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Discussion Starter #21
Here's some info on the tsb:


However I don't think any of that wiring does anything for the cooling system.

Thinking this is why people are telling you to check your O2 sensor. Realize it's for an st, but there's a lot of similarities. Maybe worth checking fuse 32 at least.

Thanks for sharing this. Here's the latest:
  • Tested fan motor by applying 12v direct to the fan (bypassing the module). Fan comes on fine.
  • Disconnected wire harness from module, turned on car and turned on AC. Hooked up voltmeter and no voltage measured on the harness.
  • Swapped relays (even though bench tested ok), repeated above test. No difference
My conclusion is that, as best I can diagnose with the tools I have, the electrical path from the relay all the way to the fan motor seems good, which would imply that the issue is somewhere between the ECT (which is brand new) or the AC sensor, the PCM and the relay itself.

I will check the O2 sensor fuse just for the heck of it...
 

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Discussion Starter #22
Well, I'll be darned...fuse 32 is blown...stay tuned...
 

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Discussion Starter #23
Well, I'll be darned...fuse 32 is blown...stay tuned...
Wow...replaced fuse 32...and now the fan's working! I don't see any shorts on either the upper or lower O2 sensor lines. I will drive it a bit over the next couple of days and see if the fuse holds up or not. Thanks for the tip!
 

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Nice work man! You did some really good troubleshooting to get to this point, having multiple different things on one fuse leads to some very illogical symptoms.

Hope the cause of the blown fuse is easy to figure out.
 

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Discussion Starter #25
Nice work man! You did some really good troubleshooting to get to this point, having multiple different things on one fuse leads to some very illogical symptoms.

Hope the cause of the blown fuse is easy to figure out.
So...not a good update: I did an idle run-up test test get engine coolant temp to the point where the fan should kick in...and it didn't (recall that the ECT sensor is brand new). Turned on the A/C, still no fan. Checked fuse 32, still good...back to the drawing board...
 

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Discussion Starter #27
The fuse blew for a reason. It may not be blown now, but something caused it. You'll have to track it down.
Yep, for sure...my initial visual inspection of the lines from the sensors to the harness did not turn up any abrasion or obvious wear on the insulation, so it looks like it will be a bit more challenging...
 

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Yep, for sure...my initial visual inspection of the lines from the sensors to the harness did not turn up any abrasion or obvious wear on the insulation, so it looks like it will be a bit more challenging...
And this is where a multimeter comes in handy. In order to have a short, power must be reaching ground. Disconnect the battery. Set multimeter to ohms. Put one lead of multimeter on a ground. Probe end off connector at the power point and pull and twist connector to see if it changes from infinity to zero.
 

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Discussion Starter #29
So, I took it to the shop and the tech found a blown megafuse (photo). When he jumpered the fuse, the fan worked and the current draw across this fuse was 17A, so seems looking good. I have no wiring diagrams/manuals for the car, so I'm curious as to what this wire is for and why it would fix my fan?
306663
 

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Discussion Starter #30
So, I took it to the shop and the tech found a blown megafuse (photo). When he jumpered the fuse, the fan worked and the current draw across this fuse was 17A, so seems looking good. I have no wiring diagrams/manuals for the car, so I'm curious as to what this wire is for and why it would fix my fan? View attachment 306663
Ok, I'll answer my own question...:) This is power to the cooling fan relay (Megafuse 8), so that makes sense!
 

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Ok, I'll answer my own question...:) This is power to the cooling fan relay (Megafuse 8), so that makes sense!
Glad you got it fixed. Thanks for the update. I'm curious as to why it would blow. Has to be a short or an accidental grounding from prior work.
 

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Discussion Starter #33
We got the car back from the shop, and so far, so good. It's a really hot day, so perfect day to test the system. I'm curious as to what would cause that megafuse to blow, but of course you can't really say nor can the shop really do anything other than measure current across the new fuse, which all seems good. Hopefully, this is the end of the saga.
 

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Discussion Starter #34
...and you won't believe this: about an hour and a half ago, my daughter called me stranded at a busy intersection blocking traffic with a "Starting System Fault" indicator. This wonderful situation prevents you from putting the car in neutral and pushing it aside. After trying, along with the help of two police officers, everything we could think of to get it in neutral, we had given up and were waiting on AAA. I googled this issue and read something about the chip key going bad. I sent my son home to get the other key. I put it in the ignition and the car fired right up. Fortunately, we don't live far from where this occurred, so I got the car home safely. (the fan is working great at all speeds, btw) I shut down and a few minutes later, went back out to try and start it--no joy. Same Starting System Fault message. No OBD II codes, either. Then I found this post. Exact same year and model as my Focus, and what do you know? Mega fuse 9 was the culprit, which just so happens to be next to the newly replaced mega fuse 8. The tech is very good and I trust him, so I really doubt he did anything to damage the other mega fuse (which would seem very hard to damage), but I'm wondering if the restoration of fuse 8 and the fan circuit may have led to something happening with fuse 9. 50 amps is a heck of a lot of current, and electrical issues are not my strong suit, so I'm kind of at a loss as to what's going on here. Of course my plan is for the tech to look at it again, but right now, I cannot even start the car, so if anyone has ever seen this or any other issues with the high current battery junction box, I'd love to learn more. Even better, I have a 2014 Focus for sale, cheap. :mad:
 

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Discussion Starter #36
Mega fuse 9 replaced, so far so good...hoping this is it for issues for a while....apparently when the tech was investigating this issue, he was able to start the car by shaking the wiring harness going into the mega fuse block. He kept the old fuse #9 for me and it rattles when you shake it...not good at all...
 

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I'd be suspecting the heat from issue on fan fuse messing up that area of the fuse panel. Maybe the 50 amp fuse needs to be moved off the panel and somewhat remote. Had that issue on a Contour fuse panel once. moving the problem one that got hot quit blowing ones next to it physically.
 
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