2000 Super Air PCM 350 Gauge Wiring

[T_Bone17]

I am trying to find better information or a diagram for the dash gauge wiring on a 2000 Super Air with the PCM 350.

I have replaced all of the gauges, but the engine temp, and oil pressure still do not work.

One possible cause is, it looks like they were replaced by the previous owner, and I only copied the wiring that was currently at the gauges, so that could have been wrong to begin with.

Or some of the wiring is bad/wrong, or the sensor/sending unit is bad.

But I do not know where the sensor/sending units are located, or what wires should be where.

If anyone could give me some direction that would be great.

There are diagrams for the GT-40, but not for the PCM, I know it is one of a few 2000's with the factory PCM.

[Blamey]

I am trying to find better information or a diagram for the dash gauge wiring on a 2000 Super Air with the PCM 350.

I have replaced all of the gauges, but the engine temp, and oil pressure still do not work.

One possible cause is, it looks like they were replaced by the previous owner, and I only copied the wiring that was currently at the gauges, so that could have been wrong to begin with.

Or some of the wiring is bad/wrong, or the sensor/sending unit is bad.

But I do not know where the sensor/sending units are located, or what wires should be where.

If anyone could give me some direction that would be great.

There are diagrams for the GT-40, but not for the PCM, I know it is one of a few 2000's with the factory PCM.

PCM is the engine Brand. Both the 350 and GT40s are PCM engines. The 350 should have a model name Apex or Excel or something like that.

Have you looked at the different manuals in the reference section for details?

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[T_Bone17]

It is the Apex.

I have looked through the diagrams in the reference section. Nothing that matches up with the wiring I have.

[DW SD]

Temp sender will be in the water pump.

One way to check the gauge is ground the sender wire and see if it pegs.
Then go open circuit. It should peg the other way.

If the gauge works then check continuity between sender and gauge on the sender wire.

This troubleshooting method will Work for both gauges / senders.

In the end the sender and gauge need to be matched. But not necessarily matched to engine except for threading properly. With this vintage of engine it is likely pipethread and might interchange between ford and chevy engines.

Each gauge will also have 12V+ switched, ground, a light for illumination and the gauge sender wire.
Those first three will be consistent across all gauges.

For that reason you might not need a wiring diagram.

Doug


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[DW SD]

Temp sender will be in the water pump.

One way to check the gauge is ground the sender wire and see if it pegs.
Then go open circuit. It should peg the other way.

If the gauge works then check continuity between sender and gauge on the sender wire.

This troubleshooting method will Work for both gauges / senders.

In the end the sender and gauge need to be matched. But not necessarily matched to engine except for threading properly. With this vintage of engine it is likely pipethread and might interchange between ford and chevy engines.

Each gauge will also have 12V+ switched, ground, a light for illumination and the gauge sender wire.
Those first three will be consistent across all gauges.

For that reason you might not need a wiring diagram.

Doug


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[T_Bone17]

I am gong to try that. See what I come up with.

Looks like the 2001 wiring is similar. Just switched from a dark blue signal wire on the oil pressure to a light blue. And a dark brown to tan on the temp signal wire.

should the gauges peg when grounded(granted there is continuity) at the sending unit. With just key power on? Or does the engine need to be running. Boat is still winterized, and don’t plan on de-winterizing it for a few more months. So can’t start the motor right now. But would like to get these gauges working for next season.

[DW SD]

Engine doesn’t need to be running.

You can use a jumper wire to test. I have a set of wires with alligator clips on each end for such testing

First step could be at the gauge. Clip the sender connector to ground. Turn ignition to on without starting.

To test open circuit just remove the sender wire and create an open circuit at the gauge.

The needle should peg each direction based on ground vs open circuit.


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[T_Bone17]

Went to test the gauges. Grounded out the signal wire - nothing.

Wanted to make sure they were getting power - they weren't

Ran a jumper wire directly from the battery to the power terminal on the back of the gauge, then grounded out the signal, both gauges peg both ways - gauges are functioning

In the process of doing that, when I applied power to the gauge directly from the battery, something turned on in the back, connected to the fuel filter canister. Not sure what it is, fuel pump would be in the tank right?

That seems really wrong?

Tested continuity from the power wire at the gauge to the red wire at this thing, and I get 95 ohms.

See pic

[Blamey]

Went to test the gauges. Grounded out the signal wire - nothing.

Wanted to make sure they were getting power - they weren't

Ran a jumper wire directly from the battery to the power terminal on the back of the gauge, then grounded out the signal, both gauges peg both ways - gauges are functioning

In the process of doing that, when I applied power to the gauge directly from the battery, something turned on in the back, connected to the fuel filter canister. Not sure what it is, fuel pump would be in the tank right?

That seems really wrong?

Tested continuity from the power wire at the gauge to the red wire at this thing, and I get 95 ohms.

See pic

Looks like a low pressure fuel pump to me. I am not familiar with the Apex but the low pressure pump on my GT40 looks like what you circled.

The big cannisters to the left is your FCC which is a fuel filter and High Pressure Fuel Pump.

With my GT40 these both prime when the key is turned on.

If these are not normally priming. Then you have a wiring issue at the dash.

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[DW SD]

Cool. you figured out the problem. Now...
You need to find switched power at the dash and wire them to the broken gauges. Is that the purple wire in the dash, which gets power with the ignition switch? Odds are, one of the daisy chain connectors broke.

And that is good that your fuel pump is turning on to prime with ignition. Thats what it is supposed to do.

If you have a test light, use it to find switched power in the gauge panel (and determine color of the gauge 12V+ source). Then you could use that source to power the other two gauges. Again, I'm guessing one of the wires broke that daisy chain power to the gauges. Daisy chain means... power is supplied to one gauge, then the female spade connector that supplies the original source also has power for the next gauge attached. Same with the next gauge... and the next.
This is in lieu of wiring all gauges to the original power source. That is why two go out at once. One broken wire or connector breaks everything downstream.

Doug

[T_Bone17]

I will look for any broken connections at the gauges.

Just to clarify, that pump turns on constantly, when power is supplied to the power (purple) wire at the gauge. Directly from the battery. Not with the key power on or anything. And it doesn’t t just prime it stays on the entire time I leave that wire connected. Didn’t want to leave it on there too long in case it would burn it out or something.

[DW SD]

Yes, you are probably back-feeding the fuel pump somehow from the gauge.

Do you have a test light? If so, test for 12V+ at the gauge when the ignition is switched on. Also compare to other gauges.

I'm guessing the two broken gauges have lost 12V+ switched power

Doug

[T_Bone17]

Tested for ignition power at the gauges.

I do not have any ignition power at them.

The purple wire that is supposed to be ignition power has nothing.

It must work when the motor is running because my other gauges work when the boat is running.

don't want to test that tight now, as the boat is still winterized.

I checked that purple wire back at the 7 pin connector at the motor, nothing there either.

[DW SD]

The purple wire should have power when ignition is on. Whether engine is running or not. You will need to turn the key to the point of ignition on.
OR
If you have the soft switches... do this. push the on / start button twice. But just tap the second time. If you do it fast enough, the starter won't even crank.

In short, do the same as when you heard the fuel pumps run. That is ignition on. Then test for 12V+ at the purple wires.

I'm guessing the two dead gauges either don't get power at ignition on or are broken. But from your earlier notes, I think they aren't getting power at ignition on.

Doug

[T_Bone17]

I have the soft switches. I assumed "ignition power" would be on when I put in the code and hit start once. Didn't know I needed to bump it a second time. That could be why there was no power at the purple wire. I will try the second bump thing, and test the wire again.

I did find the majority of the problem. The signal wires for the engine temp and oil pressure were switched up. According to the wiring diagram, they were correct, but traced them back to the sending units and they were opposite. So with that sorted they should work now, granted the sending units are functioning and if they aren't, should be an easy fix.