Rear defroster and heated mirrors do not work?

Tiny
PPRINCE72
  • MEMBER
  • 2011 FORD F-150
  • 3.5L
  • 6 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
My rear defroster and heated mirrors don't work. The light on the switch doesn't come on.
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Sunday, November 20th, 2022 AT 9:24 PM

8 Replies

Tiny
PPRINCE72
  • MEMBER
Note: fuse 15 has no power to it.
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Sunday, November 20th, 2022 AT 10:00 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm not sure where fuse 15 is, but I believe you meant fuse 56 which is a 15-amp fuse. If that is incorrect, let me know.

Now, if you have power at all fuses except 56, the problem either is the relay isn't being actuated due to a power or ground issue or there is a splice in the wiring to the fuse which may have failed.

Here is what I need you to do. Take a look at the schematic you sent, and I attached below. Remove the relay. Once the relay is removed, check connector pins 1 and 3 for battery voltage. With the key on, pin 1 will have power. Pin 3 will be hot at all times.

If both have power, the next thing to check is pin 2 for a ground path when the defroster is turned on. If there is no ground, the relay will not work, and power won't be sent.

If there is ground, as a test, take a jumper wire and jump pins 3 and 5. That should turn on the defroster by manually bypassing the relay. When you do this, confirm if there is power to fuse 56. If there still isn't, we need to check the splice.

If there is no ground, we have an issue with the defroster module.

Let me know if this helps or if you have questions. Also, here is a link you may find helpful and of interest:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find.

Joe

Note: I attached three pics below all from the same page. I did this so they are readable, and you can follow them. I have arrows pointing to the power flow and highlighted areas of interest.
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Monday, November 21st, 2022 AT 8:03 PM
Tiny
PPRINCE72
  • MEMBER
Hi Joe, the 15 is the F56 fuse that has no power to it. Pin 1 and 3 have power and pin 5 is grounded. The question I have now is testing them. I couldn't find my good testing light and used an old one. I had tester on battery positive and touched pin 2 and could hear a small solenoid click each touch and then it stopped clicking? I found my good tester and the pin 2 when tester on positive it shows a very small green flashing light in it not the bright green when on a ground. I don't know if it means anything.
The relay for defroster is one of 10 in the box so I just switched them. The 15-amp fuse still has no power. I didn't get to the jumper wire but will do that tomorrow.
What and where is the defroster module? What do they cost? If I end up trying to find the splice, would it be under the fuse-relay box? I'll do the jumper wire but I'm just curious about the other possibilities.
The attached is a picture of the air ride system it has and wiring like that scares me but just throwing it out for knowledge. I've only had the truck for 3 weeks.
Thanks for everything now go have a drink of your preferred beverage.
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Tuesday, November 22nd, 2022 AT 3:12 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The wiring in the pic doesn't appear to be factory. Is this something that was added? Also, when you check the ground, do you mean the test light bulb was dim and flashing? Was it a steady flashing or did it seem like it could be a poor connection?

Let me know.

Joe
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Tuesday, November 22nd, 2022 AT 6:50 PM
Tiny
PPRINCE72
  • MEMBER
No, not an OEM it's for an air ride system which works great but if you zoom in on the picture it has one red wire and one fusible link not attached and asked Ford dealership, I bought it from, and shop mechanic said the did some rewire.
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Tuesday, November 22nd, 2022 AT 7:55 PM
Tiny
PPRINCE72
  • MEMBER
Sorry hit send, rewiring and everything was fine and probably is just mention if as last resort.
My test light when put on battery positive and turns bright red showing power and touch ground it shows bright green and the pin 2 showed a constant tiny green flashing not dim but different area on the bulb which is only one bulb total, no idea what that means and didn't know it could even do it.
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Tuesday, November 22nd, 2022 AT 8:19 PM
Tiny
PPRINCE72
  • MEMBER
Joe, I did the jumper wire (paperclip) and no light on the rear defroster but on the paperclip when touching I saw a small spark less than a static spark. I put a video showing the small green flashing light. Let me know what you recommend next.
Thanks again
Phil
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Wednesday, November 23rd, 2022 AT 12:06 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm not familiar with your test light, but it appears that you are receiving a very weak ground. Now we need to determine if the problem is at the module, the grid, or if we simply have a wiring issue.

So, disconnect the EMTC (electronic manual temperature control) module and check for continuity in the wire. If it checks good, with the module still disconnected, check the continuity between the module and the white wire with an orange tracer at the window grid connector.

If the wiring is good, go to the grid connector, and confirm continuity between the white/orange wire on the grid and ground. If that is good, suspect the module.

I need to know two things. First, does the vehicle have factory navigation? Also, is the rear window a slider? If it is a slider, check the connectors at the grid to make sure they are not damaged. I'm starting to see them fail/break on the window grid connector pins.

Let me know so I can get you the correct location of the module.

Take care and I hope you have a good Thanksgiving.

Take care,

Joe
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Wednesday, November 23rd, 2022 AT 8:22 PM

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