Gauges messed up

[WVUexplorer]

Ok so i just redid my head gaskets on my 92 4.0L and everything seems to be running fine but i have an error with my alternator, temperature and oil pressure gauge. my alternator gauge is reading lower then normal even though it's pushing 14v at the battery, and the temp and oil gauge rise significantly when a load is put on the electrical system (window motor, locks, brake lights). so i believe there is something wrong with a connection but i don't know. but it might be something else, when playing with my vacuum lines i noticed that when i disconnected some of the lines the gauges would start to move back to their normal spots but then jump back to un normal position.

Coolant level is good so i don't believe i am over heating (when the engine is hot, turned of and key is in run position temp reading straight up normal).

Any suggestions would be greatly appreciated.

 

[arco777]

Oil pressure gauge is just an idiot light type - if it's good (above 5psi I believe) then the oil gauge will read about the same as the battery voltage gauge. These gauges are not real precise or well calibrated so if your voltages are reading good with a multimeter, don't sweat it.

Coolant gauge shouldn't be affected by input voltage so much but it can be if your voltage is fluctuating a lot. Check your voltage regulator. The coolant gauge is pretty simple, just a ground, a signal (varying resistance of sender) and 12v hot in RUN.

 

[WVUexplorer]

I understand it is an idiot gauge so it worries me when it's reading off the charts (H+) and the alternator gauge is a 1/4 above low. And both the temp and oil pressure gauge increase dramatically when an electrical device is used. I know i have coolant and that it is circulating so i don't understand why these gauges seem connected and are off.

 

[arco777]

If I were you I would check with a multimeter exactly what the gauges are seeing. Gauges themselves can go bad, so can senders.

If you pull the dash bezel off, then the plastic-glass face off the instrument cluster (leave cluster in) and the black inner bezel of the cluster, you can pull the gauges out. Then you have access to the slots the gauge pins plug into. With the car running or key in RUN position you can stick your multimeter probe right into those slots and see the real reading. Verify the resistance values you get at the connector for the sender against a chart showing what you should be reading. Verify voltages for supply are correct.

Then you know if your gauge is bad or not. If your resistance is out of spec, follow the wire back to the sender, probing it at several points to see if there's an anomaly somewhere. Check resistance readings of the sender itself. If the gauge feed voltage is bad, backprobe that and see if it's a widespread problem with the electrical system, like a failing voltage regulator.

I'll try to find you charts for sender resistance values.

 

[snoranger]

Sounds like you have a bad ground some where. The chances that all your gauges went bad at the same time arent very good. I'm going to assume, by the way you worded your 1st post, the problem started after you did the head gaskets. I'd start looking over everything you touched when you did the head gaskets.

 

[arco777]

See the attachment.

What I read from this about the two gauges (correct me if I'm wrong).

Water temp gauge operates on resistance values from the sender, which is near the water neck. 74 ohms is listed as the approximate HOT mark reading and 9.7 ohms for cold. An internet search reveals this is common for many Ford coolant gauges. I suppose you could check gauge calibration by using resistors instead of the sender input.

I haven't yet found a specific chart for the sender but will keep looking. Don't confuse it with the Ford ECT sensor, which reports to the PCM and has a different set of values. Easy to find charts for the sensor, but not the sender.

Oil pressure is a switch, not a real sender, as is well known on the board. You can see it uses a 20 ohm resistor as the gauge signal. The gauge itself is capable of displaying a real range of movement but is wired up to only show on or off. It appears there is no wiring to indicate abnormally high oil pressure.

Hope this helps.

 

[WVUexplorer]

Thank you all so much for the help but I have fixed the problem. This is a very embarrassing mistake but I'm glad it is fixed.

When I was putting everything back together I would place screws and bolts in there proper place but not tighten them in order to make sure everything was in it's right place. So when it came time to tighten it I missed the nut for the wire connecting the cylinder head to ground. So the wire was making a very loose connection causing all my gauges to go haywire.

Thank you all so much for your suggestions and hard work, hopefully the information you provided will assist others in their time of need as it has helped me.