One more speedometer question

Topic: One more speedometer question (Read 1720 times) previous topic - next topic

One more speedometer question

May 20, 2010, 04:46:54 PM

Ok, with any luck, the T-Bird will be getting registered next week! But the speedometer still isn't working. This is an 84 digital cluster.

The speedometer reads 0 at every speed, I figured it was the speedometer cable, but it isn't. I verified that the cable is not broken, and the cable does spin while the wheels turn. The...bearing? that the end of the cable plugs into spins fine as well, and when the cable is plugged in, the bearing also spins. But even while the bearing spins, it reads 0 mph, even if I spin the bearing by hand.

So, it's most likely an electrical problem, no? All of my fuses appear to be good, is it possible for those relay boxes to fail?

Thanks

One more speedometer question

Reply #1 – May 21, 2010, 11:24:59 AM

No ideas?

One more speedometer question

Reply #2 – May 22, 2010, 03:49:55 PM

I know that these clusters were kinda uncommon, and most of you guys have 85-88s, but does anyone have the pin-out for the cluster? I'm gonna try to take it out and bench test it. I'm really not sure why it's doing this, but hopefully I can try to eliminate the cluster itself as a problem if I can see it working outside of the car.

One more speedometer question

Reply #3 – May 23, 2010, 08:49:29 AM

You might be looking for this or this.

One more speedometer question

Reply #4 – May 23, 2010, 10:57:25 AM

Unfortunately, no. That is the type of information I need, but not for those clusters. The 83-84 digital clusters were different. They used only one 18 pin plug and a traditional speedometer cable.

One more speedometer question

Reply #5 – May 23, 2010, 11:47:25 PM

Quote from: dragon574444;322946

Unfortunately, no. That is the type of information I need, but not for those clusters. The 83-84 digital clusters were different. They used only one 18 pin plug and a traditional speedometer cable.

Dude I have a digital cluster for a 1980-82 Tbird and the guts are the same. That is the digital readout for speed and fuel and the odometer setup. The guts were carried over for use in the 83-84 cars with modifications only to the cluster face, cluster housing, turn signal indicators and idiot lights.

If you find that you have faulty electronics I have guts that are working properly and I have my cluster for sale if you happen to need it. The parts will unfasten and install directly into your cluster unit.

This cluster does not use the external speed sensor on the tranny. It is cable driven for sure and the speed sensor is made into the back of the odometer assembly. The cable drives the speed sensor there.

Looking at the back of the cluster the speedo readout unit is attached to the cluster housing with four studs that have copper nuts that make the connection to the printed circuit. Looking left to right from the back of the cluster the connections are as follows:

1: Dash Light Illumination (Dims the readout when lamps are turned on)
2: Ground
3: Speed signal out to tripminder if equipped
4: Ignition on

From these studs you can trace the circuit to the pins on the connector.

Now when I had my cluster installed, I was reading zero at one point because my speedo cable was not fastened into the back of the odometer unit correctly. You can always tell if the cable is installed correctly if you drive it and the odometer numbers turn. If the odometer turns then the problem is within the cluster itself. The speed sensor on the back of the odometer mechanism may be failing to generate a signal. Take the cluster apart and check the internal wires from the speed sensor to the digital speedo readout unit and see if any wire connections came loose. You can also attach a multi-meter to the connections from the speed sensor and spin the back of the cable connection with the cable removed and see if you get a pulsed signal with each rotation. If you get a pulsed signal then it could be faulty electronics on the digital speedo readout not being able to process the signal.

I hope this helps!

One more speedometer question

Reply #6 – May 24, 2010, 12:00:03 AM

Quote from: Trinom;322942

You might be looking for this or this.

Unfortunately the wiring for 85-88 clusters do not apply to 84 and earlier ones. Some but not all of the wire colors are indeed the same. Also, the 80-84 clusters use a single gray connector instead of two.

One more speedometer question

Reply #7 – May 24, 2010, 04:45:33 PM

Thanks for the help Watchdevil. There's a few things though...I see 5 main terminals with nuts on them.

Does that seem right? I don't want to blow it up by putting 12 volts where I shouldn't.

Also, the odometer does change while the cable is hooked up, so it must be the cluster itself, right?

This is where the cable plugs into. It spins that bearing.

Now this is most likely the problem, this...thing? It looks kinda like a voltage regulator, but it could be anything. Attached to the bearing the the speedometer cable plugs into is a platter of some sort that spins at the same speed as the cable. The platter has holes in it at regular intervals. The platter goes in between that black box, and the wires attached to that go to the main circuit board. I kinda would expect to see maybe two brushes coming off that black box, as that would make a pulse when the platter spins between the two brushes, but I don't see anything like that. Could it use light? My mind is boggled. The odometer is a purely mechanical, isolated system that is also runs off of the cable, but has nothing to do with that platter.

I can't see any major signs of malfunction, no shorts, no giant burn marks on the board, no broken wires, no cold solder joints...

Don't throw that cluster away

One more speedometer question

Reply #8 – May 24, 2010, 04:59:00 PM

Here's some better pics of the "black box" and the platter

Like I said, there's nothing between it...I have no idea how it works...magnetism maybe? But magnets don't just go bad, and that's what I had put my bets on for the part that failed.