to light bulbs. Every other wire could be attached directly on the corresponding post with a ring terminal, same as the wires on the amp gauge. Toothed washer and 10-32 hex nut on top of the speedy/PAL nut. E-body for example doesn't have a printed circuit board. all the wires are attached with 90 degree push on like the one on your noise cap'. Those owners have to know which color wire goes where.

 

[67fish383S]

I would think a tachs backlight would be connected to the orange wire/illumination circuit somewhere. Tach is accessory. These harnesses didn't include provisions for accessories. Thats why the factory tach package included a add on harness for it. I dont know how you or a previous owner are going about tapping wires or how you lost power to the limiter. Twist them together and tape them up doesn't always work. Could be a loose pin at circuit board too. Moving the wires about would move that pin. The only wires that depend on the pins are those to light bulbs. Every other wire could be attached directly on the corresponding post with a ring terminal, same as the wires on the amp gauge. Toothed washer and 10-32 hex nut on top of the speedy/PAL nut. E-body for example doesn't have a printed circuit board. all the wires are attached with 90 degree push on like the one on your noise cap'. Those owners have to know which color wire goes where.

Yes I checked for proper seating of all the pins and connectors. The previous owner had stripped a section of the insulation from the blue/white wire and twisted/taped the backlight feed to the old tach on to it. I simply soldered and shrink wrapped the same connection (but instead feeding +12V to the new tach, there is no separate backlight) when I installed the aftermarket tach. While there is no concrete evidence to back up my theory at this point (only circumstantial), it would appear that the faulty tach was disturbing the operation of the IVR inside the fuel gauge and causing all of the gauges in the cluster to behave erratically. The assumed path of the disturbance is the blue/white wire. Since removing the power feed to the faulty tach, gauge function appears to have returned to normal. I am taking no bets that the problem will not re-occur however. They could have been co-incidental events (the tach failure and the flaky gauges) caused by disturbing the 53 year old cluster in the first place to do the tach installation. I am planning to pull the cluster again to remove/return/replace the tach and overhaul the cluster with new PCBs, lamp sockets, and perhaps replacement gauges, although those are pricey and currently out-of-stock.

 

[67fish383S]

Thank you to everyone who took the time to contribute all of this valuable info. It is much appreciated!

 

[cgfen]

interesting, value packed thread.
thank you

 

[67fish383S]

Unfortunately you need to dissassemble the face from the fuel gage and disable the built in IVR while leaving the part of the gage that works the fuel level needle alone. I used a small pair of miniature wire snippers to carefully unroll the edges and slide the face off. Mark the back of the gage face and gage housing in one spot so you can re crimp it back together in the same place on reassembly.

Your new IVR will mount on the exterior of the back of the instrument cluster. Why chrysler elected to mount it inside the gas gage on this type of gage panel is beyond me. The first pic says to remove the small black insulated wire, but also clip off and remove the bimetal point contactor that has the bare wire coil wrapped around it. Leave the 3 studs on the back of the gage as one is your tie in for the 12V feed, and the other is your 6V output, along with a ground. The remaining 3rd stud coming out of the gage not mentioned in my diagram is your sense wire that goes to the fuel sending unit. I also ended up threading in a stainless steel stud in the location shown as a dedicated ground.

The solid state chip you need is an NTE960 along with a small capacitor and will require come basic solder skills. See schematic and pix below. The NTE960 will take up to 35VDC input and drop it to 5.5VDC output. So running 12-13VDC through it is asking really nothing of it in the grand scheme of things. My wire color coding is red for 12V input, yellow for 6V output, black for ground. I was making these for awhile and selling them but this is a nice DIY weekend project.

(Note in the schematic it shows 2 grounds. The wired ground to the cluster, but also the chips mounting tab. The mounting tab is the second ground and must be grounded for the chip to work)

View attachment 1715598679

View attachment 1715598680

View attachment 1715598681

I just did this modification on a gauge set out of a parts car that started smoking the first time I tried to test them. Luckily I caught it before the gauges burned up. A bad original IVR was the only thing that made sense. I ended up using a LM7805BT chip to build the replacement because that's what I had on hand. It's all working great now. Just wanted to say thanks again for the instructions.