fan - lower turn on setting

[geoff]

I have had a few problems with overheating in towns and my local garagiste told me to change the fan switch to a lower switch on temperature type. The original closes at 95°C and opens at 90°C and this new one I just fitted closes at 60°C opening at 50°C.
What do you think, is this a good move ?

[Nut124]

Are you talking about a thermostat or a fan switch? The thermostat controls the engine temp, not the fan.

If I were to lower the running temp of a FI car, I'd study the cold start system and make sure the ECU thinks the car is up to temp at the new setting and not in cold start mode.

I put a lower temp thermos and a fan switch in my -78. But they are only like 170F vs 190F. Going from 90C to 50C seems drastic and it would seem unlikely that the cooling system could keep the engine that cold during hot weather due to the small temp differential.

[geoff]

I am talking about the fan switch. I have yet to take the car out following fitment of the new switch, but I do worry that the fan could now be almost permanently on.

[18Fiatsandcounting]

I am talking about the fan switch. I have yet to take the car out following fitment of the new switch, but I do worry that the fan could now be almost permanently on.

I think you're right to be concerned. If the fan switch really does turn on at 50 oC (or even 60 oC), the fan would be on all the time. "Fully warmed up" coolant temperature for these engines (and most engines in general) is 190 to 200 oF, or 85 to 95 oC or so.

-Bryan

[TX82FIAT]

Captain obvious for a second. Fix the reason problem with the overheating first. A lot of modern mechanics have issues burping the air out. Also, when did it start overheating is this a new issue or has it always done this. The replacement of the fan switch is like taking a pain pill. It only improves the situation for a while but does not fix the underlying problem. A new fan switch is not a fix. With that said, I use a manual switch wired in line with the switch at the bottom of the radiator and turn it on when temps are over 100 and I know it will be three of four red lights before I get through the traffic backup. This is an once of prevention to keep the car cooler in traffic to reduce stress on the cooling system expanding and contracting. Car will not overheat without manual switch, it just keeps it more consistent.

[geoff]

I take on board all you say and I agree in pricipal. However, I think that it would be good to know the normal working temperature of the coolant - AT THE POINT OF THE FAN SWITCH - because surely the "normal" working temperature differs at various points on its journey?

[18Fiatsandcounting]

You're correct in that the temperature of the radiator can vary depending on location, but this difference is fairly small, maybe 10 oC in different locations. When the engine is fully warmed up and you're driving along at 3000 to 4000 rpm (water pump spinning away), the coolant should be pretty similar in temperature throughout the system.

However, if the radiator is restricted (crudded up) or other parts of the cooling system are marginal, there can be more variation. Unfortunately, the area where the fan switch is located (bottom of the radiator on the driver's side) seems to be an area that is prone to corrosion build up and such, so that yes indeed, the fan switch might be seeing a much lower temperature than the top of the radiator where the coolant enters.

So, TX82Fiat has a good point in that you may have blockages in the radiator or elsewhere that are causing the issue with the fan switch not coming on. It could also be a worn water pump that isn't moving coolant as fast as it should.

-Bryan

[TheBender]

I’m with Bryan and TXFiat. Diagnose more and track down the issue causing the overheating. I live in Texas and sometimes drive in 100F+ temps and no over heating issues. I’ve got the basic radiator from AR and I believe a standard fan. If it’s working properly, it will keep it at the right temps.