FJ45 Dash Panel Ammeter Wires (1 Viewer)

[knuckle47]

Did a search and found a few thoughts on this topic but I am still a bit confused. Wiring does this to me lately

the original dash panel has been replaced but the ammeter is not doing anything so opening it up reveals the wiring shorted together and I assume, as a bypass. Battery charges at 14.1+ and I am hoping to re-connect this properly with doing some really stupid stuff. It seems fairly straight forward until I look in the MANUALS. I remember my fusible link in 1974 was near the coil up by the battery. I see nothing in the engine bay and am more than aware of PO modifications and the screwups they create.

what I don’t understand is how to reverse engineer this for safety

Also, the new dash panel has a 3 prong plug just above the ammeter lugs with very tight spacing …anyone know what these are used for?

 

[1MAC]

First you need to determine whether or not it is safe to connect those back to your ammeter. What alternator do you have in the vehicle?

 

[knuckle47]

Replaced the dead replacement with a 45 Amp AC Delco …. Three pronged plug fit the alternator easily Same one I had used in the FJ40 a few yrs. Back. That had a working ammeter and fusible link and it charged perfectly. Since they appear just twisted together…it seems like I could just place an ammeter in line…but then, I have been in situations like this where it seems ok but it wasn’t

delco part #334-1551

GM part #1913454

external voltage regulator

 

[charliemeyer007]

For like $9 you can buy a 60 amp meter to scab into the system and see if it works without risking your dash meters. You can even fuse it for a few more bucks.
Amazon product ASIN B08MT93Y9L

 

[pjohnson]

What does the front of your gauge panel look like?

 

[knuckle47]

What does the front of your gauge panel look like?

Basically an FJ40 instrument cluster but the gauge is a 50 A instead of a 30A

 

[pjohnson]

Basically an FJ40 instrument cluster but the gauge is a 50 A instead of a 30A

It's probably Kph instead of Mph also?

That gauge cluster is not a direct swap. The ammeter requires a shunt(?) To function properly. If you hook it up directly as per your old gauge, it will kill it.
There's a couple of threads about retrofitting these gauge clusters.

Also, the OEM wire color for the ammeter is white/blue stripe, not red.

 

[knuckle47]

@pjohnson. So the crazy part for me…I read guides, manuals and schematics to locate this wire but some PO has changed the color code. I am so accustomed to this from my vintage motorcycle days where a 70 year old motorcycle had u deer gone a major change every q0 years of another owners view. Problem is that the wiring on the truck in 15 times for complex.

I will start to look for these conversions….thank you for the help

 

[45Dougal]

It looks like the two red wires are replacements for the original ammeter wires.

They should measure 12V.

They carry all power to your truck, so if you disconnect them from each other, I expect your truck will have no power?

In this case, one will read 12V and the other not. The first one is the +ve side of the ammeter.

The problem is that your new "Amp meter" is actually a voltmeter in sheep's clothing, so it needs an external shunt in order to operate correctly.

You need to add a shunt across the pins of the ammeter before connecting it up, otherwise it will blow (if the PO didn't already blow it when it was first installed).

Better option is to open the cluster and replace the ammeter with the old 30A one. Then fit the cables as previously.

 

[knuckle47]

It looks like the two red wires are replacements for the original ammeter wires.

They should measure 12V.

They carry all power to your truck, so if you disconnect them from each other, I expect your truck will have no power?

In this case, one will read 12V and the other not. The first one is the +ve side of the ammeter.

The problem is that your new "Amp meter" is actually a voltmeter in sheep's clothing, so it needs an external shunt in order to operate correctly.

You need to add a shunt across the pins of the ammeter before connecting it up, otherwise it will blow (if the PO didn't already blow it when it was first installed).

Better option is to open the cluster and replace the ammeter with the old 30A one. Then fit the cables as previously.

Brilliant….. looks like I can fix it that way…. THANK YOU…THANK YOU

 

[knuckle47]

It appears the ammeter is independent of the cluster… does that seem true? Possibly a ground it all that’s common Thru the mounting and case?

 

[knuckle47]

Does someone know what the newer 3 pin spade lugs on the back of the new cluster does?

 

[45Dougal]

The ammeter is independent and doesn't need a ground.
The three pin connector is linked to the new style ammeter (only needs small gauge wire due to being a volt meter). Also maybe included a ground for something else on the panel??

 

[1MAC]

Make sure your ammeter is a 50A, not a 30A. A 45A alternator makes enough current to burn up a 30A gauge.

 

[knuckle47]

@45Dougal THANK YOU great suggestion as that actually works. I took the old ammeter out of the old cluster. It seems that the old cluster was replaced as the needle was broken off of the gas gauge. The are several differences between the two. The easy one…the old gauge is dirty and not the brilliant white of the new one. A q-tip and some soft scrub cleanser did a reasonable job of brightening it up. The spacing of the posts are wider on the old 30A gauge so I drilled out the mounting holes to fit the posts in and provide some isolation from the speedometer cluster chassis.

I reassembled it using heat shrink tubes over the post to be 99.9% sure they would not short out as well and added the old fiber washers from the old case. Ohm meter confirmed the isolation so tapped the tabs down, installed the cluster and battery. The key on position dropped the needle about 35% to negative and starting the engine brought it up to about 50% positive.

So, this problem is solved. Next need to figure out why the speedometer doesn’t work… it think this one is in the trans.
The photo lighting is poor in the finished cluster but it is in and working ordered a few drops of fluorescent red paint for the actual restore process

 

[45Dougal]

Great to hear you've had success
Always good to see pictures too - they're so helpful to the next man searching for help.

 

[knuckle47]

@45Dougal your suggestion was IDEAL for me. Would be nice if it was a direct fit but as long as you maintain complete electrical isolation…perfect. I would love to eliminate the circuit board in this area and make the attachment as toyota did with their older gauge panel but I am not yet sure that there are no continuity issues by doing that. I’ll update as I think about this some more. Gotta dig out the ohmmeter again and begin checking

 

[B y r o n]

See post #21 in this thread for the connector.

 

[knuckle47]

@B y r o n perfect…. I am learning this hour by hour. Took a few more pictures…it’s a rainy day here.

By drilling out the smaller gap for the older 30A gauge, it is possible you may destroy the loop on The circuit board feeding some of the lamps in the cluster. The green trace feeds the 50A gauge thru the 3 spade lugs and the harness shown in @B y r o n link.( thanks..good find)

toyota insures a positive isolation using the insulators with a small ridge to keep them in position ( see pencil)

the hole most affected by drilling a closer binding post location is in yellow

‘’hey, maybe your in the same boat. i was looking for how to shunt the 50A gauge but never found it

 

[45Dougal]

I would use ring tags to connect directly to the ammeter studs, and ignore the tracks - they're not connected to anything else.
The 3 pin connector and the tracks on the board are not rated for 30A so might burn out after a while if you use the connector with the old ammeter.

The whole current actually flows through the 30A ammeter, whereas the later 50A ammeter uses a remote shunt, so the current goes through the shunt rather than the meter (which is a much better way of doing it really, hence the change). The meter just measures the small voltage across the shunt - the current through the connector is therefore very small.