[Xtreme70SS396]

If you haven't read my previous posts, converted from idiot lights to gauges on my '70SS. Used Jim Endrud's wiring instructions, but my wiring seems to have been messed with before me.

Had the ammeter wired wrong, working on that (Thanks, Elree). My main power feed from the battery may be corrected by this.

My clock, temp gauge, and fuel are not functioning:
1. I don't think they are getting any power. Clock is a new quartz conversion and hasn't budged.

2. Temp gauge is pegged all the way to the right, and after reading many posts here, I tested - there is a short to ground somewhere, I ran a continuity tester to the sending unit (peg is not grounded) and then tested the sending wire, and it is grounded somewhere.

3. Temp gauge has the orange ceramic resistor thing, going from the top to the bottom of the posts on the gauge. However, it is on TOP of the circuit board, I don't know if it matters, but I read in on of the posts the pcb is supposed to go on top of it, not the other way around.

4. Fuel gauge (pegged to the left) also has ceramic resistor, also on top of the pcb.

5. PCB is new.

Many thanks in advance.

 

[John_Muha]

On your shorted temp wire:
The idiot light car tests the GEN bulb by shorting the sender wire to ground. This is done by the ignition switch. It's normally only done as you start the car.
On the ignition switch, there was 2 dark green wires that are tied together. Unplug that connector from the ignition switch and see if the short to ground goes away.

 

[Xtreme70SS396]

How hard is it to get to the wire on the switch? Is there an under-dash or behind-dash spot to intercept it? FYI, I wired the temp sending wire directly into the cluster connector behind the gauges.

Also, the ground is happening 100% of the time, whether the ignition switch is on or off.

[This message has been edited by Xtreme70SS396 (edited 04-18-2002).]

 

[John_Muha]

Is the green wire disconnected from the meter as you take your measurements? If it is not it could be giving you a false reading.
The ignition switch is on the top of the column. Should be able to reach under there and pull off the connector with the 2 green wires.

I understand that it's not suppose to go to ground with the switch off. I was guessing at a likely area that might be the problem. Since they do go to ground in the start position, guessing that maybe the switch might be the place where they are now shorted.

 

[Xtreme70SS396]

I'll check that out, John, thanks.

 

[Steve S]

Install the resistors under the pcb. The resistors should be installed on the gauges with nuts, then the pcb then another nut to secrure the pcb and make connection to the gauge. There are spacers that also mount on the gauges other terminals so that the pcb is flat across the gauge connections. They will probably work the way you have them as long as you have a nut for the pcb and the resistor. If you mounted the pcb then the resistor and only one nut on top, the pcb is not making connection to the gauge. The case on these gauges is grounded, so if you have any nuts directly on the gauge terminal with nothing underneath you are grounding that terminal.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
My 70SS

 

[Xtreme70SS396]

Update- I checked the pcb last night:
1. I moved the ceramic resistor to on top of the pcb.

2. There is NO pcb connection to the ceramic resistor, it didn't matter whether it went on top or on the bottom - the connection points for the pcb are only the left and right side terminals of the temp gauge, nothing on top/bottom. ?

From everything I've been reading here and been told, this is supposed to connect to the pcb. (Yes, it's a gauge cluster pcb)

3. I left the right side (while facing the gauge) terminal off the pcb for now.

4. I checked for ground again from the sender wire - it is no longer grounded. (Guage remains to far right, but I don't have any power to it yet anyway) I will connect right side terminal and retest ground again.

 

[Steve S]

I was going off of memory (which is the first thing to go and I can't remember the second) and I may be wrong. I will have to look at mine. I should know better by now to offer advice without checking first. You might be better off removing the cluster and bench testing. I can email a procedure for each gauge. All you need is a 12v source (battery, charger, power supply) and some wire.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
My 70SS

 

[Elree Colby]

The temp gauge- During factory assembly the resistor was installed before the PCB. The top and bottom posts don’t have a connection to the PCB. The bottom post needs to be grounded. It should make contact with the metal back of the inst cluster that ultimately is grounded to the body. Check for continuity between the bottom post and body metal. The cluster back should have a black ground wire under one of the screws. You should read about 62-64 ohms between the top post and ground. This verifies good contact with the resistor. The cluster connector needs to be disconnected during the above measurements. I’m sure you did but I gotta ask. You did replace the temp switch (in the head) with a temp sensor, right?

The clock- gets power from the top left fuse in the fuse block. CLK LTR_____CTSY. It grounds to the cluster back. So if you don’t have a good cluster ground it won’t work.

The fuel gauge- The bottom post also needs to be grounded.

Check for a cluster ground. If it’s good post that information and someone will provide additional help.


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TC member 368
My ElCamino 1
My ElCamino 2
My ElCamino 3

[This message has been edited by Elree Colby (edited 04-19-2002).]

 

[Xtreme70SS396]

Thanks, guys.

Steve, that procedure might come in handy, even if I don't use it now - my email is [email protected].

Elree, I did replace the temp sender with the gauge unit. I will check for ground and resistance this weekend for the temp and fuel gauges. I already know the cluster is grounded, but of course I will check again.
I have the power for the clock connected at the clock, but need to verify that the source wire ends up at the panel, and isn't just dangling somewhere. FYI, I'll be pulling the amp gauge I fried this weekend also. Thanks!!

 

[chevyjim]

Do all of the bulbs for nightime illumination light up when the light switch is pulled out or just the ones in the speedometer / clock area of the dash? This is a good way to check for problems associated with gauges. If they don't all light and the bulbs are good you could have ground problems on the circuit board. I have had hairline cracks on the circuit board, especially where the bulbs contact the board. If the crack is before the 1/4 head screws that ground the smaller gauge metal housings to the board, the gauges can act crazy. Also check for corrosion under these screws and make sure they are tight and not stripped out. I think it's the only way the smaller gauges get a chassis ground. I've had the same problems you are having and it was actually a combination of all these things. It's been so long I just can't remember. I hope this helps !

[This message has been edited by chevyjim (edited 04-21-2002).]

 

[Xtreme70SS396]

chevyjim, thanks for you post. All the lights do work - I am continuing to learn and work on them now.

My problems seem to be a combination of things, I think thanks to help here I have nailed them, but won't know for sure till I fire it up again. Anyway, my problem seems to be the way I had the ceramic resistors connected for the fuel gauge (not contacting circuit board) and bad ground on the both temp and fuel gauges.

The ground for these gauges is now a separate wire I just added, but otherwise you would need to first have a nut connecting the grounding terminals (bottom on both gauges) to the metal backing plate. I did not do that, and the gauges were not really grounded - the pcb was actually insulating them from ground in my case. (This as best as I can figure it.)

Re-reading all the related posts on these gauges and double-checking mine really taught me quite a bit on this, and I suck at the electrical stuff.