1972 GT750 temp guage goes to max

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TheStone
Posts: 6
Joined: Thu May 27, 2021 2:14 am

1972 GT750 temp guage goes to max

Post by TheStone »

Hey all,

I recently picked up a 72 gt750 and I noticed that the temp guage goes to the max after about 10 minutes of idling (faster if riding). When this happens, the thermostat hasn't even opened yet. I let the bike run for a long while and the hottest it got was 190 F with the IR thermometer. It's also worth noting that the fan never kicked on (it does work when unplugged). I took a resistance reading at the sender and it read 782 ohms when cold, and 42.6 ohms when hot. I've tried to look up what the resistance values are supposed to be with no luck and I'm not really sure where to go from here. Any help is greatly appreciated.

Thank you,
Chris
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BAZ
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Joined: Thu Jun 18, 2009 7:35 pm
Location: Dudley west midlands
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Re: 1972 GT750 temp guage goes to max

Post by BAZ »

Welcome to the Kettle mad house, not me everyone else... But that's not why you called, check the pilot bulb earth on the gauge it is a secondary earth and can cause this problem..guess how I know..cheers Bluesmokebaz.
TheStone
Posts: 6
Joined: Thu May 27, 2021 2:14 am

Re: 1972 GT750 temp guage goes to max

Post by TheStone »

Thank you for the warm welcome, and for the good info. If my memory serves me right, the bulb doesn't light up. I never would have thought to check that.

Much appreciated,
Chris
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BAZ
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Joined: Thu Jun 18, 2009 7:35 pm
Location: Dudley west midlands
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Re: 1972 GT750 temp guage goes to max

Post by BAZ »

Nor me till I did, let us know how you get on.
TheStone
Posts: 6
Joined: Thu May 27, 2021 2:14 am

Re: 1972 GT750 temp guage goes to max

Post by TheStone »

It worked! I moved the wires around, got the bulb the light up and went for a nice long ride. The guage never read above half. I never would have checked the bulb, so thank you very much BAZ!
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: 1972 GT750 temp guage goes to max

Post by teazer »

BAZ wrote: Tue Jun 01, 2021 10:55 pm Welcome to the Kettle mad house, not me everyone else... But that's not why you called, check the pilot bulb earth on the gauge it is a secondary earth and can cause this problem..guess how I know..cheers Bluesmokebaz.
Baz,
That is great piece of information. Maybe we could make that into a sticky so it's easy fr other "overheating" 750 owners can find it.
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