Electric Fan Control

Gentlemen may I have your attention please. Reading all my posts you can’t tell the appreciation I have for the 355. Honestly, there isn’t a more perfect car in my opinion. Because I like this model more than anything rolling on four or walking on two, I will attempt my co tributes to its form and function some way or another. Having said that I’ve been contemplating on two projects. One is currently in the process. I will have the finish product hopefully by mid March. If I can keep the cost low and quality on par with Ferrari reputation, I will show it here. If not, the project will be trashed and the blueprint shredded. My second project, I need to do a bit of research and what better way to get the right informations than here in the 348/355 forum.


The 355 is phenomenal car in form and function but some of the gadgetries and control could use an update. One I will attempt to upgrade is the fans control. The period between the fan on and off is a big gap. The temp gauge has to go past the middle mark for the fan to come on. When it does, the temp needle has to fall back to the 3/4 mark below the middle for the fan to shut off. This gap is too great. The temperature swing is too much. I believe the 355 engines run better when the temp gauge idles near the middle mark with little fluctuation. Theoretically, it can be done. I just need to find a few electronic parts and put them together. My question for everyone, we know the fans are controlled by a temperature gauge. Does anyone know if it’s an air or water gauge and at what temperature setting activities the fans? I am certain every 355 owners will benefit if I have all the infos and available parts. Thanks

 

Ian, great dig up. Im too lazy to read the manual. Reading was never my favorite subject since grade school. I preferred recess and lunch. Anyhow Im amazed by the complexity of the 355 control. The simple process of lowering the spider top requires 5 limit sensors and a trigger switch independent of normal control switches. The control circuit has to be an “AND” logic which mean window left AND window right AND seat left AND seat right AND the roof latch has to be unlatched for the top to open. Either one of the sensors failure, the roof will not open. Ferrari had to know the error factor is 5 fold and because these are moving sensors with a margin of error within fraction on an inch. The seat limit sensors could have been a $5 bullet proof single pole double throw micro switch. The good news is nothing is impossible. Existing control can be replaced but who is motivated enough to replace all the switches in the windows and under the seats that requires drilling not to mention the costs. I like to mention, the problem has more to do with the sensors not the “ECU”. Oh, shoot I’m off topic.


I thought the fans control is much simpler. I would have never imagined Both fans are controlled separately by coolant temp and oil temp. This throws a monkey wrench into my plan. I suppose the only way to get an accurate temperature reading is by coolant temp. I’m hesitant to drill or tap into anything 355. My idea is to add an adjustable air thermostats to turn on the fan at half the speed between the on/off gap of normal operation. Will maintaining the working of existing control. I suppose if I can find a spot in the engine compartment where the temperature varies proportional to the engine temperature it could work. If anyone wants to tackle this project, we can partner up. I can design the circuit, get the pieces and put them together. What I need is to locate an accessible spot in the engine bay. Get temperature reading when the fan(s) comes on and when it turns off wile the car is in motion. If we can get consistent readings at different time of day, it could work. I M not motivated enough to do the experiment in my spider. Too precious.

 

No rhyme or reason. Just curiosity hoping to make good better. A while ago someone mentioned the fans situation as I stated in the first post. Mine does the same and I’m convinced all 355 electric fans behave the same way. So why does it matter? Well, correct me if I’m wrong. Combustion engines operate at their max potential at an ideal temperature. The low and high between the fan(s) off and on as indicated by the temperature gauge in the 355 while running is too wide. I speculate at least 50 degrees or more. What if it’s possible to reduce the gap to less than 30 or even 20 degrees. Well, I believe it can be done. Hence, my inquiries.


From informations provided by Ian and Chan, it seems Ferrari got all bases covered. Multiple layers of temperature sensors make sense given the 355’s has a high strung, high performance engine. Coolant, oil, engine compartment ambient temperature to work the fans. Not much room to improve on except to make it more precise by reducing the gap thus reduce temperature variations between high and low. The obstacle is I don’t have a 355 fan laying around to get my hands on and I’m not about to take mine apart to dissect. If all things normal applying electrical common sense, I don’t need to see a DC motor to know it’s operating characteristic but given Ferrari over engineering nature, it’s hard to be certain. Does anyone know how many wires go to the fan?


Again someone correct me if I’m wrong. By observation, the fans are either ON or OFF which implies there is no speed control. I know the fans have DC motors. The speed of DC motors is easily controllable by voltage or current. If my assumption is spot on, adding an ambient temperature sensor, calibrated to within the high and low and wire the fan(s) to half the rated fuse size, keeps the fan(s) running at about half speed. The fuse, temp. sensor can be sized and calibrated to achieve an ideal temperature range.


Here’s the logic. Let say the fan(s) comes on when temperature reaches 215 degrees and cut off at 170 degrees. That’s 45 degrees swing. Now let say an additional control is added to turn the fan(s) ON at half speed when temperature reaches 200 degrees and OFF at 190 degrees. Theoretically, temperature gauge will lingers much longer at about 200 degrees. Overall environmental factors dictate whether temp. rises or fall. Likely fall slowly and turn OFF at 190 degrees. At which point rise again keeping overall engine temperature between 190 and 200 degrees. All without tapping or negating original control circuit. I think it will work. The result however, is my theory until proven to be facts. Facts achievable thru tinkering temp. sensor and fuse size. That’s not a theory. I made a sketch of a multi layer control circuit if anyone wants to tackle it. I’m not about to mess with my first 355 Spider. I won’t be able to give myself if I put a scratch on it. I ha e my priority.

 

It is redundant but maybe more than meets the eyes. If those temperature sensors monitor many areas of an engine; oil, coolant and engine bay ambient temperature. That’s three zones of coverage. All crucial to a race engine.

 

My car runs fine. My intend is to add to the anything 355 bucket of knowledge. Awhile ago someone mentioned if there’s a way to keep the fan running at lower speed so the fan(s) doesn’t cycle too much between the OFF and ON. I didn’t think there was a need for it. Now that I notice the temperature in my car swing quite a bit, I thought it would be a good idea to add an additional control circuit to minimize the cycling. The temperature swing is probably normal in the 355. I just find it odd given every car I own past and present, the needle kinda stuck in the middle once the engine warns up. Someone else can co firm or debunk this, even if the needle only move slightly, it’s more than 10 degrees.

 

Here’s my logic follows by reasons. Cars electrical system operates on Direct Current. Therefore all electric motors in a car is a DC. There are many types of DC motors. Applications that require lots of torque such as a fan or the F1 motor is likely the Series type since Series Motors offer better torque curve than the other types. Series type motor gets its name due to the fact that its magnetic field windings is electrically in series of the armature. The speed of all DC motors depends on the strength of the magnetic fields which is proportional to the net power(VoltAmp) input. By varying VA input, the strength of the magnetic fields varied in strength thus the speed of the motor. The best way to reduce a DC motor speed, in the case of the 355 electric fan(s) is to limit the amount of current to the field windings. If the original fuse size is 20 amps, theoretically the speed of the fan(s) is half if a 10 amps fuse is in line instead of the 20 amps. Alternately, the speed can be co trolled by varying the voltage to the field windings. This method requires a resister in line with the motor. The inline resistor acts as a load by reducing voltage. In the process it creates wasted energy and heat. The only time this method I see preferred, is when an application require a motor to adjust speed infinitely by adjusting the resistance of the rheostat, the speed controller.

I thought the 355 fan(s) is either ON or OFF no speed control. Are you sure there is a resistor in-line with the fan(s)? This makes no sense but given what I learn the way Ferrari did things back then. “potientiameter” under the seats??? What for? When the spider top engages to open, the “ECU” asks itself are the seats in the designated forward position. If not move the seats forward. When the top engages to close, the “ECU” just need to know are the seats in the designated rear position. If not move the seats back after the top closes. That’s all. The “ECU” doesn’t need to know where the seats are at every position. It doesn’t need to know how heavy the person sitting in the passenger seat or if she’s wearing panties. I have seen the “potientiometer” just going by informations posted on here.

 

Image Unavailable, Please Login Gentlemen, I think we have a eureka moment. For those who insists having the fan(s) runs at half speed, the diagram should get you going. Line 1 and 2 are existing control circuit. Line 3 and 4 is added. Exiting control is not altered in any way. When it triggers the fan(s) to come on, secondary control (line 3 and 4) open up and isolated from the circuit. Secondary control (line 3 and 4) trigger the fan(s) at 185 degress. Fuse and resistor size can be adjusted to desire speed.