ALT fuse keeps blowing

philly_blunt · Jun 11, 2007

I had the alternator and battery checked. I replaced the ground wire for the battery and made sure all connections were clean and tight. The fuse doesn't blow right away. When I idle the battery gauge stays in the middle and a little above. When i go to drive it and give it some gas, i see the battery gauge drop and the fuse blows. What could be causing this? My friend said check all of the alternator wires and the fuel pump? I am not sure why he said the fuel pump? Maybe because it blows when i go to drive it? PLEASE HELP!!! this is driving me nuts!!

philly_blunt · Jun 11, 2007

Anyone have an idea?

HISSIN50 · Jun 11, 2007

I agree. Check the regulator wiring.

It sounds reasonable that if there is a wiring issue, it's in the stator circuit or the sense wire circuit. The sense wire is likely. Pull the regulator wiring harness loom back and examine the wires for vulcanization (it happens on these cars).

Pull the fuse and check the terminals to make sure they are not hogged out (creating a loose fuse connection).

There is a wiring work-around for the sense and stator wires but it requires one to be totally sure the rest of the wiring is up to par - it's a last resort type of thing.

Good luck.

True 5.0 · Jun 11, 2007

I had the same problem! I fixed it by replacing the both the brushes and regulator.

philly_blunt · Jun 12, 2007

Hissin50 and true thanks for the info. Hissin, I replaced the harness and I thought all was well. I drove it to my brothers house who lives about 15 min away. Made it there and back fine without blowing a fuse. But, this morning on my way to work, I was driving for about 15 minutes and the fuse popped. I could tell because the battery gauge drops dramatically. Could i possibly need a new charge wire too? I was thinking it was because it was getting too hot. the charge wire seemed to be really hot. Maybe a bigger fuse? I'm not the best with electrical so any help is very much appriciated.

philly_blunt · Jun 12, 2007

Also, my air bag and check engine light are on. Could those have anything to do with it? I need a scanner. Doesn't murray's or autozone rent them?

HISSIN50 · Jun 12, 2007

I'm starting to wonder if you have some sort of internal alternator issue going on.

Would it be feasible to take it to the parts store for some testing? Have them keep testing it many times in a row. The last time I did one (for a GM), I had the guy keep cranking and cranking on it (I suspected I lost a diode) and it finally got hot and showed that not only the diode was bad but that the rear bearing was overheating. Since there is a heating or durational element with yours, this is an approach I'd take.

PUll codes before you disconnect the battery. Whether a parts store will pull codes seems to depend upon the region/store.

Good luck.

philly_blunt · Jun 12, 2007

I had the alternator tested, but I didn't have them repeat the tests. I will try that out today since it only takes like 5 minutes to take off the alternator. If I was going to replace the charge wire, can I run it right from the battery with a fusible link between the two?

HISSIN50 · Jun 12, 2007

philly_blunt said:
I had the alternator tested, but I didn't have them repeat the tests. I will try that out today since it only takes like 5 minutes to take off the alternator. If I was going to replace the charge wire, can I run it right from the battery with a fusible link between the two?

It's best to keep the charge cable going from the PDC to the alternator's charge stud. You'd have to use a couple of fusible links. As an alternative, I chose to use an ANL fuse/fuse holder. I like the idea of being able to swap a fuse on the side of the road (homie aint soldering anything roadside).

I have to wonder if the sense circuit isnt the issue though - you're blowing its fuse, not the OEM fusible links for the charge cable.

Good luck.

philly_blunt · Jun 13, 2007

Yea I dont know whats going on. When I went to restart my car after the alt fuse blows, I have to pump the pedal to prime the fuel system. Why would that be? I am going to change the fuel filter today and rent a scanner (You get all the money back). Thanks for all the help!

HISSIN50 · Jun 13, 2007

philly_blunt said:
Yea I dont know whats going on. When I went to restart my car after the alt fuse blows, I have to pump the pedal to prime the fuel system. Why would that be? I am going to change the fuel filter today and rent a scanner (You get all the money back). Thanks for all the help!

Pumping the pedal does not prime the fuel system (you have carbs on the brain). If pushing the gas pedal down a little ways helps it start, check and/or clean the IAC. If you have to push the gas pedal down really far, you might have too much cranking fuel.

philly_blunt · Jun 13, 2007

Well i will just add that to the list of things to check. That wouldn't be related with the alt fuse though would it? I'm pretty sure the iac does need to be replaced though because when coming to a stop, my idle jumps and and down and eventually evens out.

HISSIN50 · Jun 13, 2007

WHen coming to a stop, the idle shouldnt jump up and down.

I agree that your alternator fuse should not have a bearing on this - the car will start and run for a finite period with no alternator in the car.

chuck943 · Jun 13, 2007

trace the yellow/white wire from center of connector to alternator, it travels over to left side of engine compartment harness to a 4 wire black connector near battery junction box. Make sure it is not chaffing against metal somewhere and disconnect connector and make sure there is not alot of corrision there

philly_blunt · Jun 14, 2007

Chuck, are you talking about the alternator harness? If so, i traced that back and already replaced those wires.

Hissin, I am hoping a new IAC will fix that idle problem. This is the site that I got info on for the IAC being the culprit for this problem. http://www.muscularmustangs.com/iac.php What do you think?

chuck943 · Jun 14, 2007

I am assuming that you just replaced the harness pigtail at the alternator itself,right?
The yellow/white wire goes ito a larger harness and travels along the body rail up to the battery junction box fuse panel to the Alt fuse. Just before it gets there it goes thru another black 4 wire connector. I am thinking that some where along the way either the larger harness running along the body rail may be chaffing against metal,or there could be excessive corrision in the black connector.

Also clean the IAC and disconnect battery for about 30 minutes to reset PCM stadegies to see if this fixes you idle problem before just replacing IAC. See PCM stradegy has what is called closed throttle voltage,this voltage is what the PCM sees as idle voltage. It is normally equal to TP voltage at idle (.8 to 1.0 V)however if your battery goes dead or voltage drops dramatically this may change if it drops to say .5 volts then PCM now thinks this is where idle should be it then will try to pull idle down to this(called hunting idle) and can cause it to stall. If closed throttle voltage has dropped you have to reset the stradegy to get it back where it needs to be.

HISSIN50 · Jun 15, 2007

If all else fails, we could examine what I addressed at the end of Post 3. You could loop the sense wire (terminal A at the reg) to the alt's charge stud for a test run/diagnostics. This is a common method with retrofits anyhow (you just need to ensure your charge cable and connections are impeccable since you lose the remote sensing).

This would remove that assumed-bad section of wiring.

If ever needed, the same type of loop can be made with the stator wire (from the S-terminal at the reg plug, to the single stator wire hook up on the alt case).

Just another option.

Good luck.

philly_blunt · Jun 15, 2007

Well, I'm pretty sure its fixed for good now!!! I got the alternator tested about 6 times in a row and it passed the first two times and failed the rest. I'm assuming it was the voltage regulator. I got two alternator's in a row that were bad out of the box. thats horrible. I also bought a kit and rewired my cooling fan with an adjustable temp sensor (the guy who had it before me had it hooked up to the a/c). Well thanks to all very much and i hope this is a permanent fix! I will be starting another thread soon on how to put a/c back in the car(previous owner took it out).

oh yea, i did clean the IAC and have the battery disconnected for at least 30 min. It seemed to help it, but the problem is still there. I also pulled the CEL codes and they were : EGR below min, voltage and Thermatic sys inoperative during test. I don't have a smog pump or a/c, and the EGR is not hooked up.

philly_blunt · Jun 15, 2007

I was thinking, why would my egr not have a vac line to it? Isn't it supposed to get some vacuum source from the intake manifold?

HISSIN50 · Jun 15, 2007

Depending upon how bad of a hack job was done with the EGR removal, who knows what was done. In proper form, the EGR valve indeed has a vacuum line coming from the EGR solenoid. The solenoid receives manifold vac and divvies it up to the EGR valve when the puter tells it to.

Nice work on the alt fix. I'm glad rewiring wasnt needed - you hadn't asked about any 'shortcuts' or methods of re-wire, and I hate to do that kind of thing. But if the car was a driver and it kept crapping its pants, a work-around could have been needed.

Good luck with it.

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