Weird electrical issue

[Nathan Long]

2005 V6 Convertible.

I'm having some strange electrical issues that appear to happen more often when the weather is warm. Initially I noticed the aftermarket radio powering off and coming back on occasionally. I figured it was a radio issue. I let my sister borrow the car for a few weeks and she reported more issues such as the headlights flickering, and check charging system message on the instrument panel. Since getting the car back and driving it myself, I didn't have any issues for a couple of weeks, but then I had intermittent issues with the following:

Check Charging System, Fuel Level Low, and DTE ODO Data Error all displaying on instrument cluster.
Windows not working
Door locks not working
Radio not working
Blinkers not working
A/C not working
B1556 and U1900 showing as fault codes on OBD2

The battery is less than a year old and my OBD2 shows consistent charging from the alternator.

I checked the grounds in the engine compartment and checked the connections to the computer. No signs of corrosion.

I'm totally stumped and looking for ideas on where to start looking. Again, these issues are intermittent and don't always happen at the same time.

I tried searching for anything similar and the best answer I could come up with was replace the alternator and I'm pretty sure that's not the issue.

Any advise would be greatly appreciated.

Thanks,
Nathan

 

[redfirepearlgt]

Smart Junction Box would be the first place to look They are known for issues. Radio, headlamp control, ac control, door locks, and others you listed all go through this device. They have been known to fail due to water intrusion in that area, or just giving up due to age.

This all said, first verify that the charging system is producing correct DC voltage. More importantly check for AC ripple on the same. If the voltage is not getting properly rectified due to failed rectification circuit/filtration AC will be highly present on the charging system as well as the power distribution bus. Electronics don't like AC voltage when they rely on DC to function.

In the unlikely event that this is simply low DC voltage output, the alternators have a mechanical clutch in them that fails or starts to slip over time. This produces low DC output (though rectification is working fine) because the unit is mechanically spinning slower than the engine is driving it.

If you find water intrusion presence in the SJB area, search for this issue and how to resolve it. Plenty of topic written on this with regard to S197 Mustangs.

 

[Juice]

I would focus on the charging system error, as it is likely a bad alternator. Good possibility fixing that will fix the other issues.
What is the battery voltage with the car NOT running? Anything less than 12.5v would mean the battery is not fully charged. Yes, it may start just fine and still be more than 50% discharged.

 

[Nathan Long]

The chargi

I would focus on the charging system error, as it is likely a bad alternator. Good possibility fixing that will fix the other issues.
What is the battery voltage with the car NOT running? Anything less than 12.5v would mean the battery is not fully charged. Yes, it may start just fine and still be more than 50% discharged.

Alternator was my first thought and I almost went ahead and ordered one, but the charging system error has only happened once for me and once for my sister. The last time I drove the car, I got no error but many electrical issues. In thinking it might be the alternator, I used torque to monitor the voltage and it was constant ~14.3v. I don't recall the battery voltage when not running, but it wasn't less than 12v.

Smart Junction Box would be the first place to look They are known for issues. Radio, headlamp control, ac control, door locks, and others you listed all go through this device. They have been known to fail due to water intrusion in that area, or just giving up due to age.

This all said, first verify that the charging system is producing correct DC voltage. More importantly check for AC ripple on the same. If the voltage is not getting properly rectified due to failed rectification circuit/filtration AC will be highly present on the charging system as well as the power distribution bus. Electronics don't like AC voltage when they rely on DC to function.

In the unlikely event that this is simply low DC voltage output, the alternators have a mechanical clutch in them that fails or starts to slip over time. This produces low DC output (though rectification is working fine) because the unit is mechanically spinning slower than the engine is driving it.

If you find water intrusion presence in the SJB area, search for this issue and how to resolve it. Plenty of topic written on this with regard to S197 Mustangs.

I'm leaning toward the SJB. The PO let her sit out for a long time and the cowl drain clogged and I'm almost certain the passenger footwell was full of water. I've had it over a year and there is still a musty smell. I'll see if I can take a look at the SJB this weekend.

 

[Juice]

AC ripple will not show on Torque. Computers dont like AC.
Im sure when the charging system warning popped, the PCM was seeing voltage outside of the normal range.

 

[DieHarder]

The chargi

Alternator was my first thought and I almost went ahead and ordered one, but the charging system error has only happened once for me and once for my sister. The last time I drove the car, I got no error but many electrical issues. In thinking it might be the alternator, I used torque to monitor the voltage and it was constant ~14.3v. I don't recall the battery voltage when not running, but it wasn't less than 12v.

I'm leaning toward the SJB. The PO let her sit out for a long time and the cowl drain clogged and I'm almost certain the passenger footwell was full of water. I've had it over a year and there is still a musty smell. I'll see if I can take a look at the SJB this weekend.

Intermittent electrical issues are the worst.... I'd rather have a circuit completely fail. As redfirepearlgt says start by pulling the SJB and check for corrosion. While you're at it if you smell musty carpet odors it would be a good idea to pull them and check the floor pans for rust.

14.3v out of the alternator is fine. However, you might want to take a VOM and check for voltage drops in the engine bay. Check from the body of the alternator to other points on the engine (running) and especially from the alternator to the main ground on the passenger strut tower. If you see a voltage reading (esp 1v/greater) your grounds need work.

The only additional things I'd check are grounds in the cabin and pull/re-seat fuses. I've had symptoms similar to yours which turned out to be the grounds. If you have floating grounds there may not be enough potential to operate systems properly (i.e. You may have 12v but if your grounds aren't at the same ground potential the voltage difference may be lower instead of the 12v circuits need to operate).

 

[Nathan Long]

I pulled the SJB this past weekend. Sure enough, after getting a good bit of rain last week, the box had some water on it. The cowl drains are clean, so I'm not sure where the water is coming from.

Fortunately, the corrosion wasn't bad. It looked as if it was just where the fuses and a relay connect. I took the box completely apart and cleaned all of the corrosion off. I put it back together and when I re-installed it, I created a water barrier with a gallon freezer bag and some duct tape. I have driven it twice this week in the rain and all is well so far.

Now, I've got to figure out where the water is coming from. Any ideas on what in that area would leak besides the cowl drains being clogged? I don't think its the top leaking.

 

[redfirepearlgt]

There was something at one time that water intrusion could also be coming from the antenna cable where it passe through the fender or firewall into the vehicle. I'm going back a long way on memory here but seem to remember there being a tech bulletin or maybe just a good write up on where and what to do to resolve that issue. Probably easy to find if you google it or search the site.

Glad you found the issue. 99 times out of 100 when you have multiple issues like that you need to find the common link between them. The SJB was that device in this case. Had you been having issues with AC ripple on the main voltage bus, you would have likely had a wider more erratic list of problems that dealt more with drive ability than accessory issues. But it is a quick easy check where as the the SJB is a bit harder to get to. Sometimes even knowing that it pays to go after the "low hanging fruit" so to speak first even though the likelihood is much lower than the more obvious but more difficult to get to.

Good job.