Temperature Gauge Goes Straight Past Hot


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josh.anderson
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Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »



Hello. I am hoping someone can help me with my 1975 GL1000. Within 5-10 minutes of starting the bike the temperature gauge moves straight past the H on the right. This is what I know and have tried so far; I tried a working tach/temp. gauge from a different GL1000. I replaced the 7-volt auxiliary regulator. I replaced the fan control switch AND the water temp. sending unit. Any ideas on what I should try next? Thank you.


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Re: Temperature Gauge Goes Straight Past Hot

Post by winguyjo »

since you didn't specify whether you had or not ... check coolant level. if that's ok i would go straight to replacing the thermostat.
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

Sorry about that. Coolant level is fine. I'll replace the thermostat. Thank you.
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Re: Temperature Gauge Goes Straight Past Hot

Post by AZgl1800 »

do NOT buy an aftermarket thermostat....

OEM fits better.

I bought a Stant for my ST1100 and it would not fit the housing, took it back to the store.

Ordered up a Honda stat.

IF,
when you remove the stat, and it looks like it is all corroded up, put it in something to remove the junk, it just might clean up and work correctly.

you can test that by putting it in a pan of water and seeing if it is fully open before the water boils.
~John

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josh.anderson
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

Ok, I removed the thermostat and tested it per the instructions from the shop manual. It did open before boiling (not sure as to its full extent), so it appears to be working. But, I may go ahead and replace it since it is already out and I'm running out of options as to the cause.
Recommendations or ideas?? Thank you.
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Re: Temperature Gauge Goes Straight Past Hot

Post by dingdong »

Is your fan coming on? You didn't say.
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

No, the fan does not come on. It does work, but it will not automatically turn on when it is supposed to.
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AZgl1800
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Re: Temperature Gauge Goes Straight Past Hot

Post by AZgl1800 »

josh.anderson wrote: Fri Jul 10, 2020 9:47 pm No, the fan does not come on. It does work, but it will not automatically turn on when it is supposed to.
the fan is controlled by a Thermal Switch, and if it does not cycle on, it is very doubtful that the bike is overheating.

Do you have access to an IR Temperature gun?
cheap at harbor freight.

use it to check temps on hoses, radiator, tires and wheel hubs.
Never leave home without one.
~John

'02 GL1800
2009 Piaggio MP3 250cc
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

The thermostat was not the problem Any other suggestions as to why the temp. gauge goes straight past H within minutes of the bike idling? Thanks.
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Re: Temperature Gauge Goes Straight Past Hot

Post by DenverWinger »

Not wired correctly into the 7v regulator and getting 12v instead? Can't be getting that hot just idling 5 mins. And if it was that hot you'd have coolant out the overflow and steam....
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Re: Temperature Gauge Goes Straight Past Hot

Post by cfairweather »

It is a common problem for the 7 volt regulator to cause this issue and your replacement may also be bad. I would check the output voltage of the regulator with a volt meter. Do this check when the gauge is normal and also when is shoots up. If your fuel gauge is abnormal too, your regulator is probably bad. Both get power from the 7 volt regulator.
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Re: Temperature Gauge Goes Straight Past Hot

Post by WingAdmin »

Keep in mind that there are two thermal sensors. One is a switch which activates the fan when the temperature gets warm, and the other is a sensor that controls the reading on the temperature gauge.

Start the bike with the radiator cap removed, and rev the engine a few times, to make sure that you see the level of coolant in the radiator neck change. This will tell you that the water pump is functioning.

If that checks OK, the next thing I would look at is the 7 volt regulator.
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

I started the bike with the radiator cap removed and revved the engine, but the fluid level did not fluctuate at all. So, I'm assuming that indicates that the water pump needs replaced? Thank you.
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Re: Temperature Gauge Goes Straight Past Hot

Post by WingAdmin »

josh.anderson wrote: Tue Jul 14, 2020 5:54 pm I started the bike with the radiator cap removed and revved the engine, but the fluid level did not fluctuate at all. So, I'm assuming that indicates that the water pump needs replaced? Thank you.
It's possible. The other option is that the thermostat is stuck and clogged, not allowing any coolant to get to the radiator.

Here's how it works. The water pump takes coolant and pumps it upward into the engine, around the cylinders, where it picks up heat. It then exits the top of the engine through the coolant pipes, which I colored in yellow. It then goes to the thermostat, which I colored green. If the coolant is still relatively cool, the thermostat is closed, which means it directs the coolant directly back to the water pump (blue arrows). If the coolant is hot enough, the thermostat opens up, directing the coolant to the radiator (red arrows). The radiator cools the coolant before it gets returned back to the water pump.

If the thermostat is stuck, and never opening up, it could be never sending coolant to the radiator. If the water pump is not operating, obviously you won't have any cooling going on at all.

I would check the temperature of the collector tubes (yellow) and the radiator hose (red) after the bike has been running for a few minutes. An infrared thermometer is best for this. If the yellow tubes are 85C (185F) and the radiator hose (red) is still cold, then your thermostat is not opening. If your yellow tubes are not at least 80C (185F) after a few minutes of running, then it's likely that coolant is not being circulated, meaning the water pump is not operating.

However...the fact that the fan is not coming on and yet the temperature gauge is pegging, says to me that the cooling system is operating properly, and it is the gauge that is wrong - which would indicate a failed 7 volt regulator, or a shorted wire in between the temperature gauge and the temperature sensor.

GL1000 Coolant System
GL1000 Coolant System

josh.anderson
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

Thank you WingAdmin (and everyone else) for the information that you have provided.

I let the bike idle for about 10 minutes and checked the coolant pipes (in yellow) and the radiator hoses with an IR thermometer. The coolant pipes were reading in the mid-90's (C) and the radiator hose had risen to about 45 (C) when I turned it off.

Here is what I have done so far;
I've installed a working tach/temp. gauge, a working thermostat, a new temp.sensor, a new thermostatic switch, and a new 7-volt regulator that is putting out 7-volts. I believe that I have it narrowed down to either a faulty water pump or a shorted wire in between the temp. sensor and the temp. gauge. Does this sound correct?
Thank you.
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Re: Temperature Gauge Goes Straight Past Hot

Post by WingAdmin »

josh.anderson wrote: Wed Jul 15, 2020 3:21 pm Thank you WingAdmin (and everyone else) for the information that you have provided.

I let the bike idle for about 10 minutes and checked the coolant pipes (in yellow) and the radiator hoses with an IR thermometer. The coolant pipes were reading in the mid-90's (C) and the radiator hose had risen to about 45 (C) when I turned it off.

Here is what I have done so far;
I've installed a working tach/temp. gauge, a working thermostat, a new temp.sensor, a new thermostatic switch, and a new 7-volt regulator that is putting out 7-volts. I believe that I have it narrowed down to either a faulty water pump or a shorted wire in between the temp. sensor and the temp. gauge. Does this sound correct?
Thank you.
When you did that test (when the radiator hose was at 45C), was the temp gauge showing full scale at that point?
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

It was not pegged to the right (H), but it was much closer to the "H" than was was to the middle. According to the photo in my manual, the engine temp. would have been around 110-120 degrees C.
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

I think I figured it out. I'm going to take a short ride and then I'll let you know. Thanks again.
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Re: Temperature Gauge Goes Straight Past Hot

Post by josh.anderson »

It was the 7-volt regulator. I want to thank those of you who had taken the time to help.
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Re: Temperature Gauge Goes Straight Past Hot

Post by WingAdmin »

josh.anderson wrote: Wed Jul 15, 2020 5:43 pm It was the 7-volt regulator. I want to thank those of you who had taken the time to help.
Glad you got it working again!


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