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no gauges, 7V regulator is good

Posted: Thu Feb 13, 2020 10:30 am
by old_smokey
Hi fellow 'wingers.

I've got a problem with some of my gauges, and it's not the 7V regulator.

I have a new-to-me 1975 GL1000. Bought it from the original owner, who had it parked out in a shed for several decades. I've already done a the basics - new timing belts, fluid change, valves, electronic ignition even, filters etc. I've taken it on a few rides and it's a beauty. But my temp and gas gauges both read zero.

I've read at least a few dozen threads on the issue. I tested my 7V regulator and it appears good - 12V in, 7V out, and ground. I traced the wire up to the gauge and tested there - 7V input as well. I grounded the wire that runs down to the temp sensor and the gauge did not move at all. The other dash lights dimmed slightly, indicating a load was being drawn. Ignition was turned on, but bike was not running.

Not sure what to make of this. Seems i have good power to the gauge, and by grounding the wire to the sensor I should have it isolated to the gauge itself. Is there any other test I can try? Is my temp sensor itself fried?

My fuel gauge also does not work. I haven't tried checking for power and shorting the wires at the sender yet - that is tonight's job.

I have confirmed the fan works, and it does come on after idling for a while.

Re: no gauges, 7V regulator is good

Posted: Fri Feb 14, 2020 10:08 am
by old_smokey
Success last night. I got both gauges working.

First I removed the seat to inspect the fuel sender. Ah ha...there's the problem. One of the sender wires is disconnected! I cleaned both connectors and reattached. Still no activity on the gauge though. hmm...

Checked for good power and ground, and had both at the harness. Measured resistance of the sender and it registered around 80ohms. That's standard for an empty tank.

Wait a second...empty tank....haha!! Popped the fuel cap open and sure enough, the tank was nearly completely empty. So I moved the float up and down by hand and presto the fuel gauge responded. The needle moves quite slow, but I hear that's pretty typical.

Next up, temp gauge. I tested a healthy 7V at the gauge, but found large resistance in the wire running down to the sender. Time to trace and inspect. WOW is that sender in an inconvenient location. I was able to pull the connector off with some very long pliers, and found it was heavily corroded and green. Ah hah! Gave the connection a thorough cleaning, then grounded it out with the key on. Eureka! The temp gauge slowly climbed to max.

One thing I want to confirm - does the temp gauge have any way of turning on the fan? Or is that entirely controlled by the fan switch? The fan never turned on when the gauge climbed, but if I'm looking at this correctly, they are independent circuits.

Re: no gauges, 7V regulator is good

Posted: Fri Feb 14, 2020 12:45 pm
by froche
I believe that the Temp gauge and the fan switch are different circuits. My 1200 had a bad fan and I wired in a "parade" switch to allow me to switch it on and off. During that time the temp gauge worked fine. Eventually i replaced the fan switch and it all worked fine.

To wire up a parade switch you simply use an SPST switch (on and off toggle for example) and use it to connect the wires that go to the fan switch. Each wire attached to the switch is connected to one of the fan switch (in parallel). That way you can control when the switch is turned on.

I used a switch from a car (GEO METRO 1992-1994) purchased from Rockauto for about 16.00, also purchased the correct fitting for the wiring. The switch at Autozone is 32 to 49 dollars. Correct fan switch connector Complete kit with extra terminals MT-2S-8 8.00. Apparently it is a Sumitomo MT Sealed Series OEM P/N: 6189-0033 the 8.00 included extra terminals in case I blew it and shipping!

There is a small difference in temperature it starts the fan at but it is about 10 degrees, not a problem.