guages

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guages

Postby skizer » Tue Dec 29, 2009 7:04 pm

I have a75 monza that I am getting close to getting back together. I got the motor fired up the other day and none of the guages, amp, tach, temp or fuel are working. I checked all the fuses, regrounded the two wires coming from the harness. I know they worked, at least the tach when it was in the other car. I am not very good wth electrical issues, Any suggestions
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Re: guages

Postby cjbiagi » Tue Dec 29, 2009 7:36 pm

The fact that none of them work indicate it something common to all. Most gauges need 3 signals to work, 12volts, a ground and the sender signal. Do you have 12 volts to the gauges? It probably either the 12 volt line or the ground. Since it seems you checked the ground I would break out a volt meter and make some simple checks. There is a fuse for the gauges, I would check there first. Looks like a pink wire supplies the 12 volts to the ignition switch and then up to the dash. Get a meter (or at least a 12 volt pigtail and bulb) and check for voltage at both sides of the fuse. Let us know what you get there......
Clyde.........75 Monza 2+2
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Re: guages

Postby skizer » Tue Dec 29, 2009 10:25 pm

thanks clyde i will try to check that soon
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Re: guages

Postby skizer » Thu Dec 31, 2009 6:53 pm

well i checked the power at the fuse box and all was ok, 12 volts. i checked the power at the plug for the tach and fuel and I had twelve volts there too so I guess my problem is in the signal
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1975 Chevrolet Monza Hatchback

Re: guages

Postby cjbiagi » Thu Dec 31, 2009 6:57 pm

Well it could still be the ground. You said several gauges weren't working, so I doubt that it is the signal wire. Check for voltage between a known good 12 volt source and the ground at the gauge to verify that you have a good ground all the way to the gauge. The 12 volts go through the ignition switch too so check that big connector on the steering column. Are you measuring 12 volts right at the back of the gauges?
Last edited by cjbiagi on Thu Dec 31, 2009 7:15 pm, edited 1 time in total.
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Re: guages

Postby 72 SS PNL » Thu Dec 31, 2009 7:05 pm

connect the test light or volt gauge pos and neg

then use a ohm meter to check the resistance on the ground from the tach ground to a chassis post under the hood or direct to the battery
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Re: guages

Postby skizer » Thu Dec 31, 2009 7:58 pm

when i checked the power at the plug for the gauge i used the ground for the plug also and it measured 12 volts After further examination, the fuel guage might in fact be working. I do not see the tach on the wiring diagram, whn I unplugged it from the back of the tach, the wire was a dark brown for the lead. the one under the hood is a tan and white i think. it is connected to som kind of suppressor that is bolted to the fire wall. does this sound like the right wire for the tach
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1975 Chevrolet Monza Hatchback

Re: guages

Postby cjbiagi » Thu Dec 31, 2009 9:51 pm

Yes, the sender wire is brown and it connect to the distributor and then connects to a filter capacitor on the intake manifold.
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