This one has me stumped. I drive a 1999 Ford F250 Super Duty 4x4, AT, 5.4L. I have fixed a few mechanical issues with it, now I have an electrical issue. I do not know when it began, but I noticed it two days ago. Here goes:

I drove the truck on a long trip in the rain, and parked it over night. I noticed when I was driving in my wiper motor was not working properly on low settings (stopping and pausing), but worked fine on the highest 2 settings. No big deal because I knew it was doing this before the rainy trip. The next morning I was planning on doing some work to my heater, but realized my battery was dead. This was the first time my battery died since replacing my alternator. Haven’t had a charging issue since. I noticed my wipers were not returned to home position. Knowing I may need to replace the wiper motor, I thought that may have drained the battery (yes, I was hoping). So I put the battery charger on and let it charge over night. Oddly enough, the next day the wipers were working properly (great!). I left it parked again over night and realized the battery had died again. This time I had to look for 'another reason'. I found that my heater was left on from when I was testing to see if the heater was magically working again like the wipers (heater was still not working BTW). I charged it again, and realized the blower would run with the key in the off position. I also found out the turn signals (not hazard lights, these always work fine) would work with the key in the off position. I knew this was a problem so we took the dash apart to start troubleshooting the ignition switch. Traced some diagrams back to relay under the dash that controls the turn signals and hazards. We pulled the relay and checked voltages in certain key positions. Everything seemed correct. So next thing we did was tried to troubleshoot the relay. I am not 100% sure if the relay is bad or good, but I want to describe what is happening during our tests for a helping hand.

What we are seeing:
With the key on (12v on the relay ignition terminal) or off (0v on relay ignition terminal), the 12V b+ battery terminal on the relay has to have power at all times for the relay to work (whether its the turn signals or hazards you are testing).

With the key off and the blower control in certain positions (unlike this morning the blower seems to not be running at this time), we get different action from the turn signals. In some positions the signals work fine, in other positions the turn signals will only flash one time, in some positions they do not work at all (as they should). We checked the voltages with the relay out and blower control dial in certain positions..... 1.5v... 3.3v on the ignition terminal on the flasher relay...

I don't know what to think. Anyone seen this or have any suggestions?

 

Sounds like the windshield leaking issue to me, do a search and you'll find all sorts of info on this problem.

 

We found some info on google about a leaking windhsield, but I didn't see any wet spots on the vehicle after we took it apart. Where should I look for a water damage and what components? Thanks for the info.

 

The water was getting into the under-dash fuse box and cross-connecting circuits.

 

I've got the fuse box and gem out now. Going to go ahead and clean the hazard and multifunction switch while I'm at it. Hopefully that will do it. Would love to get my heater working, but that another issue at this point.