Starter Relay fuse blew...replaced and immediately blew again.

[88CougarMan]

Ok, so I go to leave work and my car won't even make a noise when I turn the key. Stereo and lights and everything work fine. I check the fuses and the Starter Relay Fuse (20amp) was blown. I get a ride to AutoZone and get another fuse. Put it in and it still won't start, pull the fuse and it's blown too. So, I guess my relay is dead and it's causing the fuse to blow. My question is, where is the starter relay? Pictures would be helpful, because I'm going to be replacing this thing at night, in the parking lot of my work.

Thanks guys.

 

[jstreet0204]

 

[88CougarMan]

Thanks. I couldn't get the relay tonight as to only the Ford Dealer selling them. So, tomorrow I'll pick up the relay and see if that fixes it. However, I tested the relay with the Multimeter and it showed the correct points closed and the correct points open. So, with the relay out of the car and no power going through it, it shows to be working properly. So, does anybody have any experience with this issue? Why would the fuse be blowing?

 

[88CougarMan]

Would a bad ground on the starter cause the fuse to blow?

 

[n0v8or]

I don't have my wiring diagram handy at work, but I think the 20A fuse that popped protects the solenoid that pushes the pinion gear forward to mesh with the flywheel ring gear. It does not protect the starter relay.

What this means is that the problem is probably not the relay (though it is remotely possible), but either a short to chassis in the wire to the starter motor, or a bad winding in the starter. I would check the small wires to the starter and the resistance of the solenoid before buying a new relay. A 1 ohm solenoid resistance equates to a ~12 amp current, which is less than the 20A fuse rating. Any resistance well under 1 ohm would be suspicious. The resistance can be measured at the relay socket between the contact terminals and ground. Disconnect the battery negative cable before making any measurements.

 

[n0v8or]

OK, I got my wiring diagrams. They are for '03, but I expect '04 should be identical. Forget most of what I wrote above; it is probably wrong .

There are 2 fuses that protect the starting system. One is located near the battery, and the other on the underside of the instrument panel.

The fuse near the battery is labeled "starter relay & ignition" and is supposed to be 40A. If that's the fuse that is blowing, my previous message applies.

The fuse under the I/P is supposed to be 20A, and labeled "starter relay & radio". It protects the circuit that powers the relay coil. A red / blue stripe wire runs from the fuse to the clutch switch (manual transmission) and park/neutral switch (automatic transmission). From there, a white / pink stripe wire runs to the starter relay coil.

I have seen a previous message on Stangnet where one of the pedal arms chafed a wire and caused a short, so that is the first place I would look. A/T cars have a jumper in place of the clutch switch, and M/T cars have a jumper in place of the transmission park/neutral switch.

While a shorted relay coil is a possibility, this to me would be rare. You can remove the relay and check the coil resistance with an ohmmeter. It should be no less than 25 ohms.

 

[n0v8or]

Also, does the fuse blow with the starter relay removed? If yes, that eliminates the relay as a cause - don't bother to buy a new one.