Hi all For a while, I've had 0/4 solenoids working on my 89 Mondial T. Frunk, trunk, engine, fuel flap - all fried. Red bay was the final step in scrounging up replacements, and I am slowly getting around to replacing them. Before I finish up, I got to be thinking - should I be adding an inline fuse or something to prevent this from happening again? Any ideas on what value to use? Thanks Sam
If you connect an ampmeter to a new one on the bench, test it and thats your operating current, if you want a fuse then add a bit to it. I think you may be able to get anti surge fuses which might help. Not my area but worth thinking about
Ferrari did a thermal cutoff upgrade kit for the trunk/hood/engine solenoid to protect them. In later models ('90+) seems it was standard. Kit is NLA but I guess it can be duplicated. Image Unavailable, Please Login
+1 -- A solenoid burning up is caused by keeping it "on" too long, not the current being higher than it was designed for (so adding a fuse would do nothing -- it probably already has a fuse that isn't blowing now). Maybe you can say that doing a design where the intended current can be applied for a long time, yet the solenoid can't survive that current for a long time, isn't a good design, but the designers had the conflicting requirement of needing a very high force from the solenoid (which requires a high current) and maybe (wrongly) relied on the operator to not "keep the button pressed for too long during opening" -- and if something gets wonky in the mechanical bits of the system = the operator will press the button longer/more (rather than fixing/adjusting/lubricating the mechanical bits).
Thank you all. I did try to measure with my VOM, but my 12V power supply wasn't kicking it very well and I didn't want to hold it too long. If I'm reading this correctly, the coil is 0.175 ohms? So that's 68.57 amps? That matches the markings on one of my solenoids. Is that OK because it is so quick, or am I calculating this wrong. Evidently the fuse wouldn't be useful anyway. One of my coils did have the thermal protector on it. Also referenced in this thread: https://www.ferrarichat.com/forum/threads/mallardi-solenoid-protector-oem-style.628037/#post-147415172 "1D05658 made by ottercontrols.co.uk. While obselete, there is a replacement that can be directly ordered from otter: F07375 QR181CA000 BR 27A B3.5-5.0 A80" Mine is marked Otter 2605658. I cannot find this part, or the on referenced above I emailed Otter directly last Tuesday, but have not heard back. Does anyone have a line on these? Thanks Sam
That was the plan -- even though the current is high, the time is supposed to be short. One refinement on your calculation is that it only applies when the wire of the solenoid is at room temperature (your multimeter uses a very low current to measure resistance). When such a big current actually starts flowing, the wire of the solenoid coil will heat up, which will increase its resistance, and drop the current some -- like maybe down to ~50A for a 100 deg C temperature rise -- at which point all of the plastic of the solenoid fries . To scare yourself even more do a power calculation: 12V delivering ~65A = 780W -- better not run that hairdryer very long if you don't want to melt everything.
Make sure the switch push buttons are not sticking when pushed. Seems to me this is a culprit- current stays on until something burns up due to the stuck switch.
I'll second this advice! The switches were the culprit in my "solenoids not working" saga. Some Deoxit inside the switch body cleared everything up.
