Diagram for 12V Input wires going to the factory gauge cluster connectors?

JCBeaver

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Hello everyone,

I have a 1993 Mustang GT and I am experiencing reduced voltage out of the red/yellow stripe wires 12V Input wires going to both of the gauge cluster connectors.

I am trying to pin point where the 12V source comes from for those wires so I can try to see what is causing the voltage to reduce along the path. I should be seeing 12V but I am seeing steady 4V instead.

The reason I am asking is because I am using this wire as my accessory wire to power up my aftermarket Dakota Digital gauge cluster. It worked perfect other day before I removed it to do a few things and then bam it quit supplying 12V again. I cant quite figure out why yet.

See attached picture which shows the gauge cluster connectors' pins. The Pins I am referring to are #4 and #7 on the left connector. The wire also can be found on pin#7 on the right connector. Does anyone have the diagram for those wires on where they start and end? Thanks in advance!
 

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JCBeaver

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Hello guys,

Today I learned that my VPWR wire going to my factory coolant sensor connector also is showing only 4V. Similar to how my ACC wire is showing.

Learned the hard way because my car overheated and I noticed that the fan never turned on. Due to the low voltage from the VPWR coolant sensor wire.

I suspect that there is a gremlin somewhere on the VPWR circuit however when I measured the VPWR wire at the ignition coil and the MaF connector. Both shows 12V.

I am genuinely confused haha. Any suggestions?

Thanks in advance!
 

JCBeaver

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I also tested every other 12V key on points such as purge canister, maf, AC cut off, egr and everything is showing 12V except for the coolant level sensor wire near the radiator.

Can anyone tell me how can one wire not register 12V while all other wires from the same circuit are registering 12V? Forgive my ignorance. I am still learning how exactly all this works.

Thanks again
 

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JCBeaver

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Sorry for yet another post. I wanted to note that I noticed the coolant sensor wire actually shares the very same wire color - red/yellow stripe which I am experiencing reduced voltage inside the car at the gauge cluster.

While all other outputs I measured had their own wires. They are all NOT red/yellow stripe wires however they do come from VPWR source if I am making any sense.

Thanks
 

jrichker

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I also tested every other 12V key on points such as purge canister, maf, AC cut off, egr and everything is showing 12V except for the coolant level sensor wire near the radiator.

Can anyone tell me how can one wire not register 12V while all other wires from the same circuit are registering 12V? Forgive my ignorance. I am still learning how exactly all this works.

Thanks again
It could be a broken wire or bad connection. Use your multimeter or DVM to check the resistance between the coolant sensor power wire and one of the other wires on the same circuit. It should b 1.5 Ohms or less.
 

JCBeaver

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It could be a broken wire or bad connection. Use your multimeter or DVM to check the resistance between the coolant sensor power wire and one of the other wires on the same circuit. It should b 1.5 Ohms or less.
Which ohm setting on dMM should I be reading?

The red and yellow wire is no longer registering any voltage. It was showing 4 volts earlier and now I am showing zero at both coolant sensor and cluster plugs.

I dialed into 200k ohm setting and it was reading around 150.X ohm. What does that mean? Once again there is no voltage. Guess this wire is dead now?

Thanks
 

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jrichker

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Which ohm setting on dMM should I be reading?

The red and yellow wire is no longer registering any voltage. It was showing 4 volts earlier and now I am showing zero at both coolant sensor and cluster plugs.

I dialed into 200k ohm setting and it was reading around 150.X ohm. What does that mean? Once again there is no voltage. Guess this wire is dead now?

Thanks
Use the 200 ohm range.

Automotive circuits are mostly simple stuff: a power source, a connection path, a control device, a load, and a ground.
The battery/alternator is the positive power source.
The wire and fuses are the connection path.
Control devices are switches, relays and sensors.
A load is a light, motor, solenoid, relay coil or heater element.
In automotive circuits, grounds are the return path so the electrical power can flow from the load to the negative side of the power source.
Electricity flows like water:
Voltage is like pressure,
Current in amps is like volume,
Resistance is like the kink you put in a garden hose to decrease the pressure or volume.
Power is pressure multiplied by volume or voltage multiplied by current (amps)

Digest that, and you just got the first 3 days of Electricity 101.

Use some jumper wires (connection path and ground) to hook up a switch (control device), a battery (power source), a light bulb (load). Now make the light turn on and off with the switch.

That's the electrical lab for the first week of Electricity 101.

For free automotive electrical training, see Automotive Training and Resource Site . Once you are there, select online instruction. I have personally reviewed the material and it is very good. If you are new to automotive electrical troubleshooting, I highly recommend you spend a hour or so going through the material. You'll save at least that much time troubleshooting problems.

Using a Multimeter or DVM

Be careful, most cheap multimeters aren't capable of handling more that 10 amps. When you test current, the wires connected to the meter need to be the same size or larger than the wire that connects device under test to the power source.

Current (amps) is measured with the meter inline (series) with the device under test.
fig7_multimeter-series-measure-current.jpg


Most of the high current figures for radiator fans are the surge current figures. Any motor will draw -2-4 times the running current for about 1-2 seconds when it first starts spinning. That's why you use a slow blow fuse or a circuit breaker on a circuit that protects the wiring to a motor. Loads that have a lot of drag will draw higher current for a longer time when they first start up.

In automotive circuits, Voltage is measured from ground to power input of the device when it is turned on and operating.
fig6_multimeter-parallel-measure-voltage.jpg



Almost every meter has a different method for showing an open circuit. An open circuit is one with a break in it somewhere. That break can be a switch turned off, a fuse blown, a lamp burned out, a bad connector, a damaged circuit board or a cut or burned wire.

Without reading the instruction manual that came with your meter, I would not try to guess what your readings mean.

Step 1.) Find the instruction book that came with your Multimeter or DVM. Read it and familiarize yourself with how it works and how use it. If you lost the book or didn’t get one with it, do a Google search on the web to find the manufacturer’s web site & download a copy of the manual. Remember that while some meters auto-range to find the correct voltage range, the Ohms function ranges are usually set by the selector switch. Most of the resistance testing done in automotive troubleshooting uses the lowest Ohms range possible.

Step 2. ) Make sure that you know what test lead plugs into which jacks on the Multimeter or DVM. There are usually several different jacks on most Multimeter or DVMs, and they have different functions. Make sure that your battery(s) in the Multimeter are good: if you have any doubts, replace the battery(s).

Step 3.) Once you are sure that the Multimeter or DVM is functional and you have the leads plugged into the jacks for Ohms ( the Ω symbol), do some simple measurements to make sure that you know how to use it correctly. Set the switch to the lowest range and touch the leads together: you should not see “nothing” but you should see 0.3-1.0 ohms. Measure a 60 watt light bulb: cold it will measure about 17.5 Ohms. It you measure it while it is hot, the reading will be greater.

Step 4.) Make several test measurements using the ohms function and the DC volts function. Remember all resistance measurements must be done with the power off the circuit. This avoids false readings and possible damage to the ohmmeter.. Repeat steps 3 & 4 until you are sure that you can do it without making any mistakes.

Step 5.) Then see | Repair Guides | Understanding And Troubleshooting Electrical Systems | Basic Electrical Theory | AutoZone.com and carefully study ALL the information under the Heading Chassis Electrical, Basic Electricity – Understanding & Troubleshooting

Step 6.) Apply what you have learned and make the test measurements using the information in the wiring diagrams & my previous posts.

Don't be in too much of a hurry to bolt all the new, pretty, shiny parts together. Take the simple steps now and you will save yourself lots of time and trouble later.
 
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