Hello once again all! I don't know if anyone's ever tried this before, but if not, this may make a swap from an idiot light cluster to a gauge cluster much easier if you don't want to go to the trouble of replacing sensors and harnesses (assuming you don't have a show truck and don't mind having two dead gauges). My method is simple and relatively painless, yet effective. Since I hard-wired the cluster, I had the freedom to rearrange my indicator lights. I popped the two lenses furthest to the right out of my bezel, replaced them with red tape and simply wrote "oil" and "alternator" in the spaces, then ran the wires from the oil and amp lights to the new spaces.

This, of course, was my main reason for swapping clusters, for the factory tach. Here is a pic of everything installed and put together:



Here you can see how I have rearranged my turn indicators and added the oil and alternator lights:



And finally, a close-up of the oil and alternator lights:



Hope this helps anyone else wanting to make the swap, have a good day everyone!

 

Looks good, did you paint the gauge faces? they look silver in the pic I saw.

For the oil you just had to put the pressure sender from the parts truck in and it would have worked. The Amp gauge I think *should* have worked as well but I can't remember for sure. I did it on an '84 that a buddy swapped a 400 into but its been about 7 years now.

 

Ammeter requires a shunt in order to work. If you wired it straight up to 12V without one, it'd fry in no time, since it's got super-thin strands of wire inside it that can't handle all that power. The shunt drops it down to where it works properly and gives you a reading without turning those wire strands red-hot and burning stuff up. I know that there is a little bar piece on the idiot light clusters down by the charge gauge that has something to do with its functioning, though I can't recall what it does. I think it allows the light to come on when it's supposed to...

Whether or not that ammeter will work if/when you install a shunt and wire it up properly is anyone's guess, since alot of times even factory-installed ammeters in gauge-equipped trucks don't work after 30 years. I just got lucky with mine when I did my tach cluster swap (truck had all gauges except tach originally), my factory one didn't even work.

Alternatively, you could look at putting the oil and charge lights into your tach cluster and wiring it up that way for a factory look. Just an idea.

BTW, when I first read here about having two dead gauges, I was like, "man, that would annoy the mess out of me"....but then I remembered that my oil and temp gauges are dead on my truck anyway, since I pulled their sending units in order to run a couple of Autometers in their place. So it ain't as bad as I thought lol.

 

You do realise you removed a 500 ohm impedance resistor from the altenator warning light. And that impedance resistor is a part of the warning light instrument cluster right? You realise if you didn't make alowance for that resistor in your wiring, and the altenator warning bulb burns out that you will lose your charging system right?


The only proper way to put full gauges into a truck that only came with warning lamps, is to swap out the whole main underdash harness and to swap out the altenator harness for a truck with gauges. There are at least 13 different circut pathways between one and the other. This is why Ford made the plug connections for the clusters so different; so the required parts would be swapped in order to make this swap safe.

If you are not a wiring expert, doing it in any other way invites problems, (like the one I mentioned in my first paragraph) especially if you have no experience with wiring. Doing one error on a swap like this could cause a pretty serious fire. IE: 60 Amps from the altenator going through an ammeter that is only rated for 5 amps. At least you didn't hook up the ammeter without a shunt directly in circut between the altenator and battery. That would literally melt the ammeter in the cluster under certain charging conditions.

If you want to do this properly, and have everything work, without added danger of fire, find a main underdash harness, and an altenator harness for gauges, and swap them out. It's not that hard and would take me less than 3 hours to do if the main harness is in good shape. The hardest part is to find the year correct harnesses.

These are the years that are the most compatible:

Main Harness: Try to get the same year harness
1980 (You can swap a 1981-1982 harness if you change the headlamp switch and instrument cluster to match the year)
1981-1982
1983 (You can use a 1981-1982 or a 1984-1986 but be warned some of the plugs will not match up: IE: Clock and headlamp warning and seat belt buzzer etc depending on year and some of the holes in the firewall will not match for 1984-1986)
1984-1986

The altenator harness should match the same amperage of the altenator you have. This will be shown as a 16 gauge for 40 and 60 amp altenators, and 14 gauge for 70 and 90 amp versions. There is also differences between external and internal regulated harnesses, which should be pretty straight forward.

 

Thanks. Yes, I painted them a metallic silver and painted over the characters with a black paint marker. I just wanted to quickly rig this up so I could finally have my tach, they're a major rarity around here. I'm not going to worry too much about the senders and all until I actually get the year correct harness and do it right (cluster came from an '85, and my truck is an '80), so I'm waiting to see if a 1980 harness comes along.

I wish Ford had designed their clusters that way, doesn't really make sense why they didn't to me. If the idiot-lighted clusters had a recess for the tach, I would have been just as happy doing it that way. Unfortunately, there's no way to install the idiot lights into the new cluster...

Yes, I am aware that's how it worked ORIGINALLY. However, after my alternator finally gave out and I didn't have the money for a new one, I borrowed the GM style alternator off of my Jeep Wagoneer to see if it worked, which required a few alterations to the factory wiring under the hood. With this alternator in place, I have actually tested my charging system with the entire cluster out (no bulb, resistor, or anything to complete the circuit in the cluster) and my charging system still functions normally. Surprisingly, the idiot light still works perfectly normal as well. I do intend to do it the safe way with the new harness as money and availability come into play, but until then, I'm pretty sure everything will be fine as-is.

 

Just to clarify: I did think about the resistor in the cluster as I did this swap, until I figured out my altered charging system still functioned as normal. What I was going to do was mount the resistor in an out-of-the-way place on the cluster and wire it in, thereby making this possible for anyone still using an absolutely stock charging system.

 

My point with this is, make sure it still works with the bulb removed.

If everything was original, removing the resistor put the alternator ignition circuit, and the warning lamp in series. This would cause the alternator to stop charging if the warning bulb blew out. One of the reasons why the bypass impedance resistor is in the circuit, to wire it parallel.
The Parallel Circuit

 

double post

 

I have tried with bulb removed, and everything still functions as it should. I don't recall off hand exactly what I did to install the Delco alternator, but it no longer relies on the bulb/resistor/cluster circuit to charge anymore. If I were to hook the original style alternator back up with the factory wiring, then I would indeed have to put the resistor back in the warning lamp circuit. I believe it was something to do with how the old alternator ran through the voltage regulator on the fender, and this one has an internal regulator so it had to be ran straight to the battery.

 

That would make a difference yes. Since I do not know how you wired in your GM alt, I could not comment.

On Ford systems of this vintage, the alternator and voltage regulator has to have a field signal, as well as the ignition switch on, to charge. Not only does the wire in question operate the warning light, it tells the components that the ignition is on. On ammeter equipped trucks the green/red wire is hooked directly to the ignition switch, and the wire is hooked up to the stator position of the regulator. This is why the stator is only used for the choke on ammeter systems, and only three of the four spaces on the regulator are used. On warning light systems all four spaces are used on the regulator, and the stator signal from the ammeter goes to the regulator as well as the choke.

 

Basically what I have done is created a one-wire setup. The field wire and the positive output both go to the battery. As with all one-wire setups, I have to rev the engine slightly on start-up for the alternator to begin charging. Since this alternator is internally regulated, and the factory regulator on the fender is still in place, my alternator warning lamp still works and doesn't require the resistor. However, as I said earlier, to change back to the Ford style externally regulated alternator, I would have to wire the resistor back in parallel with the bulb.

 

FYI,

My '87 had a resistor soldered right across the bulb holder for the alternator warning light.
The '89 replacement cluster had it soldered to the flex circuit.
I'm sure you could find a bulb holder with the resistor and just use it in the that socket.

 

An FYI, when Oldsmobile introduced their diesel, they actually have two charge idiot lights in parallel, one in the cluster, the other in a blind capped holder taped to the harness.