???Gauges???

[super stang 10]

I have a 69 mustang and the gas and engine temperature gauges move when the car is started but the needles increase when you step on the gas and the oil pressure gauge does not work at all. I am getting power to everything as far as I know and I just bought a new voltage regulator thinking that would fix things but no luck. So if anybody has any tips or tricks to try I would greatly appreciate it. Thanks!

[Fordrevhead 29]

I would say weak grounds at gauges. When you rev up the engine they are getting more voltage and indicating probably closer to correct. Any weird issues with dim tail lights, etc? Check battery to chassis ground with ohm meter, if that's all good move right to the gauge cluster.

[LindenBruce 27]

Also, check to make sure you have proper grounding between the engine to the body of the car. That will also cause gauge issues. There should be a ground wire attached to the rear of the passenger side cylinder head and the firewall. If it's not there correct that also. Bruce

[danno 128]

After you have checked the ground connection, as suggested, then check the 12 volts when you are revving the engine up. The problem could also be the small voltage regulator on the back of the gauges. Do you have a volt and ohm meter?

 

For the oil pressure, a simple check is to put the ignition switch to the run position and have someone sit inside and watch the oil gauge. The someone else diconnects the connection to the oil pressure sender, down by the fuel pump. Take a nail and stick in in the wire connection that went to the oil pressure sender, and the other side of the nail to the engine. You should immediately see the meter start moving. If you see it start moving, you know the wires and meter are good. The problem is the sender. DO NOT do this for more than a 5 or so seconds, it can overheat the gauge.

 

Report back on what you find.

Danno

[Fordrevhead 29]

Also, check to make sure you have proper grounding between the engine to the body of the car. That will also cause gauge issues. There should be a ground wire attached to the rear of the passenger side cylinder head and the firewall. If it's not there correct that also. Bruce

 

 

By checking battery to chassis as I suggested it checks both the battery to engine and engine to chassis as there is no battery to chassis direct ground on these cars.

[LindenBruce 27]

By checking battery to chassis as I suggested it checks both the battery to engine and engine to chassis as there is no battery to chassis direct ground on these cars.

 

FRH,

You are mostly correct. As you state there is no direct ground path to the chassis for the majority of applications. I believe in 70 or 71 Ford started grounding the chassis via the batteries' negative cable on it's way to the engine in the area of the voltage regulator. Prior to that the only solid ground path from the engine to the chassis was the grounding wire at the firewall to the engine.

 

The engine and trans is isolated from the chassis via rubber motor mounts. Which in turn is further isolated from the chassis by the rubber insulators at the ends of each rear leaf spring. No real grounding path exists there.

 

Now, you will obtain some grounding effect through the radiator fluid as it connects the engine with the chassis where the radiator bolts to the radiator support. Coolant does conduct electricity, but oil does not. Nowever, that connection offers very high resistance that only gets higher as the coolant ages.

 

And that's why Ford added the grounding strap from the firewall to the engine. To enable a solid ground path for the gauge/sending units to operate. Because the gauges are grounded to the chassis at the dash assembly not to the engine. If the gauges were grounded to the engine you would see a two wire sending unit assembly with the second wire being the grounding wire. Without this ground path you will have erratic gauge readings if any at all. They may also read very high or very low. And may even change depending on engine speed and torque as per the throttle.

 

That's why I suggested to veryify the grounding strap connection. Without the grounding strap the gauges are basically operating inside of a Faraday cage, insolated from their sending units.

 

You are correct in suggesting the original poster to double check their connections at the gauges. As these too can become corroded or even loose afer time. Again offering inaccurate or erratic gauges readings.

 

Bruce

[Fordrevhead 29]

Bruce, I am familiar with the faraday cage as we sometimes have this "problem" with odd shaped parts when trying to powder coat. Same principle.

 

Anyway, to save time, I personally would still test the longest path (battery neg to chasssi) and if that's good then they're both good. If it's bad, then I would test each shorter path (neg to engine, engine to chassis) individually.

 

On later cars of course this doesnt work because there are multiple paths as we know and you must break connections to test them or others individually.

 

You say I am mostly correct, but then you fully agreed... if there is no chassis ground to the negative terminal directly (which on this vehicle stock there is not) and my method tests out, then the neg term to engine is in tact and so is the engine to chassis. If the gauges are grounded to the chassis and the sensors to the engine... no faraday cage.

[Trav_450R 10]

Could some of these problems be why my temp gauge doesnt work and my fuel gauge sometimes want to work and then it doesnt... the amp, speedo, and oil pressure work fine

[super stang 10]

After you have checked the ground connection, as suggested, then check the 12 volts when you are revving the engine up. The problem could also be the small voltage regulator on the back of the gauges. Do you have a volt and ohm meter?

 

For the oil pressure, a simple check is to put the ignition switch to the run position and have someone sit inside and watch the oil gauge. The someone else diconnects the connection to the oil pressure sender, down by the fuel pump. Take a nail and stick in in the wire connection that went to the oil pressure sender, and the other side of the nail to the engine. You should immediately see the meter start moving. If you see it start moving, you know the wires and meter are good. The problem is the sender. DO NOT do this for more than a 5 or so seconds, it can overheat the gauge.

 

Report back on what you find.

Danno

 

Hey thanks for the helpful tips! I just tried what you said and the gauges do move when you ground out the wires to the engine block. I did this with the oil and water temp gauges and I replaced the water temp sender and it is still acting crazy. So where did you say that I should put the volt/ohm reader to check the voltage regulator, just right on the regulator? And do you have any idea on how many volts I should be wanting to get from the regulator?

[super stang 10]

Bruce, I am familiar with the faraday cage as we sometimes have this "problem" with odd shaped parts when trying to powder coat. Same principle.

 

Anyway, to save time, I personally would still test the longest path (battery neg to chasssi) and if that's good then they're both good. If it's bad, then I would test each shorter path (neg to engine, engine to chassis) individually.

 

On later cars of course this doesnt work because there are multiple paths as we know and you must break connections to test them or others individually.

 

You say I am mostly correct, but then you fully agreed... if there is no chassis ground to the negative terminal directly (which on this vehicle stock there is not) and my method tests out, then the neg term to engine is in tact and so is the engine to chassis. If the gauges are grounded to the chassis and the sensors to the engine... no faraday cage.

 

 

Thanks for the info on the grounds. I just hooked up a new ground cable to help make sure that everything is grounding out properly, but I am still having some troubles. It must just have something to do with the voltage regulator. Ill keep working and ill try to let everybody know what I find