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Fan/Interior light shut on/off while braking or accelerating


magnum3672

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I haven't seen much posted specifically about this so I thought I'd document my struggles with this car.

 

Info : 2011 Ford Edge SEL 2WD with about 160,000 miles clocked

 

Background:

About a year ago I started having a few electrical hiccups and after taking it to my shop/friend he diagnosed a bad alternator. At that time it was pretty much just having trouble starting after a couple days of sitting (like a long weekend) and after the alternator replacement all was good. At that time I decided to replace the battery as well because he said it was probably on it's last legs.  After replacing both of those everything seemed fine on the car and I continued to use/abuse it pretty much daily. Then last february we went on a longer trip and the car sat for 2 weeks. Upon getting home the battery was completely dead and my charger at home couldnt/wouldn't charge it up. I took it to the store I bought it from (it was only a few months old at this point) and they were able to charge it and test it and it came back good. I put it back in the car and everything seemed to be alright for a short period.

 

As the seasons changed though I started getting weird behavior. When I started driving it to work in the morning during the surface streets driving (before I hit the highway) the blower fan and then the interior lights were flickering on and off. Added to this it would occasionally stall during idle especially during stop and go traffic. To address the stalling I replaced the throttle body myself and did the relearn process. However, after replacing the throttle body the stalling and blower/interior light flickering became worse.

 

Off I went to my mechanic friends shop. While we were there we saw a partially chewed fuel injector wire and thought that that could be part of the issue so we patched that up. On trying to leave the shop though the problems resurfaced and for once the mechanics got to see the issues first hand! We tore through the electrical and charging systems and narrowed down the issue to PROBABLY being a bad regulator signal from the PCM. Our method for going that direction was checking the charging volts via a multimeter and also seeing what the car was reporting via OBD2. The multimeter showed 15+ volts while the car was running with accessories on and the diagnosis tool was showing the cars computer was reporting at most 14.8 volts. We then checked voltages again after unplugging the alternator from the PCM/ECU.  With the alternator unplugged from the PCM and going into "default" mode (not sure if there is a technical term for this) the car seemingly has gone back to a good driving state. The blower fan has shut off and on twice but both times that was when the car threw the "check charging system" warning at the same time so I'm assuming it is related to that.

 

My next steps are to buy a refurbished and programmed PCM/ECU and throw that in, plug the alternator back into the system and see if that officially fixes my symptoms. I'm not sure if anyone else has seen something similar but please chime in on your processes and I will update once I have the new PCM installed.

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It sounds like multiple problems chasing you around. 

 I would check the alternator ground. I've seen where the coatings on an alternator, will

mess with the electrical system. Also, check the engine ground to body too.

Simple jumper wires will suffice. If you have a multi-meter put it inline with

the jumper wire in DC range and see if a voltage is present. (voltage indicated a bad ground)

Do that for both the alternator and engine grounds. Also check the Battery cables clean if necessary.

 

Next see if the power side of the fan and lights are on the same circuit (same fuse). If not then check

for a common ground on the fan/lights. (If common ground, then it is back to the engine /alternator).

 

GL 73

 

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We cleaned all of the grounds up and checked the wiring for any other corrosion and it did get marginally better after that, however it was still having issues. We actually cleaned every ground we could find and double checked for corrosion in and underneath the engine fuse box.

 

The reason we chased it down to the PCM is the system runs absolutely fine with the alternator running in "default" aka having the alternator unplugged from the PCM.

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