Cooling fan not coming on

[mglisson]

My '79 spider has begun to overheat. I have determined that the elect fan is not turing on. Where/how do I check fan, then
radiator fan swirch(?). Or what else? Help
Rookie in Louisiana

[4uall]

This might help

http://www.fiatspider.com/f08/viewtopic.php?f=5&t=2494

[toplessexpat]

Unplug the two wires that come from the temperature switch fitted to the bottom left hand side of the radiator. With the ignition on, connect the two ends that you've disconnected from the switch. The fan should come on - if it doesn't then there's something awry with your fan or power to it, if it does come on - then it's your temperature switch.

[mglisson]

WOW great info thanks. I'm back at it tomorrow
Mike

[So Cal Mark]

just jumpering the switch isn't the end all. If the thermostat isn't opening then the switch won't reach closing temperature, or if the radiator is plugged the switch won't reach closing temperature, or if the water pump isn't pumping the switch won't reach closing temperature

[toplessexpat]

just jumpering the switch isn't the end all. If the thermostat isn't opening then the switch won't reach closing temperature, or if the radiator is plugged the switch won't reach closing temperature, or if the water pump isn't pumping the switch won't reach closing temperature

Mark's right - but you can rule out the switch if nothing happens. If the fan does work, then you need to look at why the switch isn't working .... Broken switch, broken thermostats meaning the switch never gets warm enough to come on... Etc etc (taking the switch out, putting it in boiling water and checking the resistance across it works for that)

A

[DieselSpider]

On mine the wires potted into the switch rotted out just below the surface and so that the insulation was all that was holding it together. If the radiator is getting hot and it does not overheat while moving then chances are that the coolant is flowing. I started by quickly splicing in a toggle switch parallel to the fan switch to turn on the fan and then sourced an external fan switch from the local Advanced Auto who had an adjustable unit on the shelf for less than $20. I have kept the toggle switch under the dash just in case and have used it to cool things down more quickly when I need to work on the car and its just too hot outside to deal with working on it while the engine is still at operating temperature.

[mglisson]

Ok my fan workes. For around $15 for a new switch, it would seem the easiest next step would be to replace it. If I decide to put the switch in boiling water - how do you know when/if it closes?
Mike

[toplessexpat]

Measure the resistance across the switch - my multimeter has an audible beep when there's a connection (ie v low resistance). Put the multi meter probes together, set the meter to resistance (it might say "ohms" or something else), and see the display at zero (or the meters is beeping). Now connect the probes to each side of the switch using the pigtails, put the switch in a saucepan of water and heat.... If you've got a thermometer you can see at what temp the switch is opening too.

Bear in mind Mark's comment above - if the switch is good.... Then you'll need to start looking into your cooling system components - Starting with the thermostat (don't put the saucepan away yet.... You get to boil them too to test!)

A

[mglisson]

Thanks again for all the info from fellow Fiat Spider lovers
Mike

[DieselSpider]

Quick test is to just pull the connector off the switch and bridge the leads so that the fan stays running and if the fan does not turn or its a bad fan or fan circuit. If the engine stays cool after you wire the fan to stay running then its just a bad fan switch. You can also place your shop fan in front of the radiator to provide air flow to verify that the rest of the cooling system is working.

Mine started to overheat the first time I left it idling in the driveway with the symptom of the fan not turning on so I just put the shop fan in front of the car and it immediately started cooling down so I was pretty confident it was just a bad fan switch which I verified by taking readings with a thermometer to see if the radiator was getting warm enough to trigger it and then by checking for damaged connections which I found in the form of failed wires leading into the switch.

A $10 non-contact thermometer from Harbor Freight will verify if the radiator is warming up past 180+ degrees.

Myself I did not like the looks of the bottom of my radiator so I did not chance removing the original fan switch and tearing out the mount from the bottom of the radiator.

[mglisson]

I think I'll try that now that I know my fan works....what if the temp goes down as long as I am moving (driving) and goes up when I have to stop for a short period like at a red light. That is what was happening when I first noticed the temp going up. Wouldn't that be the same as you fan technique?
Mike

[toplessexpat]

It could simply be that there is air in the system. The highest point in the circuit is not the radiator cap - hence why one of the filling recommendations is to jack the front of the car up so it is. Another is to install a "T" in the heater hose that loops over the passenger side cam box from the pipe that runs straight back from the water pump to the top of the head (as that is the highest point), and fill through that.

Checking you've not got air is probably sensible!!

A

[DieselSpider]

I think I'll try that now that I know my fan works....what if the temp goes down as long as I am moving (driving) and goes up when I have to stop for a short period like at a red light. That is what was happening when I first noticed the temp going up. Wouldn't that be the same as you fan technique?
Mike

Yes if its cooling when the car is rolling and does not cool when its standing still would seem to indicate that coolant is flowing and you simply have an issue with the fan not cycling. The switch has probably failed yet it could also be sediment in the bottom of the radiator however that would have to be a pretty extreme case for it to insulate the fan switch and prevent it from switching on.

[toplessexpat]

DieselSpider - sorry to disagree, but on a stock spider set up that's not exclusive behavior. Cooling when rolling, and rising in traffic is also a symptom of air in the system, regardless of fan behaviour. Indeed - I've had a stuck thermostat, with no coolant really flowing, and the temp cooled when rolling!

Plenty of threads on getting air out of the system. Here's one http://fiatspider.com/f08/viewtopic.php ... verheating

In fact - I've been running around for a couple of weeks in my 1800 knowing I had a small bubble left in. Drove to work this morning watching the gauge rise in traffic, fall on the open road. It wasn't overheating, just rising. Came down from the office at lunch, bled it out the T, and drove home - solid as a rock at 90.

If you're sitting in the garage, watching the temperature go up, having your thermal thermometer pointed at the radiator and watching the temperature going up as the thermostat open and coolant flows - and the fan never comes on before the needle buries in the red (and you've tested the fan and found it good), then sure the switch is the likely culprit.

A