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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

figure this out!!

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Old Apr 12, 2006 | 09:59 AM
  #1  
bigredman's Avatar
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Question figure this out!!

With the headlights on, when I turn the turn signal on the tachometer pegs back and forth as the flasher turns on and off. It doesn't do it with the headlights off. Also, when it is cold outside, the tachometer doesn't work. It sticks in one spot. but it only does this when it is cold outside.
These arent anything important, but I would like to fix it.
Any help will be appriciated.
 
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Old Apr 12, 2006 | 10:18 AM
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I would suspect a multifunction siwtch (combination turn signal and headlight control)...what year is your truck?
 
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Old Apr 12, 2006 | 11:22 AM
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may be a bad pc "board" on the back of the cluster, all those circuits run through it, and they may be shorting across, but when warm, they move away from each other, no longer shorting out.
 
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Old Apr 12, 2006 | 02:12 PM
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Fellro has a good suggestion.

I would also check the connector to the cluster. Make sure the wires are not rubbing together at the connector, and make sure the pins and connector are seatted correctly in the cluster. The pins are close together and could be moving about touching other contacts they are not supposed to. Also check the ground to the cluster. Bad grounds can cause all sorts of weird problems as you describe.

As for the tach, you could try and put a little drop of oil such as WD-40 on the shaft that goes inside the tach that the needle attaches to. If you put too much you could blow, or short out the tach though so be careful.
 
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Old Apr 12, 2006 | 02:34 PM
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Be sure to clean/check the ground wire connections between the firewall and engine block and the negative battery terminal and engine/frame.
 
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Old Apr 14, 2006 | 01:05 AM
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The tach not working when cold is most likely a mechanical problem in the tach.

Does the tach act up using the right and left signals?
I'm thinking that your printed circuit is not grounded properly so the signal is feeding back through the ground side of the tach. Are the signal idicator lights on the dash dim? I would expect so if I'm right about the ground.

As Piffery says, ground the firewall to the block and chassis. But also make certain that the printed circuit has a ground if that doesn't cure it.
 
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Old Apr 14, 2006 | 01:59 AM
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The mounting screw for the tab of the instrument voltage regulator is a good place to connect an external ground wire from the metal dash panel support or firewall.
As Bdox says, it can clear up lots of strange problems with gauges and lamps.
 
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Old Apr 14, 2006 | 09:32 AM
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My truck is an 86. Yes, the tach pegs with both left and right turn signals. And with the sticky tach, if I drive around for a while with the heater on, when the cab warms up the tach starts working again. Maybe it needs lubed up?
Thanks for the input.
 
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Old Apr 14, 2006 | 09:45 AM
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I don't think that you lube those. The lube collects dirt/dust and gums it up. Probably some contact cleaner and one of those cans of compressed air to clean it out.
 
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Old Apr 14, 2006 | 01:40 PM
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I was grasping at straws at the lube part, a sticky return spring I imagine.

A dry lube that doesn't collect dirt perhaps.

A seperate ground wire from the voltage regulator, hold down screw, to the dash frame metal, is a great idea. may do that to mine.
 
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Old Apr 14, 2006 | 02:43 PM
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Surely that tach is a jeweled pivot, like in a Rolex.

Seriously though, I don't think it should be lubed. Just clean.
 
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Old Apr 14, 2006 | 06:17 PM
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Originally Posted by Bdox
Surely that tach is a jeweled pivot, like in a Rolex.

Seriously though, I don't think it should be lubed. Just clean.
LOL,

You're right it shouldn't be lubed, but if it doesn't work and/or it's sticky, it wouldn't hurt it much if it was. IMO.

Hmmmm... It acts like to me that if the tach was lubed at the manufacturer/ or if somebody sprayed lube into it before, that it is getting cold and becoming sticky, or that it's worn out and has a flat spot, and when it heats up the expansion releases it. I can't see much dust and dirt getting into the tach, in the cluster.

If you lube it, it could make it work like new, it could also blow it up, and finish it off, or it will work the same as it does now. Be prepared for any eventuality, like that.

If only you could open the thing up, but you can't. It's a sealed unit.

What he really needs is a new tach, all being proper etc...
 
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Old Apr 14, 2006 | 08:42 PM
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That problem too, may clear up once the ground(?) problem is resolved since the tach needs a good ground reference to work. I wouldn't go squirting anything in the tach until the other issues are resolved and all the tach wiring has been checked out.
 
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Old Apr 15, 2006 | 01:37 AM
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Originally Posted by Piffery1
That problem too, may clear up once the ground(?) problem is resolved since the tach needs a good ground reference to work. I wouldn't go squirting anything in the tach until the other issues are resolved and all the tach wiring has been checked out.
good advice...
 
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