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Old 03-10-2013, 05:20 PM   #1
msg
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66 c10 electrical/cluster q's

I was hoping to fix the cluster on my 66, but do not have alot of electrical experience.

Here is whats going on.

What are the best ways to fix these?

speedometer= does not work

temp = just stays at Cold

battery = stays in the middle even when disconnected

oil = it seems to work, when running the needle goes mid way

fuel= kinda works. when full it goes to F and then as I get around a half tank it moves quickly back and forth the whole time. I checked to see if the wiring to the fuel tank was maybe touching the chassis and grounding out but throughout the length of the wire didnt see any exposed wire.

The Tandem Lock light = stays on all the time. I recall the guy I bought it from telling me that that light should go out when the engine is revved up and that if it didnt the battery would run down. It has cut off in the past but recently it just stays on. Should I just pull the bulb from it?

I was wanting to add a tach and vacuum to the cluster but figured all the other gauges should operate correctly first.

Anybody have suggestions on how to get this all working right?
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Old 03-10-2013, 10:31 PM   #2
pmkrew
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Re: 66 c10 electrical/cluster q's

Sounds like youve got some wiring to sort out.
Have you checked to see if the cable is good on the speedo?
Where are you in GA?
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Old 03-10-2013, 11:03 PM   #3
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Re: 66 c10 electrical/cluster q's

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Originally Posted by pmkrew View Post
Sounds like youve got some wiring to sort out.
Have you checked to see if the cable is good on the speedo?
Where are you in GA?
I'm in Newnan and so new to electrical that I didnt know which place I should start considering all of the things going on. Debating on buying a new wiring harness and update this whole thing.

How should I check the speedo cable? Try and disconnect from the dash and drive around and see if it spins inside the cable?
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Old 03-11-2013, 12:15 AM   #4
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Re: 66 c10 electrical/cluster q's

Driving around with the cable off isn't the best way. The easiest way is to take the end off the trans and attach it to a drill and see if the speedo moves. Is it does then you know it's the gear in the trans. Easy change. Plastic piece that just slides out. If the speedo doesn't spin then disconnect the cable from it and spin it again. If it spins then its the gear or something with the speedo. If it doesn't , well then its the cable. Your fuel gauge is probably the float inside the tank. It works off of electrical resistance and when there is more room for it to bob around more plus it being old and worn I'm sure there's slop. As far as your temp goes you'll have to check that wire for shorts. If you don't find any then it's probably the sensor. It works off of resistance as well. The hotter it gets the more resistance and that's what the needle shows you translated into temperature. Unfamiliar with the tandem lock sorry.
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Old 03-11-2013, 12:40 AM   #5
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Re: 66 c10 electrical/cluster q's

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The easiest way is to take the end off the trans and attach it to a drill and see if the speedo moves.
Will give this a try thanks!

Quote:
Your fuel gauge is probably the float inside the tank. It works off of electrical resistance and when there is more room for it to bob around more plus it being old and worn I'm sure there's slop.
Is it fixed by replacing the float or adjusting somehow?

Quote:
As far as your temp goes you'll have to check that wire for shorts. If you don't find any then it's probably the sensor. It works off of resistance as well. The hotter it gets the more resistance and that's what the needle shows you translated into temperature.
Ill try this thanks.

Quote:
Unfamiliar with the tandem lock sorry.
I searched and found this thread, but again the solution was an incorrectly inserted bulb, which for me isnt the issue. I wonder if removing the bulb is a good idea?

http://67-72chevytrucks.com/vboard/s...d.php?t=276896
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Old 03-11-2013, 08:23 AM   #6
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Re: 66 c10 electrical/cluster q's

If you have a C10 with a 'tandem lock" light on- someones got a bulb in the wrong socket. That is more likely a generator light that should come on with just the key "on" then go out after the engine starts. if it stays on, you may have a charging issue.
Alot of times an erratic fuel guage is attributed to a failing sending unit in the tank- in other words the reostat portion is worn and not always making a good contact , internally. Again, this is sometimes, not always
Another guess would be that someone put a guage cluster in a truck that originally have indicator lights and did not change all the sending units.
the oil pressure is mechanical.
To test the temp wiring and guage- take the wire off at the sending unit. Note if there are 2 wires(lt green and dk green)then it originally had a light- you will want the dk green wire. Ground the wire to the engine block. Momentarily turn the key on-if the needle goes to hot- then the wiring and guage are good. If nothing happens, first check the fuse for either "panel" or "instruments" .

I'd test the speedo as mentioned above- note that you will need to run the drill in reverse, I believe.
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Old 03-11-2013, 08:29 AM   #7
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Re: 66 c10 electrical/cluster q's

Also to help you figure out which light is which, refer to a wiring diagram-it'll give you the wire colors for each socket.
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Old 03-11-2013, 12:19 PM   #8
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Re: 66 c10 electrical/cluster q's

Quote:
if it stays on, you may have a charging issue.
Since the light does now stay on when it used to go out when the engine is revved up, would this likely be due to the electric choke that is wired from the alternator vs. an ign unfused connector from the fuse box?

I had this thread going when I attempted to disconnect the connector from the alternator and it snapped the white wire. I have since replaced with a new connector and wired it back up the way it was for now.

http://67-72chevytrucks.com/vboard/s...d.php?t=567471

Since then I have been looking for a spot to run from directly to the electric choke as vette vette suggests in the thread, but the to ign unfused connectors are taken. One is the large white wire that connects to the HEI distributor, and the brown wire was spliced and the red/white wire and runs to the radio. Since the cig lighter is not working I was thinking to disconnect it. Could the electric choke be run from that? Looking for ideas on how to solve that.


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Old 03-11-2013, 02:27 PM   #9
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Re: 66 c10 electrical/cluster q's

You don't want to run the choke off the cig lighter circuit, because it is hot all the time,even with the key off, and shared with the dome light.
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Old 03-11-2013, 04:57 PM   #10
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Re: 66 c10 electrical/cluster q's

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I'd test the speedo as mentioned above- note that you will need to run the drill in reverse, I believe.
You are correct, sorry I forgot to mention that.
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Old 03-11-2013, 05:09 PM   #11
Rich 5150 69
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Re: 66 c10 electrical/cluster q's

It sounds to me that some PO had switched a gauge panel in for standard idiot light panel, so with that he would need the gauge harness, and correct temp sender for the gauge.
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Old 03-11-2013, 06:00 PM   #12
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Re: 66 c10 electrical/cluster q's

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Originally Posted by Rich 5150 69 View Post
It sounds to me that some PO had switched a gauge panel in for standard idiot light panel, so with that he would need the gauge harness, and correct temp sender for the gauge.
Having trouble following, do you mean that the gauge harness and temp sender are likely incorrect?
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Old 03-11-2013, 07:17 PM   #13
Rich 5150 69
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Re: 66 c10 electrical/cluster q's

Standard panel vs gauge panel use a differant harness, you can get the temp sender and harness thru the Truck and Car Shop, not totally saying this is what happened, but what happened to me when I had purchased mine, all they hooked up was oil pressure gas and speedo. the temp was wrong ( harness and sender.
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`64 C10 vortec 350/350/373 posi
`69 RS/SS 350/350/308
`37 Ford 406/350/324 traclock
`68 Dart 370/904/323 suregrip
Kids in the back seat may cause accidents, accidents in the back seat may cause kids, so no back seats no accidents.....

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Old 03-16-2013, 01:54 PM   #14
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Re: 66 c10 electrical/cluster q's

Unhooked the speedo cable from the transmission and best I can see this is normal on the inside



Then the end of the cable looked like this



and when I hooked up the drill and put the drill in reverse the cable spun inside the sleeve and began to slide out of the sleeve as if it were not connected at all to the back of the cluster.



Does this mean the cable is broken at the back of the cluster?
Or just not hooked up properly?
What next?
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Old 03-17-2013, 11:47 PM   #15
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Re: 66 c10 electrical/cluster q's

Yeah I imagine you've checked the backside of the speedo gauge by now. It could actually slide out because the cable has to be able to move inside the sleeve. Shouldn't be a problem to slide it back in. It shouldn't be hard to keep it from sliding out again with just a little bit of force. Also I believe what Rich is trying to say is that someone tried and failed at upgrading your gauge cluster to a newer one and that is why nothing is wired up correctly. Your harness is (original) older than your cluster.
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Old 03-18-2013, 12:27 AM   #16
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Re: 66 c10 electrical/cluster q's

Yeah, I removed the cable from the back of the cluster and these parts fell out




Guess it's best to get a new cable.

I bet Rich is right, this thing is kinda messed up.
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Old 03-30-2013, 11:50 AM   #17
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Re: 66 c10 electrical/cluster q's

Bought a new cable and installed it, then I did the reversed drill attachment test and it made a racket in the speedometer but the needle was moving. I lowered the rpms and it still has a clackety sound in there.

Took it for a drive and the sound was drowned out a bit by the motor/road noise but its there. Even noticed that the needle didnt glide but was shaking a little as it went.

I removed and took apart the cluster and cleaned things up and checked the speedo to see if anything was lodged in that might be making the sound and saw nothing. The needle itself seems to be the racket making vibrations. Is there some kind of bushing that it should have at the needle base? Cause its pretty open down there.

Anyone ever run into this? Does this mean I should replace the speedometer or is there a potential fix?
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Old 03-04-2015, 11:02 PM   #18
mjs94080
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Re: 66 c10 electrical/cluster q's

Im having the same problem......

When Im in 1st gear, speedometer needle wont spin.
On 2nd, it will spin.
On 3rd, it will spin.

Any advice?
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Old 03-05-2015, 12:36 AM   #19
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Re: 66 c10 electrical/cluster q's

I was having issues with the cluster and the speedometer making a clackety racket. The racket was solved by a local garage that I had taken it to have a 700R4 installed. He told me that I did fine making the connections from the back of the speedometer to the trans, but what I didnt do was grease up the cable first. As for the rest of what I was dealing with its all in a pile in the garage as I have started to break it all down and learn to restore it.

The wiring was in bad shape. I took some of the plastic coating off a few and each one was gummed up allthroughout, not shiny copper, not even close. The fuse panel was pretty rusty as well so I will be buying a new fuse panel and wiring harness once I get the frame and body redone.

I'll be revisiting Rich's comment once Im at the point of buying that harness and figuring out what the difference between standard and gauge panels.

Quote:
Originally Posted by Rich 5150 69 View Post
Standard panel vs gauge panel use a differant harness, you can get the temp sender and harness thru the Truck and Car Shop, not totally saying this is what happened, but what happened to me when I had purchased mine, all they hooked up was oil pressure gas and speedo. the temp was wrong ( harness and sender.
Until then I have my hands full, started a build thread here.
http://67-72chevytrucks.com/vboard/s...d.php?t=623848
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