Wacky guages
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Junior User
Joined: Oct 2006
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Wacky guages
Anyone care to take a shot at diagnosing this problem. Both my temperature and my fuel guages are acting strangely, and neither are registering correctly. With the truck running, both guages go all the way to their respective end points, i.e., fuel guage says full, temp says hot.
I've replaced the instrument cluster voltage regulator, and at least for the fuel guage I'm fairly confident--but not sure--that the sending unit is working correctly. I don't know how to check the temp sending unit.
Any thoughts?
I've replaced the instrument cluster voltage regulator, and at least for the fuel guage I'm fairly confident--but not sure--that the sending unit is working correctly. I don't know how to check the temp sending unit.
Any thoughts?
Postmaster
Joined: Nov 2001
Posts: 3,351
Likes: 1
From: Escondido, CA
Try placing a meat thermometer on the water crossover passage on the intake manifold. Then you can also use it to check your radiator cooling by gentlely sticking it between the fins at the top and bottom near the tanks. That is a waking thought by the way. It may or may not work but the gauge goes up to a few hundred degrees.
Another option is an lazer temp tool. Try not to open the system up since the cap helps to keep the fluid from boiling by increasing the pressure.
Also how are the chassis grounds? Make sure the grounding wires or straps are in good shape. Any kind of corrosion in there will make the resistance go all over the place. The both systems use grounds to complete the circuit.
Another option is an lazer temp tool. Try not to open the system up since the cap helps to keep the fluid from boiling by increasing the pressure.
Also how are the chassis grounds? Make sure the grounding wires or straps are in good shape. Any kind of corrosion in there will make the resistance go all over the place. The both systems use grounds to complete the circuit.
Postmaster
Joined: Dec 1999
Posts: 2,813
Likes: 6
From: Connecticut
Add a ground from the cluster to a good spot on the firewall or other good metal ground. Make sure the temp sending units on the block don't have teflon tape on the rthreads as it inhibits the ground. With the key on and not running, breifly ground the wire from the temp unit in the block and watch the dash guage. It should go to full. If it does, that eliminates a bad guage. Do the same with the wire from the gas tank unit. If it goes to full, the dash unit is good also.
Is this a recent problem, or has it been going on for a long time? Check the CV unit with a volt meter. Test the side going in, it should read 12V. Then test the other side, it should read 6V +/- . Ford guages are made to work on 6 volts. If you're getting more that 6 volts ( 8-12V) then it's bad. I would suspect that, I've gotten bad ones, especially aftermarket auto parts store ones.
Barry
Is this a recent problem, or has it been going on for a long time? Check the CV unit with a volt meter. Test the side going in, it should read 12V. Then test the other side, it should read 6V +/- . Ford guages are made to work on 6 volts. If you're getting more that 6 volts ( 8-12V) then it's bad. I would suspect that, I've gotten bad ones, especially aftermarket auto parts store ones.
Barry
Posting Legend
Joined: Sep 2001
Posts: 30,255
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Actually the gages run on 5V average voltage but you need an oscilloscope to read it. The instrument voltage regulator is like a turn signal flasher unit turning the power to the gages on and off.
When both gages go high like that the cause is the instrument panel voltage regulator loosing it's ground connection or it is bad. Since it has been replaced it is probably the ground connection.
When both gages go high like that the cause is the instrument panel voltage regulator loosing it's ground connection or it is bad. Since it has been replaced it is probably the ground connection.
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Junior User
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Ah ha! The voltage regulator is not grounded. In my truck, when I replaced the regulator it was not attached to anything. I've figured out that it should be attached to the instrument cluster. I'm looking forward to trying this out in the morning.
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Junior User
Joined: Oct 2006
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Well no such luck. I cleaned all the contacts, and attached the regulator to a good ground. Now the guages don't register at all.
Banjopicker--I got your phone message. Thanks, I'll give you a call, and I would love to drop by Friday or Saturday at your convenience. Regards.
Banjopicker--I got your phone message. Thanks, I'll give you a call, and I would love to drop by Friday or Saturday at your convenience. Regards.
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Posting Legend
Joined: Sep 2001
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The voltage regulators have three terminals. One is battery voltage, another goes to the gages, and the third one is the case that goes to ground.
With full voltage going to the gages it is possible they are burned out or the senders damaged..
With full voltage going to the gages it is possible they are burned out or the senders damaged..
Last edited by Torque1st; Nov 23, 2006 at 10:52 PM.
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Laughing Gas
Joined: Aug 2006
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From: mountaintop, Pa
I have this issue also. When you key on does your ALT light go on. My oil light goes on but not the alt. I measured groung to the socket and it's good and voltage that good the lamp is good. I think I have a ground ing issue. I know good ground good voltage I should have a light but no.
I did get it to light up if I ground lamp to cluster?? I have 2 un-connected wires back there. One is black and the angled style the other is a barrel type.
I wonder if the cab is grouned to frame or is the fuse box supposed to ne grounded??
I'm not trying to hijack, but add things I've done.
Am I assuming correct that "key on" should turn on the alt light???
please post if you get it.
bob
I did get it to light up if I ground lamp to cluster?? I have 2 un-connected wires back there. One is black and the angled style the other is a barrel type.
I wonder if the cab is grouned to frame or is the fuse box supposed to ne grounded??
I'm not trying to hijack, but add things I've done.
Am I assuming correct that "key on" should turn on the alt light???
please post if you get it.
bob