SteveL

A few weeks ago I posted about my daughters new to her 2003 Mustang Convertible not cranking. With help on here I found out it had a fuse under the dash that was blown. Replaced the fuse and she has not had any issues until tonight, blew another. Replaced it and blew the new one right away. Third fuse it finally started.
Now I might be seeing a pattern here. The day the first fuse blew there was a light rain outside and she came home for lunch.
Tonight it was not raining, but she had just washed the car a couple of hours before the fuse blew.
I am wondering if it is possible she is getting water intrusion somewhere in the system?
Has anyone experienced water in a system causing similar problems? Where should I start checking to see?

Daehawk

Sounds like a short..no idea where.

SteveL

That is what I am afraid of. I am going to follow advice from my other thread from back when it wouldn't crank and replace the relay just in case that might be it.
I am not sure where to start looking for wiring shorts, sounds like a pita to me! I think first I am going to check fuse blocks to see if she is getting water intrusion. Maybe just a coincidence that both times the fuse blew it was wet, either rain or right after she washed it.

SteveL

I haven't had time to look into her Mustang until tonight. Earlier today the starter fuse blew again. It was not wet and she had not washed it, so that rules out the water idea.
I got under the dash and traced the white and pink and the grey and yellow wires as far as I could and did not find any shorts. I followed them to where they go into the thick taped up wire cluster. Next I traced the yellow and pink wires and did not find any problems. I did not unwrap all of the tape from the large cluster, but do not see any place where it could have rubbed or been pinched. I crawled under it and checked the wires to the shift position sensor and they look good. I then pulled the fuse block and checked the back side for corrosion or any bad spots in the wires. Everything still looked good.
Tonight when her fuse blew again, I replaced the fuse. As soon as went to start it flashed the new fuse. I had attached a long wire to the small lug on the solenoid on the starter and left it coiled at the back of the engine. I unrolled that and touched it to the pos battery post to start the car. When she got back home, put in a new fuse and it started.
Now I am wondering if there is a problem in the ignition switch?
I am about ready to run a wire from the battery through a push button switch down to the starter for her. I don't really want to do that for safety reasons, that would bypass the neutral safety switch.
Any ideas of where else to check in the wires? There is no rubbing on the brake pedal, no rubbing on the steering column.

SteveL

I am a little OCD when it comes to diagnosing vehicle trouble. After my last post I was thinking of the wiring diagrams I found for this circuit. I have a thought to throw out there.
The starter fuse under the dash will blow at random times. I have not found a pattern of what causes it to blow.
From what I can find out that circuit comes from power, the battery to simplify the idea. Power from the battery into the fuse box, then out to the ignition switch. From there it runs down to the shift position sensor (neutral safety switch). From that switch back out to the starter relay which when energizes puts power to the exciter wire, or the small wire to the starter. So, the short has to be between the fuse block down to the neutral safety switch. Now in my mind it most likely is not between the fuse block and the ignition switch because it wont blow until the switch is turned to the start position. Everything under the dash looks good, no visible shorts that I can find. In the daylight I will check the wiring down to the transmission closer.
A thought I had, the car is not going into overdrive. It shifts fine through all of the gears, but no overdrive. It does not slip or try to shift, it acts just like it is turned off. The OD off light is not lit up. Push the button on the shifter and the OD off light on the dash comes on but of course it does not shift down. No change in the RPM's or the engine running. I was suspecting the snap ring in the transmission had broke, but is this possibly an electrical issue? Any thoughts on the two problems being related?
I fought a stutter in my 2001 expedition for years thinking a coil was stumbling every once in a while. Then the tow/haul light started flashing and I lost overdrive. I found out the wiring to the transmission had melted to the exhaust and would short out.
Any thoughts on a possible relationship between the 2 problems?

Daehawk

I hope someone can help you. Ive never had this issue and it is also a bit slow around this board now days. I know most everyone that posts with questions are in a hurry to resolve their issue but its very slow here now. Im sorry. Ya never know though...someone with the exact issue may happen by with just the right answer for you. Can hope. Good luck.

The only thing I can think of is to trace the neg wire from the starter and look at its entire run. Make sure its not up against the EGR tube or anything hot that will melt it and cause a short. If I find anything online Ill post it. Really if the entire wiring is fine then it can only be the starter, the relay, or the switch on the column.

Keep in mind there is also a starter relay fuse in the box under the hood. Its a 40a. If its not blowing then its probably not the relay. One way to be sure is to remove the relay and put in a good fuse under the das hand see if it blows. If it still blows then its not the relay.

Heres a couple pics of one guys cause...wiring harness up against his EGR tube.

SteveL

I will take a closer look when I get time in the daylight.
The first time it did this, I did not know there was a fuse under the dash. I checked the maxi fuse under the hood, pulled the relay and checked with a meter and 12 volt power source and both were good. So, I pulled the starter and tested it with jumper cables and a battery. It worked fine too. THEN I discovered the fuse under the dash. I will have to do some more wire tracing to see where else it could be.
Thanks for your time!

SteveL

Well, she blew another starter fuse the other day. I got it into the garage and up on jack stands and visually inspected every inch of the wiring. I can not find anywhere that it is rubbing or melted or any other visible problems. I looked under the car at the wiring to the starter, the wiring to the transmission shift position sensor, and everything in between. The only place I did not check on the outside is the power distribution box. It is possible that there is corrosion under the box where the relay plugs in. I don't think the problem is there, it only blows the fuse about every other week. I got under the dash and looked at every inch of the wiring that I can see, it all looks good.
Last night I finally got the starter relay changed and I added a push button switch running straight from the battery to the starter solenoid for emergency use. If it wont start she can push the button and at least make it home.
I tried to isolate the problem by putting a new fuse in and turning the key while pulling the relay, but it started working right away. Sometimes when it blows the fuse I can replace it and it works, other times it will blow 2 or 3 fuses before it starts working again.
Relay is replaced, next I am considering replacing the ignition switch.

Daehawk

Thats just damn random. I hate that type problem. The push button switch was a good idea.

SteveL

Yeah, I hate bypassing a problem instead of finding the root and fixing it, but this is my 16 year old baby girl. The button is not the safest because it bypasses the neutral safety switch, and she will have to remember to turn the key to run or she will wear the battery down. But I wanted to make sure she could get herself out of a jam if needed. We live in a small town of about 1000 people, mostly a farming community. Everyone knows me because of my job, and everyone knows her because of me and because she works at the local grocery store so if she has a problem here in town she will only have to sit there for a couple of minutes with her hood up and she will have help. BUT she does like to go out of town. A larger city is about an hour away. I don't want her to be stuck that far from home in a city where she doesn't know anyone with car trouble. In the unlikely event that someone would be harassing her and she needed to get away, I don't want her to be sitting in her car helpless.
I will keep searching for the cause of this problem, but until then she is at least able to get on the road.
Now I just need to decide what to do with the transmission. Shifts fine, runs great, but wont go into overdrive. I do feel a vibration at low speeds. It is not a rotational vibration like a tire issue, it is more of a constant vibration. So, next warm day I am going to get the back end up on jacks and check it out. I want to double check the U-joints and check the oil in the rear end. I was hoping to find a bad wire that was holding the transmission out of OD, but whenever I have had wiring issues the OD light will usually not work at all or will flash. This one, when you push the OD button the light comes on saying OD off but no change in engine rpm's.
In college I torn down and re-assembled Chevy th350 and th400 transmissions, ford c4 and c6 transmissions, even an FMX but I don't think I want to dig into this one. I suspect that the snap ring is off of the actuator above the valve body, but am just a little scared of dropping the valve body and messing something up.