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What normally goes bad on the clock and fuel gauge on a 1972 Cutlass / A-Body?

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What normally goes bad on the clock and fuel gauge on a 1972 Cutlass / A-Body?

Old May 19th, 2019, 08:42 AM
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What normally goes bad on the clock and fuel gauge on a 1972 Cutlass / A-Body?

My clock was still working after 47 years when I bought my 1972 Vista Cruiser 4 years ago, but not anymore. Even then, it would sometimes just stop from time to time and needed some tapping to help it get started again. My guess is that it simply needs lubrication, but I wanted to check with people who have gone through this before to find out what kind of lubricant I should use and how much and where.

My fuel gauge was also working before I removed my gas tank for some rust repairs, but now the needle doesn't seem to move at all anymore. (After I took the fuel gauge apart and tested it in the car I realized that the needle probably just ended up pointed to the "HOT" position kind of randomly and that it didn't even seem like like there was any movement or any power going to it when I turn the ignition key). I took the fuel gauge cluster apart and didn't find anything unusual. The needle moves smoothly so my guess is that it's more likely the gauge is probably not getting any signal from the sending unit end? Does somebody here have a simple way of testing it without that special tester that's mentioned on page 12-23 of the Chassis Service Manual.

When I pulled the gas tank out there was one wire (from memory, the ground wire) that probably broke apart from the movement, so I soldered it back together again. I don't really think that I could have done anything wrong there. My original gas tank and sending unit looked pretty clean already, but I still thoroughly cleaned and rinsed it inside and out.

Thanks, Tom


Last edited by tcolt; May 19th, 2019 at 08:51 AM. Reason: add picture
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Old May 19th, 2019, 09:04 AM
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The fuel gauge needle moving past F like that is the classic indication of an open circuit. There should be two wires coming off the sending unit. One goes to ground, and you should make sure that that is securely connected and not corroded in the area where it connects to the frame. A bad ground is a common problem and would cause your problem. If the ground is OK, find where the other wire coming off the sender connects to the wire coming from the front of the car. I'm not sure exactly where it would be on a wagon, but this connection point is usually behind the fuel tank and behind the license plate. Pull that connector apart and ground the side coming from the front of the car. With the key ON, the needle should go to E. Remove the wire from ground, and it should go back to F or well past it. If it passes these tests, the dash gauge is fine as is the wiring leading to it, and the problem is mostly likely in the sending unit itself. Might be time for a replacement.
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Old May 19th, 2019, 09:34 AM
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AS Jaunty said your gauge pegging past full is an indication of an open circuit between the sender and the gauge. It can also be a bad sender. If you remove the sender wire at the tank and ground it with the key on, it should drive the gauge needle to E. If it does that then your problem is a bad ground at the sender or a bad sender.

The clock usually is just dirt spray som electronic parts cleaner inside the mechanism with out getting it on the face. Let dry and hook it back up to test.
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Old May 19th, 2019, 12:47 PM
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Thanks guys! I did that, but what happens when it goes to E, but doesn't go anywhere when I remove the wire from ground again. In other words the only electrical action I'm getting right now is the needle moving to E...
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Old May 19th, 2019, 12:56 PM
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With the key on if you ground the sender wire it should go to E, if the sender wire is removed it should go back to past full.
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Old May 19th, 2019, 01:46 PM
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Yes. So, does that mean for sure that either my positive wire or the sending unit are bad?

Darn. That means I have to drop the tank again :-(...
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Old May 19th, 2019, 02:51 PM
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If it does what I said in the post above then everything from where you grounded the wire to the gauge is good. The problem lies at the sending unit. Unfortunately dropping the tank is the next step. I know the wagon is a PITA.

When you have it down take the sender out of the tank and hook it up to the gauge and provide a ground to the ender body. See if it works by moving the arm.
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Old May 19th, 2019, 03:01 PM
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It doesn't. It does everything I said in the post above instead :-) Doesn't go back to F. I can't imagine why the sending unit would go bad just from carefully cleaning it, but I'll check the wiring first.

Thanks again!

Tom
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Old May 19th, 2019, 03:10 PM
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If the gauge is still not installed in the dash, it needs a ground to the case for it to work correctly. Try running a jumper and retest.
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Old May 19th, 2019, 07:16 PM
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What normally goes bad on the clock

Tom, if the electronic parts cleaner doesn't restore the clock function, look at the points. They may be stuck together or may look rough. Use a points file to smooth them. They get trashed when a battery is allowed to run down to deep discharge.
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Old May 20th, 2019, 01:54 PM
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Originally Posted by VC455 View Post
Tom, if the electronic parts cleaner doesn't restore the clock function, look at the points. They may be stuck together or may look rough. Use a points file to smooth them. They get trashed when a battery is allowed to run down to deep discharge.

Thanks Gary

I couldn't find any contacts or any kind of wind-up mechanism that might be powered by those coils? I thought this was an electronically powered (quartz) clock, not electro-magnetic wind-up?... (See pictures.)

Is there a particular type of lubricant you use on clocks?



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Old May 20th, 2019, 03:05 PM
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Originally Posted by tcolt View Post
I thought this was an electronically powered (quartz) clock, not electro-magnetic wind-up?... (See pictures.) Is there a particular type of lubricant you use on clocks?
Tom, the pictures are of a mechanical clock. The electro-magnets are in the first picture. The spring is in the second picture. It is a rotary spring wound between horizontal plates underneath the large gear at top. One end of the spring is attached below the hex-shaped support for the mechanism cover.

It looks as though there has been some heat damage in the clock. This is what happens when the battery runs very low--the contact closes but there is not enough voltage to wind the clock. The contacts stay closed and the remaining amperage from the battery fuses the points and tries to fry the electro-magnets. There are YouTube videos about how to fix these clocks.

When you get everything fixed mechanically and freed-up with electronic parts cleaner, spray AMSOil MP on the moving parts and blow away the excess with compressed air or canned electronic Dust-Off. The MP is mostly solvent that leaves behind a film of very low viscosity synthetic lube. There won't be enough lube to attract dust but will be enough to keep the parts moving freely for many years.
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Old May 20th, 2019, 03:45 PM
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Originally Posted by tcolt View Post
I thought this was an electronically powered (quartz) clock, not electro-magnetic wind-up?
In a Cutlass in 1972? Not a chance. Olds didn't offer quartz clocks until the 1974 model year, and then it was standard only in the Toronado while it was an extra-cost option in the 88 and 98. I don't know when a quartz clock was offered in an A-body, if it ever was.
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Old May 20th, 2019, 04:20 PM
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If you have carefully cleaned the sender unit, you might have inadvertently moved the wiper arm off the resistor. It should be easily bent back to touch firmly, but not too firm.
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Old May 20th, 2019, 05:58 PM
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Darn. I see it now and it looks like there is more damage than I can fix. One of the wires to the coil was disconnected (burned) which probably means that the whole coil is fried and the reason I couldn't figure out how the thing winds up was because the contacts seem to be pretty welded together. I might have to live with a broken clock or hope that a salvageable one is available cheap.

Eric, I think I've checked the wiring as much as I can although I just looked at the wiring diagram and the set-up for the fuel gauge is pretty simple. It looks like I should be able to measure the resistance between the other end of that wire that we had disconnected (it's below the left-hand taillight on a wagon, Jaunty) to check for any continuity. Right now, it seems it should read open circuit (infinite Ohms), since the gauge isn't getting any signal (only goes to empty when shorted, but not in the other direction.)

Thanks, Tom
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Old May 20th, 2019, 06:04 PM
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Originally Posted by Yellowstatue View Post
If you have carefully cleaned the sender unit, you might have inadvertently moved the wiper arm off the resistor. It should be easily bent back to touch firmly, but not too firm.
It's possible and goes together with "open circuit"

Jaunty. Yeah, I didn't trust my initial reading of what I thought looked like a wind-up clock, but nothing moved (wound up)... At least quartz wasn't too far off year-wise. I like the mechanical clocks better anyway because you can often fix/ save them...
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Old May 21st, 2019, 04:29 PM
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Does anyone have a clock core that I could repair or maybe take the coils out of to fix mine? I already have an inquiry into Scott and he's checking his supply, but he also has a really nice restored clock with Quartz movement for somebody who doesn't want to go the difficult route like me :-)...
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Old May 22nd, 2019, 09:14 AM
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Originally Posted by tcolt View Post
Does anyone have a clock core that I could repair or maybe take the coils out of to fix mine? I already have an inquiry into Scott and he's checking his supply, but he also has a really nice restored clock with Quartz movement for somebody who doesn't want to go the difficult route like me :-)...
You've already contacted Scott which is one of my 2 resources for gauges. If he doesn't have what you need call Frank Chiechi at 631-899-1301. Scott knows him well. He will rebuild your original like new. If you want you can tell him Mike Sarro gave you his contact info.
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Old May 23rd, 2019, 12:03 AM
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Thanks Mike. Both great guys. I already contacted Frank and I'm getting a clock from him. Turns out, my clock was by a rare manufacturer and parts are hard to come by so I had to go with a new (rebuilt) one..

Last edited by tcolt; May 23rd, 2019 at 12:26 AM.
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