Keep blowing the "IGN" fuse!!!

[Da Flash]

Ok, I reconnected the tach, oil/temp, amp/fuel and the hazard switch. If I disconnect the fuel/amp connector and check for resistance between the green wire (at the fusebox) and the Y/R wire at the connector, I get a reading of 001. If I reconnect the fuel/amp and disconnect the oil/temp I get a reading of 001 at one of the 2 yellow wires (the other 2 are Blk and W/B). If I reconnect the oil/temp and disconnect the hazard switch, I get a reading of 001 at the G wire and readings of 033 at the G/B and G/R wires. If I reconnect the hazard and disconnect the tach I get readings of 001 at the R/L wire that transitions to a Y/R wire on the back of the tach. I also get a reading of 001 when I check the oil/temp, amp/fuel or tach Blk wire to the metal dash frame.

I was thinking maybe a bad gauge but, if that were it, wouldn't unplugging the bad gauge give me infinite resistance between it and ground??

All readings were done with the multimeter set to 2K.

I hope that this is what you were asking for if not, please feel free to elaborate!!

Thanks!!

[Zed Head]

What brand of meter are you using? 001 might just mean "out of range".

You might consider a test light in place of the fuse. Disconnect everything, insert a light in place of the fuse, either built yourself with alligator clips and wire, or one from the parts store, apply power to the system, then reconnect each item. The shorted component or wire will cause the test light to glow the brightest, but the light bulb will protect the circuit from too much current.

I didn't follow out the wiring diagrams but it could be something as simple as a shorted gauge bulb, or bulb socket. The little BA9 bulbs have their electrodes in close proximity.

[Da Flash]

It's a Mastech meter and I thought that 001 meant very little to no resistance. I would try the test light but I already have the dash out and have found it easier to disconnect and reconnect things with the dash out. Trying to get to the tach connectors is a major PITA with the defrosting ducting in the way. I guess I could just reinstall the dash without the ducting for testing purposes. I've gotten pretty good at installing and removing the dash!!

Thanks!!

Edited February 24, 2014 by Da Flash

[Zed Head]

You could also use a battery and alligator clips with a light at the power wires in the connector. I do it with gauges on the bench.

I don't think it will hurt your meter to turn the dial to other resistance ranges while it's connected. Most meters are able to give an actual number, even no resistance has some resistance.

On the meter usage - a typical meter test is to touch the two probes together to check the battery and probe connections to the meter. If everything is right you should the very, very low reading or zero, for no resistance. Then you'll know for sure what no to low resistance looks like on the meter.

Edited February 24, 2014 by Zed Head

[beermanpete]

Ok, I reconnected the tach, oil/temp, amp/fuel and the hazard switch. If I disconnect the fuel/amp connector and check for resistance between the green wire (at the fusebox) and the Y/R wire at the connector, I get a reading of 001. If I reconnect the fuel/amp and disconnect the oil/temp I get a reading of 001 at one of the 2 yellow wires (the other 2 are Blk and W/B). If I reconnect the oil/temp and disconnect the hazard switch, I get a reading of 001 at the G wire and readings of 033 at the G/B and G/R wires. If I reconnect the hazard and disconnect the tach I get readings of 001 at the R/L wire that transitions to a Y/R wire on the back of the tach. I also get a reading of 001 when I check the oil/temp, amp/fuel or tach Blk wire to the metal dash frame.

I was thinking maybe a bad gauge but, if that were it, wouldn't unplugging the bad gauge give me infinite resistance between it and ground??

All readings were done with the multimeter set to 2K.

I hope that this is what you were asking for if not, please feel free to elaborate!!

Thanks!!

Ok, I get the feeling you are measuring the resistance of the wire, from the fuse to the meter, on the positive side of the circuit. If this is the case your readings are fine but you are not looking in the right place. Try measuring from the green wire at the fuse to ground, which is the black wires at the meters. This should measure higher, as Steve mentioned earlier. The meters normally only draw a few milliamps, perhaps about 1oo mA at full scale, so the circuit resistance will be in the 120 ohm range.

If you are measuring from the green wire to the black wire and getting "001" you have a short somewhere. In this case it is likely in the wiring rather the meters themselves. To test the meters measure each from the Y/R to the black or the meter case. Test wiring with all the meters disconnected by measure from the green wire at the fuse to the black wire in the connector where the meters plug in. This should measure open (infinity).

[Da Flash]

Ok, I get the feeling you are measuring the resistance of the wire, from the fuse to the meter, on the positive side of the circuit. If this is the case your readings are fine but you are not looking in the right place. Try measuring from the green wire at the fuse to ground, which is the black wires at the meters. This should measure higher, as Steve mentioned earlier. The meters normally only draw a few milliamps, perhaps about 1oo mA at full scale, so the circuit resistance will be in the 120 ohm range.

If you are measuring from the green wire to the black wire and getting "001" you have a short somewhere. In this case it is likely in the wiring rather the meters themselves. To test the meters measure each from the Y/R to the black or the meter case. Test wiring with all the meters disconnected by measure from the green wire at the fuse to the black wire in the connector where the meters plug in. This should measure open (infinity).

Ok, you're right I was testing the positive wiring. When I test the green wire to the black wire on the oil/temp or amp/fuel I get a reading of .057. When I test the black wire to the tach I get .030. There are no black wires on the hazard switch wiring but I do get .033 when I test the G/B and G/R wires.

As stated before, if I disconnect all 3 gauges, the resistance goes away. The hazard has no effect on the resistance.

Thanks!!

[beermanpete]

Ok, you're right I was testing the positive wiring. When I test the green wire to the black wire on the oil/temp or amp/fuel I get a reading of .057. When I test the black wire to the tach I get .030. There are no black wires on the hazard switch wiring but I do get .033 when I test the G/B and G/R wires.

As stated before, if I disconnect all 3 gauges, the resistance goes away. The hazard has no effect on the resistance.

Thanks!!

You said you are using the 2K range so .057 should be 57 ohms. With 12 volt the current draw would be about 0.2 amps. Not exactly what I reported it would be but not a fuse blowing short either. With this in mind it seems the meters are ok.

[Da Flash]

Any suggestions on what I should test next??

[beermanpete]

Check the other branches on this circuit. Turn signals (via the hazard switch, green in-out to flasher), charging system (black/white wire to regulator), choke lamp (red wire to switch on the choke control).

[Zed Head]

You do know what you're looking for, right? The wire or component that has zero or very low resistance. Just leave your meter connected to the green and black wires and connect and disconnect things until you find the thing that causes very low resistance. That low resistance is what allows the current to flow that overheats and blows the fuse.

[Da Flash]

You do know what you're looking for, right? The wire or component that has zero or very low resistance. Just leave your meter connected to the green and black wires and connect and disconnect things until you find the thing that causes very low resistance. That low resistance is what allows the current to flow that overheats and blows the fuse.

Kinda, sorta, not really. I think that I'm looking for the device that when disconnected gives me a reading of 1. (meaning infinite resistance or higher than the range that I have set). The problem that I'm having is that the only thing that will produce an infinite resistance to ground is when all 3 gauges are unplugged (oil/temp, amp/fuel and tach). If I plug in any of the 3, I get readings of .456 or .030. I know that this isn't a reading of .001 but it's close making me believe that it is a least part of the problem. I'll check out the wiring for the other devices that BMP mentioned and see if I can find something new.

Thanks for your input!!

[Da Flash]

You said you are using the 2K range so .057 should be 57 ohms. With 12 volt the current draw would be about 0.2 amps. Not exactly what I reported it would be but not a fuse blowing short either. With this in mind it seems the meters are ok.

It's been a while since I've had time to work on this. I'm not so sure it's not the gauges. Following the advice given in this thread, the only things that I can disconnect and get rid of the resistance are the gauges. It has something to do with the gauges being installed/grounded to the dash. I can connect all 3 gauges and get no resistance as long as they're not grounded. I also find it odd that with the gauges installed in the dash, I can get resistance to ground reading on all the pins at the connectors for the 3 gauges (oil/temp, amp/fuel, and tach) I realize that the black wire is a ground but, I find it hard to believe that all the wires go to ground!!