My car was running a bit warmer than usual today although as long as I was moving it still seemed in a "safe" zone. When i got home I let it idle and watched and saw the fan flicking on for a second here and there but not consistently. i put the wires together and the fan runs. The thermal switch is only about a year old but can it be already failing? Could this be a sign of a failing relay or perhaps something else?
Thanks
Thermal switch failing or maybe relay?
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georgeramos
- Posts: 1359
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- Your car is a: 1971 124 Spider 1608
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courtenay
- Patron 2020
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- Your car is a: 1980 Spider 2000
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Re: Thermal switch failing or maybe relay?
The thermal switch might be fine, but your temperature sensor might be the culprit. Get one of those infrared temperature sensors and take readings on your radiator and block to see how the temps look.
Bruce Shearer
'80 Spider Fi
'10 Volvo XC70
'06 GMC 1 Ton PU
'72 Spider a long, long time ago
'80 Spider Fi
'10 Volvo XC70
'06 GMC 1 Ton PU
'72 Spider a long, long time ago
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focodave
- Patron 2018
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- Your car is a: 1980 Spider 2000 F.I.
- Location: Fort Collins, CO
Re: Thermal switch failing or maybe relay?
The radiator fan switch is easy enough to test.
An ohmmeter is what I would use.
I believe you have an early car, so your switch should have two spade terminals that are easy to access.
The most accurate way to test it would be to remove it from the radiator and put the proper end of it in a small pot of hot water while monitoring the switch closing/opening at the two spade terminals with the ohmmeter.
You can control the temp if you use a small kitchen pot on a stove and if you have a good thermometer handy.
Just keep the ohmmeter hooked up to it and observe the switch closing when it gets hot and open when you remove the switch from the hot water.
Or -- you could test it in-situ, with the car running but you will have to get down in that tight space with your ohmmeter leads to connect to the switch terminals (or access it from under the front of the car) -- and you won't have control over the temperature very well if you want to observe it for some period of time.
Either way, it is a simple thermal-activated switch that is supposed to close when it gets hot, and open when it gets cool.
The fact that the fan ran when you shorted the two switch wires could be an indication of a bad switch -- or -- that the radiator is plugged (or something else is wrong with coolant flow) and the switch is not sensing hot water near the bottom of the radiator.
Or it could be the relay or a faulty wire or connection somewhere in the circuit.
An ohmmeter is what I would use.
I believe you have an early car, so your switch should have two spade terminals that are easy to access.
The most accurate way to test it would be to remove it from the radiator and put the proper end of it in a small pot of hot water while monitoring the switch closing/opening at the two spade terminals with the ohmmeter.
You can control the temp if you use a small kitchen pot on a stove and if you have a good thermometer handy.
Just keep the ohmmeter hooked up to it and observe the switch closing when it gets hot and open when you remove the switch from the hot water.
Or -- you could test it in-situ, with the car running but you will have to get down in that tight space with your ohmmeter leads to connect to the switch terminals (or access it from under the front of the car) -- and you won't have control over the temperature very well if you want to observe it for some period of time.
Either way, it is a simple thermal-activated switch that is supposed to close when it gets hot, and open when it gets cool.
The fact that the fan ran when you shorted the two switch wires could be an indication of a bad switch -- or -- that the radiator is plugged (or something else is wrong with coolant flow) and the switch is not sensing hot water near the bottom of the radiator.
Or it could be the relay or a faulty wire or connection somewhere in the circuit.
1980 Spider 2000 F.I. (my hobby)
1970 MGB GT (my other hobby)
2008 Ford Expedition (daily driver)
2019 Harley-Davidson Electra Glide Standard
2019 Harley-Davidson Iron 883 Sportster
1970 MGB GT (my other hobby)
2008 Ford Expedition (daily driver)
2019 Harley-Davidson Electra Glide Standard
2019 Harley-Davidson Iron 883 Sportster
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georgeramos
- Posts: 1359
- Joined: Wed Nov 02, 2011 11:11 am
- Your car is a: 1971 124 Spider 1608
Re: Thermal switch failing or maybe relay?
Turned out my thermostat failed. This original post must have been the first time i realized it...
Purchased a new one along with thermal switch (from AutoRicambi) so Im looking forward to rebuilding the system with these low temp parts to see if it lasts longer...I rebuilt the system including recoring the rad, water pump, thermostat, thermal switch, hoses etc about a year and a half ago BUT I did not clean up the wiring connections which were pretty nasty looking so that was likely the culprit of the system falling apart on me again.
moral of the story: clean up the wiring
Purchased a new one along with thermal switch (from AutoRicambi) so Im looking forward to rebuilding the system with these low temp parts to see if it lasts longer...I rebuilt the system including recoring the rad, water pump, thermostat, thermal switch, hoses etc about a year and a half ago BUT I did not clean up the wiring connections which were pretty nasty looking so that was likely the culprit of the system falling apart on me again.
moral of the story: clean up the wiring