Temperature gauge refuses to work


Information and questions on GL1000 Goldwings (1975-1979)
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Workinman
Posts: 10
Joined: Wed Jan 27, 2021 11:42 am
Location: Winston Salem, NC
Motorcycle: 1977 GL1000

Temperature gauge refuses to work

Post by Workinman »



Hey guys. FNG here. I recently did a full restoration on a 77 GL1000 and I have one nagging problem. Actually, I have a few bugs to work out; hesitation off of idle, rattle inside muffler, etc, but the temperature gauge has got me STUMPED. Here’s what I’ve done... first and foremost, I must also say that the gas gauge doesn’t work either, but I believe that to actually be the gauge itself. I’m looking for a decent replacement. I have checked the 7V regulator, 12 volts coming in, 7 leaving. For assurance, I also purchased one of the fine replacement regulators available on the Bay, and it is installed in the bike right now. So, I’ve checked the voltage where the temp gauge hooks up and I have 7 volts there. I’ve grounded the gauge to check it and it buries itself when I ground it. I’ve checked for continuity on the wire going from the gauge to the sender, and I have continuity. So wire is good. I’ve tried hooking up another GL1000 gauge to it and also no luck. I’ve replaced the temperature sending unit TWICE, thinking maybe I got a bad one. Nope. No luck. I do have Teflon tape on the sending unit threads, which from what I understand should not cause a problem, but at this point I’m having my doubts. As you know, changing the temp sending unit is no picnic, so I am trying to avoid a leak and having to do it yet again. I’m hoping someone here has run into this problem before and can tell me how to fix it. I’m at my wits end here. I know the bike is heating up, and I know it’s not overheating, and the fan is working, but I cannot rest until this gauge works. Thanks for your help.
Chris


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dingdong
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Re: Temperature gauge refuses to work

Post by dingdong »

The temp sensor is a single wire sensor. The body of the sensor is part of the circuit. It has to make contct with the (engine/ground) to complete the circuit. Teflon tape is a no no.
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DenverWinger
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Re: Temperature gauge refuses to work

Post by DenverWinger »

dingdong wrote: Sun Feb 07, 2021 9:18 am The temp sensor is a single wire sensor. The body of the sensor is part of the circuit. It has to make contct with the (engine/ground) to complete the circuit. Teflon tape is a no no.
You can confirm this by jumpering the body of the sensor to the engine block, if the gauge magically starts working you know for sure it's the tape.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

Okay... I was “thinking” that the threads would cut through the tape enough to ground it, but I’m gonna try that. It almost HAS to be the problem. The only other thing I could think of was an air bubble inside the block not letting coolant get to the sensor, but I really don’t think that’s it. I’ll report back what I come up with.
Thanks!
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DenverWinger
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Re: Temperature gauge refuses to work

Post by DenverWinger »

Even if the sensor was in a bubble, it would still heat up and indicate on the gauge...
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

Okay, again... if I jump a wire from the body of the sending unit to the engine, I get nothing.
If I jump a wire from the sending unit WIRE to the engine, gauge goes straight to HOT.
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

The bolt holding the housing that the sending unit is screwed into is not grounded to the block. It provides no ground whatsoever. So... I can see why the sending unit would not ground in that housing, tape or no tape, but why won’t it ground when I run a jumper from the outside of the sending unit to a KNOWN working ground? I’m stumped again.
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Maz
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Re: Temperature gauge refuses to work

Post by Maz »

Workinman wrote: Sun Feb 07, 2021 3:06 pm The bolt holding the housing that the sending unit is screwed into is not grounded to the block. It provides no ground whatsoever. So... I can see why the sending unit would not ground in that housing, tape or no tape, but why won’t it ground when I run a jumper from the outside of the sending unit to a KNOWN working ground? I’m stumped again.
Everything points to the sending unit. I know you've replaced it, but there is no other explanation. You could test the sending unit by removing it and test it's resistance with a DVM on the Ohms scale. Heat the sender whilst still connected to the DVM and see if the resistance changes - It should read very high resistance when cold and then reduce as the temperature rises.
Maz
Ironically, Common Sense is the LEAST common of all senses!
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

I’ve tested all three sending units that I have and nothing seems to make much sense. I have also, once again, drained the coolant, slid the carbs back, and removed the sending unit. I just don’t understand why the housing that the sender screws into isn’t grounded at all. I thought that’s how the sending unit worked. There are 7 volts going into the sender and the temperature of the coolant varies the degree to which it is grounded. I must be off in my thinking here. So you guys are saying that I don’t actually want a ground at the housing. No ground= good thing?
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Maz
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Re: Temperature gauge refuses to work

Post by Maz »

Workinman wrote: Mon Feb 08, 2021 11:50 am I’ve tested all three sending units that I have and nothing seems to make much sense. I have also, once again, drained the coolant, slid the carbs back, and removed the sending unit. I just don’t understand why the housing that the sender screws into isn’t grounded at all. I thought that’s how the sending unit worked. There are 7 volts going into the sender and the temperature of the coolant varies the degree to which it is grounded. I must be off in my thinking here. So you guys are saying that I don’t actually want a ground at the housing. No ground= good thing?
The sender body must be grounded for the gauge to work.
Maz
Ironically, Common Sense is the LEAST common of all senses!
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

Progress... with the sending unit out, if I jumper the sender body to a KNOWN working ground, jumper the post of the sender to the wire, and heat up the sender with my mini torch, the gauge works. So how the heck am I going to get the sender to ground when it’s in the block? There is no ground in that area at all. Everything else on the block grounds, but not the housing for the sending unit.
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Maz
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Re: Temperature gauge refuses to work

Post by Maz »

Workinman wrote: Mon Feb 08, 2021 4:00 pm Progress... with the sending unit out, if I jumper the sender body to a KNOWN working ground, jumper the post of the sender to the wire, and heat up the sender with my mini torch, the gauge works. So how the heck am I going to get the sender to ground when it’s in the block? There is no ground in that area at all. Everything else on the block grounds, but not the housing for the sending unit.
The only thing I can think of is that corrosion is isolating the housing from the block, as it SHOULD be grounded to the engine block. If that is the case, it will need dismantling and cleaning, before refitting with new seals.
Maz
Ironically, Common Sense is the LEAST common of all senses!
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DenverWinger
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Re: Temperature gauge refuses to work

Post by DenverWinger »

Corrosion on the bolts that hold the housing to the block? Loosening/cleaning/retightening the bolts may fix this without taking it apart any further.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
Workinman
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Re: Temperature gauge refuses to work

Post by Workinman »

That was it! I loosened the bolt just forward of the temperature sending unit that holds the housing to the block, retightened it, and BINGO. We have a good ground. Put everything back together and the temperature gauge now works as it should. Thanks, guys!
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Joneszy
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Re: Temperature gauge refuses to work

Post by Joneszy »

Learned something today! Good work everyone, a valuable lesson. Will try it on my not working very well gauge on my 83. 7v regulator is OK (ie. fuel gauge good), ground the gauge and it pins to the hot side, changed senders & gauge still doesn't come close to being OK. Not saying it is the cause but one more thing to check out.Thanks for posting that you got your gauge up and running correctly.
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DenverWinger
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1972 CL350 (1980-1988) sold
1978 Suzuki GS550 (1985-2005) sold
1977 GL1000 (2002-2006) sold

Re: Temperature gauge refuses to work

Post by DenverWinger »

Sometimes the best fixes are the simplest! :lol: :lol: :lol:
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
Workinman
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Joined: Wed Jan 27, 2021 11:42 am
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Re: Temperature gauge refuses to work

Post by Workinman »

I also finally got a working fuel gauge, restored it, and got it installed. It’s nice to have all the gauges working as they should!


Workinman
Posts: 10
Joined: Wed Jan 27, 2021 11:42 am
Location: Winston Salem, NC
Motorcycle: 1977 GL1000

Re: Temperature gauge refuses to work

Post by Workinman »

Thought I would throw in a picture of my restored gauges.


I have since replaced the cover over the idiot lights with a NOS one.




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