Fuse #1/A keeps blowing

[V12StealthHunter]

I recently got my car on the road after a mechanical restoration and have noticed problems with the circuit that goes through Fuse #1 (or A or the right most fuse). I know its part of the engine cooling fan circuit. I think it had a 16A fuse in it. When it blew I did the most obvious and most intelligent thing anyone would do and put in a bigger fuse! I put in a 25A fuse in it and it seems to be holding but I can see it getting slightly burnt on the edges of the fuse. What else goes through this circuit?

From reading the wiring diagram that came with my car, that fuse handles the cigarette lighter and the engine fan. Is there anything else its meant to protect?

How much current does the stock engine fan pull? What is the correct fuse size for this application?

How do you go about diagnosing a problem like this? I know I can measure resistance across the fuse terminals when the battery is disconnected but what is the magic number I'm looking for?

[azruss]

burning on the edge of the fuse would tell me your connection between the fuse and the holder is weak and you are developing heat there. clean the contact with a scotchbrite pad and pinch them together so they hold the fuse tighter. Is the fuse blowing the instant you put it in. If not, try to find what goes on that blows the fuse. It is possible your fan is doing that if it has internal drag.

[DieselSpider]

The owners manual that came with my 78 even though it says there is one 25 amp and one 16 amp fuse however it has the largest fuses in the listing that follows as 16 amp which is for I - (Horns/Engine Fan) and L - (Lighter/Clock/Courtesy Light/ Hazard Lights/Inspection Lamp/Key and Fasten Belt Buzzer/Motorized Radio Antenna).

Is the ground to the fan good and all the connections tight? It also could be the fan switch on the bottom of the radiator getting ready to fail.

[seabeelt]

You may need to isolate each item fora period of time and see if there is any change in the fuse condition. I would also look for burnt or frayed wires that might have increased resistance or shorting to ground

[spider2081]

I typed my thoughts this morning and must have forgot to post them.
My wire diagram for a 78 shows the cooling fan on Fuse #9. Fuse 9 and fuse 10 are "hot all the time" circuits. Your fan should be able to run with the ignition switch in the off position.

Fuse 1 is Switched power in the "start and run position of the ignition switch. I don't believe you radiator cooling fan belongs on this fuse. The radiator fan draws close to 15 amps when running.


Maybe someone else with a wire diagram could confirm t his for you.

[seabeelt]

The fuses are labeled, but just in case, fuse 1 is closest to the steering column

[V12StealthHunter]

Looks like someone has wired the headlights, radiator fan and cig lighter all on this fuse. I've just ordered some Bosch 0332019150 relays to take the headlights off the main fuse box.

[spider2081]

Headlights are usually on 4 fuses one for each low beam and one for each lo beam. Do you have an owners manual or a wire diagram for your car??? On my 1981 they are fuses C,D,E,and F

[azruss]

You have an early Spider and I think the headlight is on the always on fuse. The fan should not run after the key is off on this car, so it should be on the high amp keyed fuse. Others with early spiders can confirm this.

[spider2081]

My bad Not sure why we were talking 1978 Spider. I don't have a diagram for a 71 sorry for any confusion I caused.