I think my radiator fan switch (if that's the right word - here in France they call it a "thermo-switch") has failed, because the fan no longer switches on but it does work when connected directly to the battery.
My switch has three black wires, but only two are connected. The third wire has always just been coiled up unconnected. There is nothing connected to the earth tab on the copper washer between switch and radiator, but in the days when the switch still worked I once tried the mysterious third wire on this tab and the result was that the fan worked continuously when the ignition was on (the Italian Connection..?).
A mechanic told me that I could test the switch by checking for current with the ignition switched on, but I'm not sure what he meant. If I connect a test light to the switch, presumably I should see current from at least one of the terminals when the ignition is on. If not, can I assume that the switch is knackered?
If the switch needs to replaced, which model should I be looking for? This may sound stupid, but since I only have two wires connected, shouldn't I have the 2 wire switch instead of the 3 wire model I have on the car at the moment? Both are available.
The other possible fault in this circuit is in the relay. Do these things fail, and is there a simple way to test?
Presumably it's just an ordinary 4-terminal 30A relay?
Any advice for the electrically ignorant would be greatly appreciated.
Andy
radiator fan switch
-
Hamish
Re: radiator fan switch
Andy,
Three black wires?!! The wiring to the overheat fan should consist of two fairly thick wires, one blue and one black. The thermo switch should have two wires, one white & black and one black. The black wire goes to an earth point beneath the right hand side headlights (they are also earthed here) and the white and black links into the loom close to the connections for the overheat fan. The temperature switches themselves are actually located in the cylinder head in between the spark plugs.
I would imagine that you should try and trace the wiring to the switch (presumably this is at the front of the radiator unless it's an early model?) for faults first, these switches rarely fail in my experience but the wiring does!
You should be able to swap relays without trouble to test the circuit - these also rarely fail unless there's something far wrong with the electrics!
I'd check the wiring first especially all earths and connections and see how you go from there.
Hamish
Three black wires?!! The wiring to the overheat fan should consist of two fairly thick wires, one blue and one black. The thermo switch should have two wires, one white & black and one black. The black wire goes to an earth point beneath the right hand side headlights (they are also earthed here) and the white and black links into the loom close to the connections for the overheat fan. The temperature switches themselves are actually located in the cylinder head in between the spark plugs.
I would imagine that you should try and trace the wiring to the switch (presumably this is at the front of the radiator unless it's an early model?) for faults first, these switches rarely fail in my experience but the wiring does!
You should be able to swap relays without trouble to test the circuit - these also rarely fail unless there's something far wrong with the electrics!
I'd check the wiring first especially all earths and connections and see how you go from there.
Hamish
-
lancisti mikele
Re: radiator fan switch
take a new thermo-switch and the problem
is gone.i had it
happens in the
garage, now al is okay
mikele
is gone.i had it
happens in the
garage, now al is okay
mikele
-
alan cooper
Re: radiator fan switch
I would agree that fan swithes rarely fail completely but what they do suffer from is a gradual degrading of performance over the years resulting in the fan cutting in later and later. I am sure all Beta owners are well aware of the risks of overheating in these cars and I would take the view that you cannot be too careful. It is well worth rigging up a manual override switch (you can use one of the spare ones on the dash) connected to the relay and use it to switch on the fan as soon as you hit a traffic jam. this way you do not risk a build up of heat. If the fan doesn't come on when you use the switch you then know that the relay has gone and can take action before all is lost!
-
Randy Adams
Re: radiator fan switch
Hi Andy:
I understand that you have an early model (1974 vintage) from another post.
For what it's worth, my later 1981 USA fuel injected model uses a thermo switch with only two wires. Since Hamish reports the same thing, I recommend that you obtain a two wire variant.
I join Mikele in reporting a thermo switch failure. Mine went at about 100K miles when the car was 16 years old. I live in sunny Southern California so the switch got regular exercise, so to speak. In 1997, the part did not cost very much.
If you drive the car before getting the new switch, I recommend that you simply hook the wires together while you drive. The fan will tolerate that unless you are driving a really long distance.
I understand that you have an early model (1974 vintage) from another post.
For what it's worth, my later 1981 USA fuel injected model uses a thermo switch with only two wires. Since Hamish reports the same thing, I recommend that you obtain a two wire variant.
I join Mikele in reporting a thermo switch failure. Mine went at about 100K miles when the car was 16 years old. I live in sunny Southern California so the switch got regular exercise, so to speak. In 1997, the part did not cost very much.
If you drive the car before getting the new switch, I recommend that you simply hook the wires together while you drive. The fan will tolerate that unless you are driving a really long distance.
-
Andy
Re: radiator fan switch
Hmm. Plenty to think about there - thanks folks. To follow up a bit...
Hamish:
the fan wiring is normal (big black wire, big blue wire), but the switch, which is on the back of my old-style radiator, definitely has 3 wires, one of which is not connected to anything. I'll have to check again, but from memory the 3 wires are all black as they leave the switch, but connect to different coloured wires where they join the loom a few inches later: one leads to a ground post beneath the headlights (LHS for me), the other joins the loom but exits 10 inches along to connect to the fan relay. I'll check all these wires again before doing anything else. For a start, the in-line fuse holder on the blue wire from the fan looks like a fine piece of junk...
Mikele, Randy:
For peace of mind, I'll change the switch anyway and I'll take the 2-wire type this time. They're still fairly cheap. In the few days that have passed since I began this thread, the temperature here has dropped radically (it snowed at 3500ft yesterday...), which is great news for my cooling problems, but which also means that it's time for me to change the anti-freeze. The switch can go at the same time.
Alan:
Fortunately, despite all the other electrical madness in this car, my temperature gauge seems surprisingly reliable so I've been able to avoid serious overheating so far. I think I'll fit the manual override though.
Thank you all, and have a good day.
Andy
Hamish:
the fan wiring is normal (big black wire, big blue wire), but the switch, which is on the back of my old-style radiator, definitely has 3 wires, one of which is not connected to anything. I'll have to check again, but from memory the 3 wires are all black as they leave the switch, but connect to different coloured wires where they join the loom a few inches later: one leads to a ground post beneath the headlights (LHS for me), the other joins the loom but exits 10 inches along to connect to the fan relay. I'll check all these wires again before doing anything else. For a start, the in-line fuse holder on the blue wire from the fan looks like a fine piece of junk...
Mikele, Randy:
For peace of mind, I'll change the switch anyway and I'll take the 2-wire type this time. They're still fairly cheap. In the few days that have passed since I began this thread, the temperature here has dropped radically (it snowed at 3500ft yesterday...), which is great news for my cooling problems, but which also means that it's time for me to change the anti-freeze. The switch can go at the same time.
Alan:
Fortunately, despite all the other electrical madness in this car, my temperature gauge seems surprisingly reliable so I've been able to avoid serious overheating so far. I think I'll fit the manual override though.
Thank you all, and have a good day.
Andy
-
Keith turner
Re: radiator fan switch
Hi Andy
Me again according to the beta diagnostic manual the three wire thermo switch has 1 connection to the fan motor 1 to ground via the loom & 1 to ground connected to the copper sealing washer it has no relay the thermoswitch just shorts to ground when the temperature rises, the other side of the motor is connected to the battery via a fuse. All the diagrams I have including 1800 models show the same wiring - no relay.
Me again according to the beta diagnostic manual the three wire thermo switch has 1 connection to the fan motor 1 to ground via the loom & 1 to ground connected to the copper sealing washer it has no relay the thermoswitch just shorts to ground when the temperature rises, the other side of the motor is connected to the battery via a fuse. All the diagrams I have including 1800 models show the same wiring - no relay.