Wiring 'factory' gauges 'directly'???

[7900_Blazer]

My truck is a 1975 Blazer - pretty much a basket case when I bought it as a project with my 15 year old.

Each individual gauge in the dash cluster has threaded 'posts', so my question is can I wire them directly to their various sensors?

For example:

1. can I connect the fuel sending unit wire (tan wire I believe) directly to one post of the fuel gauge and 12 volt power to the other post and it work?

2. can I connect the temp gauge sensor wire directly to the temp gauge and 12 volt power to the other post and it work?

I've already put in a mechanical oil pressure gauge and a tach (which wires directly to the distributor and 12 volt power).

Anyone done this using 'factory' (LMC truck) gauges?

Thanks for any direction.

 

[Keith Seymore]

I have an '87 IROC-Z tach installed in my '74 Chevelle cluster, and have it hard wired (because the printed circuit would no longer be compatible).

So - yes, in that case.

K

 

[Snoots]

Yes and yes.

 

[7900_Blazer]

So any detailed direction on doing this?

I'm assuming I could do the following:

1. run a 'shared' ACC 'hot' up to behind the gauge cluster
2. run a 'shared' ground up to behind the cluster
3. using a schematic - find which pin in the gauge cluster plug that is the wire for each (fuel sending, temp sensor)
4. solder in some connectors and wire each gauge to the shared ACC 'hot', the shared ground and to the specific wire for that gauge.

Does that sound about right?

 

[Juggernaut]

So any detailed direction on doing this?

I'm assuming I could do the following:

1. run a 'shared' ACC 'hot' up to behind the gauge cluster
2. run a 'shared' ground up to behind the cluster
3. using a schematic - find which pin in the gauge cluster plug that is the wire for each (fuel sending, temp sensor)
4. solder in some connectors and wire each gauge to the shared ACC 'hot', the shared ground and to the specific wire for that gauge.

Does that sound about right?

Yes, you are on the right track. I did this very same thing back in the early 90's when my printed circuit board shorted out. I had purchased a Sun gauge pack with a wet oil pressure and water temp gauges. I didn't want working gauges mounted externally somewhere in the cab and dead gauges in the dash, so I cut out the back of the plastic housing, removed the circuit board, mounted the new gauges in place of the non working gauges, then spliced each wire from the gauge or light back to the wires from the circuit board connector. My factory volt meter worked fine doing this, just follow the circuit path back to the connector and splice into the wire it matches up to. Now, for what I did WRONG. Do NOT use wire nuts. It's tempting to connect all the grounds, or all the lighting wiring using wire nuts, but don't do it. Also, there is a right and a wrong way to crimp a connector on a wire. Look at the end of the connector where the wire goes in and you will see a split in the metal. When you crimp the connector on, the dimple needs to go on the opposite side of the split. Both of these left me with gauges not working while I was driving.

 

[7900_Blazer]

Is there anyone that has the experience and can tell me explicitly how to BENCH TEST a stock GM temp gauge an temp sensor?

I have not been able to find a single diagram showing how to do this.

specifically I need to know the following:

1. which gauge post is 12+
2. Which gauge post is for temp sender sending wire
3. Which gauge post is for ground
4. Is the sending unit grounded?

any video or specific info on BENCH TESTING a temp sensor and gauge would be very much appreciated!!!!

 

[AuroraGirl]

Is there anyone that has the experience and can tell me explicitly how to BENCH TEST a stock GM temp gauge an temp sensor?

I have not been able to find a single diagram showing how to do this.

specifically I need to know the following:

1. which gauge post is 12+
2. Which gauge post is for temp sender sending wire
3. Which gauge post is for ground
4. Is the sending unit grounded?

any video or specific info on BENCH TESTING a temp sensor and gauge would be very much appreciated!!!!

What year

I’m asking because the year is kinda the important part…
Single wire nub or blade, multi wire,etc.., the sender range, the gauge range..

 

[7900_Blazer]

I figured it out… the gauge was bad…

 

[AuroraGirl]

I figured it out… the gauge was bad…

That happens
My favorite test is apply energy, gauge goes one way

remove energy, it should go the other

I played with a 77 Ford Ltd fuel gsuge like this, it was funny how it would inconsistently slowly drop to e but make weird pauses on the way

 

[7900_Blazer]

Actually I didn’t get it to work.

it’s a ‘75 Blazer; direct wired as described below.

Bench testing it.
- Drivers side post connected to temp sensor
- Opposite side post to 12 volts
- Bottom post connected to ground
- Second ground connected to the temp sensor itself (to simulate grounding to the block).

Took a lighter and heated the sensor, it increased to gauge temp as expected.

Once I put it in the gauge cluster though in the truck, when you screw it into the joint mounting post, gauge seems to short out against the fuel gauge next to it and jumps to 220 or so.

Disconnect it from that mounting post, gauge sets at about 120 or so and never moves.

Not sure why it is shorting out when touching the fuel gauge???

Any thoughts?

 

[AuroraGirl]

Actually I didn’t get it to work.

it’s a ‘75 Blazer; direct wired as described below.

Bench testing it.
- Drivers side post connected to temp sensor
- Opposite side post to 12 volts
- Bottom post connected to ground
- Second ground connected to the temp sensor itself (to simulate grounding to the block).

Took a lighter and heated the sensor, it increased to gauge temp as expected.

Once I put it in the gauge cluster though in the truck, when you screw it into the joint mounting post, gauge seems to short out against the fuel gauge next to it and jumps to 220 or so.

Disconnect it from that mounting post, gauge sets at about 120 or so and never moves.

Not sure why it is shorting out when touching the fuel gauge???

Any thoughts?

It touches the fuel gauge..?are you using a custom holder.. or you mean the printed circuit? If you touch the metal bodies I’m thinking one has some failing internals and doing some weird stuff

wait

which fuel gauge, smal ome?

 

[7900_Blazer]

It touches the fuel gauge..?

wait

which fuel gauge, smal ome?

yes, fuel gauge and temp gauge are next to each other. The gauges share a mounting post /screw that holds them into the plastic gauge cluster.

 

[AuroraGirl]

yes, fuel gauge and temp gauge are next to each other. The gauges share a mounting post /screw that holds them into the plastic gauge cluster.

Isolate with a small non conductive thing but it sounds like maybe a cluster grounding issue or a dying gauge

 

[Dan Brown]

I'm restoring a 1974 K10 and built my own gauge panel out of Aluminum sheet and put Autometer gauges in it. My 74 originally had printed circuits, which I'd bet your 75 did, too. I don't recall if the original gauges had the capability of being wired directly. The oil pressure gauge was mechanical. You can buy pre-made gauge panels, but they are expensive. Attached is a picture of my panel.

You must be registered for see images attach

gauge panels for your Blazer, but they are expensive.

 

[dsteelejr]

@7900_Blazer

I have to ask, why do you want to do this in the first place? I have some experience with factory gauges and rewiring and whatnot and it seems like a pain in the butt. Also, it would make it more difficult to pull the cluster out in the future having each gauge wired directly rather than using the facorty connector.