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Re: gauge silliness [Re: sharpie] #665353
04/09/10 05:40 PM
04/09/10 05:40 PM
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Quote:

Quote:

Motor mounts are rubber and don't ground to the frame. You diffenately need a ground from the block to the body and to the frame.




What I don't understand here is the car runs fine, charges fine, and even has voltage to spare. It's just the gauges.




Actually your headlights are stealing the ground from the gauge grounds when they are on. Look at it this way how does the headlight get it's ground?


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665354
04/09/10 05:46 PM
04/09/10 05:46 PM
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Here is some of the grounds to your headlights. Notice there are several of them. Now, how do these grounds make it back to the [-] side of the battery?

Thru the chassis, then the motor mount bolt, then thru the [-] cable? Or even worst thru the voltmeter negative and/or the temp guage wire and then thru the motor mount bolt? I hope not.

Hopefully you have a cable directly from your [-] side of the battery to the chassis.

Re: gauge silliness [Re: HealthServices] #665355
04/09/10 05:47 PM
04/09/10 05:47 PM
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Do you have a good ground going from the chassis to the [-] battery?

If you do, then you still have to check these and well the other grounds. If you don't you know where your problem is.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665356
04/09/10 05:47 PM
04/09/10 05:47 PM
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sharpie Offline OP
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so the headlights are pretty dim, but still, I'm not sure why the dimmer switch works on the gauge needles. The dimmer switch works for the instrument lamp circuit, not the headlights?

Re: gauge silliness [Re: HealthServices] #665357
04/09/10 05:48 PM
04/09/10 05:48 PM
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sharpie Offline OP
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Quote:

Do you have a good ground going from the chassis to the [-] battery?




probably not.

So what all do you suggest I do?

Re: gauge silliness [Re: sharpie] #665358
04/09/10 05:51 PM
04/09/10 05:51 PM
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If you look at your wiring system you are providing power to everything. But just as important is the ground [-]. Are you providing a good ground to everything? The headlights require more power than just about everything else except for the starter. If you have a ground issue the headlights will tax it.

It is a good thing you only have a two headlight system, with a 4 headlight system if you were to put on the high beam you would either burn something out or the headlights would be even dimmer.

Edit: The other problem with dim headlights is voltage loss going thru the bulkhead, light switch, foot switch, bulkhead again, and finally the headlights. Voltage checks will verify where your losses are.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: sharpie] #665359
04/09/10 05:57 PM
04/09/10 05:57 PM
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Quote:

Quote:

Do you have a good ground going from the chassis to the [-] battery?




probably not.

So what all do you suggest I do?




Take a jumper wire from your wiper ground to the [-] side of the battery and you will most likely notice a night and day difference.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665360
04/09/10 05:59 PM
04/09/10 05:59 PM
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But the proper fix is to put a ground from the battery [-] to the chassis, and a wire from the chassis to the engine block. Make sure the chassis ground for the wiper is good too as well as checking the other grounds.

Notice how most battery grounds have a extra wire? this extra goes to the chassis.




The Ground issue may not be your only problem but it is a good start. Especailly if you know you do not have a engine and chassis ground.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665361
04/09/10 06:38 PM
04/09/10 06:38 PM
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sharpie Offline OP
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Oh wait, in that case, I have a chassis ground (I think it's grounding on the core support). I have a double-wired negative battery cable.

Re: gauge silliness [Re: sharpie] #665362
04/09/10 06:42 PM
04/09/10 06:42 PM
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Quote:

Oh wait, in that case, I have a chassis ground (I think it's grounding on the core support). I have a double-wired negative battery cable.




I would check those grounds then (plus add the engine to chassis ground) and make sure they are well grounded.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665363
04/09/10 06:51 PM
04/09/10 06:51 PM
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Ok check all grounds first, this includes...

  • the headlight grounds in the circuit pictured.
  • engine to chassis ground
  • chassis to battery ground
  • Battery to chassis ground
  • Check the ground you have at the wiper.
  • check path of power to oil pressure guage and to temp guage.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: gauge silliness [Re: HealthServices] #665364
04/09/10 06:57 PM
04/09/10 06:57 PM
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Brian,

I am late to this dance, and Allen & Stumpy are doing a fine job.

I just want to remind you about the fresh paint in your engine compartment. Fresh paint is pretty, but the enemy of good ground contacts. Make sure the to-do list includes undoing the body ground (the one from the negative post of the battery) where it attaches to the core support. Scrape/sand all that pretty paint away to reveal BARE METAL, then reconnect the (also cleaned) wire eye to that spot of bare metal. Find where the headlight wire harness grounds are (probably similar wire eyes) and do the same clean-pretty-paint-to-bare-metal fix.

Re: gauge silliness [Re: HealthServices] #665365
04/09/10 07:23 PM
04/09/10 07:23 PM
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Indiana
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Quote:

If you look at your wiring system you are providing power to everything. But just as important is the ground [-].



In an odd, way, grounds are more important than + voltage. No voltage, no output. If you have voltage but bad grounds, though, that voltage will find a different path to ground, and that's where some wierd stuff can happen.

And FWIW, that blue/black ignition feed shown in an earlier post is an adversary to us all. It connects to almost every ign-hot item, it reaches from the alternator to way up under the dash, yet it has no fusing on it whatsoever. At least my 70 300 didn't. DAMHIK.

Anyone doing extra wiring, wiring repairs, or just loves their car should review that circuit in a FSM and put an inline fuse in it somewhere!

Re: gauge silliness [Re: Fury Fan] #665366
04/13/10 02:50 PM
04/13/10 02:50 PM
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sharpie Offline OP
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I think I have an idea of what's going on now. I mapped my gauges, and if you look at the gauges that aren't responding, you can clearly see there is one circuit that they share with only each other - the grounding circuit.



I'm going to doublecheck the grounds today by making new grounds for both the oil and volts and grounding them close (i.e. not through the bulkhead). I'll update this afternoon.

Last edited by sharpie; 04/13/10 02:51 PM.
Re: gauge silliness [Re: sharpie] #665367
04/14/10 11:43 AM
04/14/10 11:43 AM
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sharpie Offline OP
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Well, you were all correct. I did a simple test yesterday that yielded the best result possible. I took a lead from my multi-meter out of the contraption and attached it to a good body ground. Then, I turned the ignition to "accessories" and put the other end of the lead onto the ground terminal of the oil gauge with the old grounds still hooked up. Both gauges immediately began functioning. So it was obviously ground.

Now, the only place in this circuit that wasn't soldered and shrink-wrapped was the bulkhead connector. In fact, I had fashioned that connector in one of the extra slots in the bulkhead connector, so it probably wasn't even as good as stock. So I cut the two grounds before the connector and put them to a good dash ground. The gauges function perfectly now.

Thanks for your help, everyone!

Re: gauge silliness [Re: sharpie] #665368
04/14/10 11:46 AM
04/14/10 11:46 AM
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Mesa, AZ
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Pat_Whalen Offline
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Sharpie:

What software did you use to recreate your gauge's wiring?

I'm getting tired of a ruler and paper.

Re: gauge silliness [Re: Pat_Whalen] #665369
04/14/10 12:07 PM
04/14/10 12:07 PM
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sharpie Offline OP
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Microsoft Office Visio 2007. I really like it. But there are free ones online, too. Like Gliffy.

Re: gauge silliness [Re: sharpie] #665370
04/14/10 01:36 PM
04/14/10 01:36 PM
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Make sure your other grounds are good. If turning on the headlights affected the guages then the grounds for the headlight circuit should be checked. Use some star washers at the grounds make sure there is no paint in the way. Checking the other grounds would not be a bad idea either.



Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
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