Temp gauge

The electric fan motors get old/rusty/sticky from sitting around so long (or just wet from washing or rain) because people drive these cars less than other models...

That initial stickyness increases the surge current, sometimes blowing a fuse. No big deal.

$0.80 for an NTC thermistor strikes me as a pain-free fix. Either that or convince people to drive 'em more.

 

My 19 year old 328 sat for 2 years one time (under my "watch") without ever being started. I'm also very "liberal" with water. I spray it everywhere, under pressure. With the previous owner the car also sat for extended periods of time. He was 61 years old and had 17 Ferraris in his garage (along with other daily driver cars) when I went to visit him and bought the 328. Needless to say, it did not get much use. Never blew a fuse. My 1972 Fiat-Abarth 124 Rally had an electric radiator fan, did not get a lot of use and never blew a fuse.

If an 80 cent thermistor fixes the problem then that's a good thing. Personally I would want to investigate and solve the real problem but that's just a matter of curiousity, the challenge and hardheadedness on my part.

 

There is no discrepancy in the fuse ratings between the owner's manual and the fuse panel, there was a confusion about which model we were discussing. Yes, there is an issue with the fuse rating on the 355 (30amp fast blow), or something. But there is no commonly available slow blow fuse in the ATC blade type. There are breakers available though. I have not seen a need for slow blow fuses in any other car with electric radiator fans, so obviously there is a problem with the motors used or the circuit design. What ever the problem, it seems that either 40 amp fast blow fuses or an automatic resetting breaker solves the issue. I am tempted to get some 30 amp breakers for my 355, even though I have blown a left side fuse only once, just because they never blow at a convenient time, and having a permanent solution appeals to me.

 

But do we know if other cars in fact have some sort of surge suppression circuit? Such as a metal oxide varistor or NTC thermistor?

 

As far as I know other cars do not have a surge suppression circuit but I don't work on cars for a living and I'm not familiar with a lot of different brands. Why wouldn't wiper motors have them then? Or interior fan motors? Sunroof motors?

Are you sure that a "fast blow" fuse is specified for the radiator fan motor or are you assuming that it should be fast blow because slow blow is not specified?

This topic reminds me a bit of the "window accelerators" that are available. There should be absolutely no need for them (had things been designed correctly by Ferrari) however there seems to be. How many other cars need "window accelerators?" Maybe the original window motors are too small (not powerful enough), the grease in the window channel tracks is too thick or hardens too much or not enough was used, maybe relays should have been used but were not, the wiring guage is too small, the connectors are low quality and develop resistance, the ground points were not well done, a combination of all?

 

What about trying a "normal" fuse? (not fast blow and not slow blow).

Is it possible that there is an error in the specification? Maybe they did not mean to specify a fast blow fuse. As I mentioned before, it just does not seem right to me that a fast blow fuse would be specified for an electric motor application. It would be a pretty basic error but I suppose stranger things have happened.

What about contacting a specialist automotive electrical garage and getting their input/opinion?

 

If you use an NTC thermistor, aren't you going to extend alternator and battery and wiring life due to lower current surges?

Were these devices even around back when the 348/355 were being designed?

 

There would not really be any effect on battery, alternator or wiring life. Starter motors draw hundreds of amps for a short period of time when you start a car, with no ill effect. Now that's a real surge.......

Thermistors have been around for a loooong time (although I'm not sure how long for ones specifically for inrush current applications).

 

On my 348 spider, my dash lights will dim momentarily (basicly, a single "flicker") right when the main radiator cooling fan kicks on. I think that Goth even said that his RPMs would drop on his 355 Spider (more electric drains on his model, of course) when the main rad fan kicks on.

His solution, which I added to my 348, was a fan shroud (AKA "Gothshield"), but I wonder if current surge is also part of that RPM drop on 355's. If so, then it seems to me that finding the design issue or adding the $0.80 NPT inrush thermistor to the main rad fan would be smart.

 

That is all normal. When an alternator is "asked" to produce more current (because you turned something on) a side effect of the increased current supplied is that the alternator is harder to turn (more drag). It requires more effort (hp) to turn it. This will cause an rpm drop (if it's a high current customer like a rad. fan) which is then compensated for by the idle control motor on a modern car (if everything is working correctly). Some cars even have a software strategy to raise idle just before the A/C clutch, for example, is energized so there is little or no drop.

Again, when an electric motor starts it requires a lot more power to get it spinning than to keep it running. A momentary dimming of the lights is not unusual and even a voltage drop (not just momentary) is normal.

If I had this problem with my car I think I would run a larger wire to the fan motor and install a 40 amp fuse. A circuit breaker would be a solution to having to replace blown fuses now and then but my concern would be more about being "notified" of a blown fuse or tripped rad. fan circuit breaker. The big worry and expense here is the possibility of overheating the engine. A flashing light and buzzer could save the day. Still, it's only a band aid for the actual problem (whatever it is!)

 

It's true that dimming (or more) is normal when a large fan kicks on, but that's because it is so common to simply turn on such motors fully, rather than gradually over a tenth of a second or so.

It's not as though your radiators or engine will notice any negative difference in taking .1 seconds versus .2 seconds for your cooling fan motor to reach peak speed, but the *rest* of your car will have less stress, I'd wager, if the turn-on was more gradual.

 

It has to be the thermal switch on top of the LH radiator mine would not start the radiator fan until about 210F-ish... ....... $20 bucks from Ricambi and the temp stays at 190 steady !

Easy to find when you remove the LH front wheel well liner !

 

Low coolant
Old coolant
Newspaper or debris covering radiator grill
System needs bleeding
Low engine oil
Old engine oil

String/rust/debris obstructing fan motor axle (to fan blade)
Radiator(s) gone bad internally
Alternator isn't outputting enough juice to spin cooling fans fast enough



Or the really bad possibility: shot water or oil pump.


Check the above list in order for the best chance at a low-cost (and fast) fix.

 

I mis-typed............. front portion of the LH rear wheel liner.... just behind the LH radiator.... !!

 

But he says his fans are coming on. Can't be a switch issue if the fans are coming on, right?!

 

My thermal switch was "degraded"..... it still switched on, but at a higher temp of 210-ish..... ..... after I replaced it, the fan comes on at 190f everytime...

 

Ahhhh!


Thank you for the explanation.

 

If one were to use an automatically resetting 30amp circuit breaker, then WHY would you need to be notified? It will automaticallly reset itself, once the transient "surge" has passed, which I would assume is very fast...probably fractions of a second. Then the fan will operate normally again. You are thinking of a manual resetting circuit breaker, which would require you to push or reset a button. That would not be appropriate for this application, as it would not be of much benefit over a standard fuse, since your only indication of a failure is no fan operation, and an overheat situation.

This is an example of an automatically resetting circuit breaker:
http://www.delcity.net/delcity/servlet/catalog?parentid=151&childid=46529&page=1&pageitem=2&tabset=1

 

I agree, there would not be a great benefit using a breaker that has to be manually reset. Still, if I had an automatic resetting circuit breaker I would like to know how often it trips and for how long. Does it only trip at start up? What if a different problem develops and current is too high when the motor is operating? The auto reset breaker will continue to open and close and you may not know about it until if fails (possibly).

If the auto reset circuit breaker uses a simple bi-metallic strip (most likely) I would not assume that it will close VERY quickly after the start-up surge. The metal has to cool down. Now, if it takes longer than "x" amount of time the radiator fan motor will have stopped again and in theory you could have the same overload surge when the breaker contacts close again to run the motor. You could have an endless cycle (all theory). Think of an inexpensive toaster...... the toast pops up but it's not dark enough for your taste, you push the lever down again to toast a bit more but the lever will not stay down (latch) until the bi-metallic strip cools down. Okay, it's a very different application, voltages, heat level etc. Just trying to make the point that the breaker may not reset as quickly as you think.

In any event I'm not sure there is a lot of point to debating ideas/theories. Why not try the auto reset circuit breaker and see what happens? It's cheap and may solve the problem. If it doesn't solve the problem then that can be eliminated too, as a possible fix action. A win, sort of win situation.

 

I don't really have a problem. I have only blown a fuse once, over a year ago. There are others that blown them every few months. Just trying to find a solution for them, and the automatically resetting circuit breaker seems the best solution. Remember, the fuses blow every few MONTHS OR WEEKS, not constantly.