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How to rewire power outlets to key power easily

9K views 52 replies 15 participants last post by  xoxoxoBruce 
#1 · (Edited by Moderator)
I grew tired of removing my TPMS from my under dash power outlet every time I parked my truck, and then having to fish it out from under seat to plug it back in. So I spent some time with the wiring diagram and came up with an easy way to switch the two under dash outlets to a acessory/run power (shuts off when key is off)

Picture #1
I obtained a fuse tap for mini fuses from advance auto. I used my bench grinder to narrow the male spade terminal of a solderless connector so that it would fit into the fuse box.

Picture #2
I then cut off the solderless connector that came with add on tap. Crimped on the modified male connector and installed a 7.5amp fuse to the top slot only.
I prefer to error on the side of caution -- I only use these two outlets for the TPMS reader (0.015Amps) and phone charging -- 7.5 is probably still more than I need. The circuits I am working with in the fuse box are 15 and 20 amp circuits so I could go even higher.

Picture #3
I removed the 20amp Accessory power outlet fuse in rear fuse box (fuse #46) I did my research and this fuse is used only for these two outlets. The cigarette lighter is a separate fuse and the circuit needs to be power at all times from the source because it also supplies power to operate a scan tool at the Data Link Connector, the power outlet in the rear is also a different circuit! I plugged in the fuse tap with the attached wire pointing to my right (front of truck). I then connected the male connector to the left side of the empty slot #29. (03 and 04 this is not used, 05-06 automatics will have a fuse here for the transmission control module) I chose this because it will have power in accessory AND run. Anybody with an 05-06 automatic that want to do this you will only find a tap with power on in run only - not accessory! right side of #44 or #48 or left side #??. NOTE I EDITED THIS, BECAUSE IT SHOULD BE FUSE #52 NOT #49.
Edit Note: please read post #45 for additional information


Picture #4
My TPMS reader can now stay plugged in. It comes on when I turn key to accssory/run and shuts off when I park my truck :banana -- this picture is after a somewhat longer test drive. Tires were 36 PSI when I pulled out of driveway.

Picture #5
This shows the connections superimposed onto the fusebox diagram

YES the fuse box cover still fits just fine!

WHY didn't I think of doing this before!

Next on the electrical modifications agenda
Make a plug in jumper harness that will switch DRL operation to the fog lights. Its going to require more time and a trip to the pick and pull for a 10 pin connector with wires from a trailblazer so I can make a harness that will just plug in series to our existing harness 10 pin connector -- no splicing of wires and easy to remove.
 

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#2 ·
Clever. Nice, simple solution to having to remember to disconnect plug in items.

I backfeed through either of the underdash PowerPoints for use with my Battery Tender. This mod unfortunately would preclude my being able to do this any longer. Correct?
 
#4 ·
Dang your good. I was using my plug in phone charger in one of those and was always unplugging and plugging it back in. I don't like to leave things plugged in. Don't know why, I just don't.
 
#5 ·
Great idea!
Putting that on my to do list, thanks for the info.
GM makes their outlets live all the time, our 59 Impala and HHR are like that. Our Toyota Celica and my daughters VW are all key operated. Turn off and remove key outlets have no power. Probably most cars are that way?
I guess GM have their reasons to be different. When they were actually cigarette lighters would seem logical.
 
#6 ·
I grew tired of removing my TPMS from my under dash power outlet every time I parked my truck, and then having to fish it out from under seat to plug it back in. So I spent some time with the wiring diagram and came up with an easy way to switch the two under dash outlets to a acessory/run power (shuts off when key is off)

Picture #1
I obtained a fuse tap for mini fuses from advance auto. I used my bench grinder to narrow the male spade terminal of a solderless connector so that it would fit into the fuse box.

Picture #2
I then cut off the solderless connector that came with add on tap. Crimped on the modified male connector and installed a 7.5amp fuse to the top slot only.
I prefer to error on the side of caution -- I only use these two outlets for the TPMS reader (0.015Amps) and phone charging -- 7.5 is probably still more than I need. The circuits I am working with in the fuse box are 15 and 20 amp circuits so I could go even higher.

Picture #3
I removed the 20amp Accessory power outlet fuse in rear fuse box (fuse #46) I did my research and this fuse is used only for these two outlets. The cigarette lighter is a separate fuse and the circuit needs to be power at all times from the source because it also supplies power to operate a scan tool at the Data Link Connector, the power outlet in the rear is also a different circuit! I plugged in the fuse tap with the attached wire pointing to my right (front of truck). I then connected the male connector to the left side of the empty slot #29. (03 and 04 this is not used, 05-06 automatics will have a fuse here for the transmission control module) I chose this because it will have power in accessory AND run. Anybody with an 05-06 automatic that want to do this you will only find a tap with power on in run only - not accessory! right side of #44 or #48 or left side #49.

Picture #4
My TPMS reader can now stay plugged in. It comes on when I turn key to accssory/run and shuts off when I park my truck :banana -- this picture is after a somewhat longer test drive. Tires were 36 PSI when I pulled out of driveway.

Picture #5
This shows the connections superimposed onto the fusebox diagram

YES the fuse box cover still fits just fine!

WHY didn't I think of doing this before!

Next on the electrical modifications agenda
Make a plug in jumper harness that will switch DRL operation to the fog lights. Its going to require more time and a trip to the pick and pull for a 10 pin connector with wires from a trailblazer so I can make a harness that will just plug in series to our existing harness 10 pin connector -- no splicing of wires and easy to remove.
:nerd:
Curious as to if your monitors are external or internal. I have an external set on my Harley, but not sure I would like the size of those sticking out on my truck wheels. What brand of monitoring system did you use and if external, could you show a pic.:smile2:
 
#7 ·
It is external - yes the valve caps are a little large. I did not want to go to the trouble to re-road force balance my tires with the internal ones. I might switch to that style when I replace the tires but i am good with what I have for now. I have won some trophies with these big caps - nobody really seems to notice. I don't really have a problem with the looks. I worry more about tire pressure without a spare then the looks! I also wanted them for my trip to Maggie Valley last year and didn't have much time so went the quick route.

I found myself not plugging it for short trips -- but I could just as easily pick up a screw or something on a short trip and ruin a tire as I could on a long trip. Now I can leave it plugged in and it is always there for me.

Not sure of the manufacturer - They were less than $100 on Amazon. Cannot read screen in sunlight - but hiding it under dash provides for some shade to read when driving topless.
 

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#8 ·
I can't think of why I'm want those outlets hot in acc, so it would work great for me. Just have to remember not to plug the tire pump in there.
Great solution to an ongoing pain in the butt that even the most strident must-be-stock fans can use. Thank you, Sir.
 
#11 ·
:nerd:
I think I will make that fuse box "mod" myself. With my speedo out of whack due to gear swap, I have been running with my Garmin GPS on the windshield to track MPH data. I also run with a radar detector in that other slot. So I end up pulling both "slightly" out when stopped so as to cut power to them.

This trick will avoid that need.:wink2:
 
#12 ·
Great write up! I did pretty much the same thing but used an in-line fuse with low profile 90 connectors. This allows the full amperage (most fuse taps are 10a max) which I need since I’m using it for ecm, tcm, and gauge ignition signals and some switches. The in-line fuses are also half the price of the taps at most places.
 
#15 ·
Thanks __ you are correct -- I am not sure what it actually connects to ( I have not found circuit 2218 as shown on diagram I used) I trans posed to the fuse location diagram from this one off one I will edit previous post it should be FUSE#52! circuit 300 on diagram shown
 

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#16 ·
Mini Fuses and (other) Mini Fuses

:crying:

I was hot to make this mod and thought no sweat, I've added a mini tap before. Stopped at Advanced Auto yesterday and grabbed one off the rack. Today, I had already ground down the male connector to fit and added it to my new mini tap.

Plugged in a mini 7.5 fuse and started to plug it all in where the 20 amp circuit was. Would not go in the slot.

Took a harder look and could easily see why it would not go in.........

Note the label on left box versus right box. I never knew there were multiple sizes of "mini" fuses. :banghead
 

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#18 ·
:crying:

I was hot to make this mod and thought no sweat, I've added a mini tap before. Stopped at Advanced Auto yesterday and grabbed one off the rack. Today, I had already ground down the male connector to fit and added it to my new mini tap.

Plugged in a mini 7.5 fuse and started to plug it all in where the 20 amp circuit was. Would not go in the slot.

Took a harder look and could easily see why it would not go in.........

Note the label on left box versus right box. I never knew there were multiple sizes of "mini" fuses. :banghead
Sorry, ran out of picture to post the box. Also note there are now low profile DUAL fuses. A single center inlet and outlets on each side. So three prongs, two fused circuits ONE fuse body.
What will they think of next to save a few bucks.

I hope it worked to your satisfaction after you got the correct fuse tap.
 
#27 ·
:|
I gotta get mine out to wash after the jaunt to Maggie V. Gotta get 'er done before it gets into the 90's today.

I'll try and snap a pic of my fuse box and give you the specific slots that I used. Get to the Auto Store and pick up a mini tap as shown in above posts.:smile2:
 
#29 · (Edited)
How I followed Autoprofs advice

:smile2:

Don't get confused cause you see three different fuse "taps" in this picture. Simply turn the fuse box door so you can follow the diagram on the back side of the door.

That diagram will show you exactly where fuse #46 is located, take the 7.5 amp fuse that (came with the tap package) and put it into the top slot. As he said, be sure to have the tap wire exiting to the front and then run that wire (with the "modified"/ground down to fit) male stud and plug that into the right hand side of #44.

Now, you should have "switched" power to those two outlets instead of always being "hot".:wink2:
 

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#30 ·
:smile2:

Don't get confused cause you see three different fuse "taps" in this picture. Simply turn the fuse box door so you can follow the diagram on the back side of the door.

That diagram will show you exactly where fuse #46 is located, pull that fuse out and put it into the bottom slot of fuse tap and take the 7.5 amp fuse that (came with the tap package) and put it into the top slot. As he said, be sure to have the tap wire exiting to the front and then run that wire (with the "modified"/ground down to fit) male stud and plug that into the right hand side of #44.

Now, you should have "switched" power to those two outlets instead of always being "hot".:wink2:
That's awesome for us "visual learner" types!

So just to be sure I got this, here are a couple of DIY images. If I've finally gotten it through my thick head, I'm off to the auto parts store (again)! :grin2:
 

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#36 · (Edited)
D'oh. My typo. You are correct, it's supposed to be #44 - I corrected my post. But if you look at the picture of my fuse box with the jumper installed, it is in fact on the right side of #44 (just like you have it in yours). Phew! Thought I was really losing it! :wink2:

So right now the moment I connect the fuse tap itself, the accessory outlets are hot again (without the key in the ignition). I connected the lead to the right side of #44 and they are still hot... plus the blower comes on low.

I'm at a bit of a loss.

No need to trouble yourself though, you've done all you can I think. I'll chalk it up to gremlins (ugly, UGLY car!) :grin2:

Think I'll run a line from an empty slot that's switched, #52, up to the dash. I don't relish trying to get the wires under the console, but you gotta do whatcha' gotta do.

BTW, hope you got your baby washed! They run so much better afterward, I swear! :)

Thanks so much!
 

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#37 · (Edited)
Okay... I'm an idiot, I admit it, right here, right now. :banghead

My error is on clear display in the photos of the fuse tap I posted earlier. No where is it written but I assumed (and we all know what that means) that the original 20a fuse was supposed to be put into the fuse tap... using it like an added circuit. Of course not. That's not what this is about. :nodno It's basically a jumper.

The fuse tap is only supposed to have the one, single fuse in it. Sigh.

Once I removed the 20a fuse and plugged it back in... tah da! It works exactly as you and Autoprof said it would.

Soooo, to button it up, here are a couple of photos of the mod I did on the fuse tap. Mostly followed Autoprof's advice but I went ahead and soldered the terminal and put some shrink wrap on it for good measure.

Thanks Autoprof and BlueStreak! Saved me from some back-breaking wire fishing and other miscellaneous hardships. I owe you both! :cheers
 

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#38 ·
Glad you got it figured out.
Sorry I was out with my wife after the car show today and just had a chance to log back on.

I believe step 2, I mention to install fuse into top slot only. I will edit that to bold face for anyone in the future.

Thanks to @BlueStreak and @moscooter for helping you with this modification.
 
#39 ·
Oh, it's there all right... means I have to look at the details though... and, well.

Hope you and the wife had a great time at the car show. Ours is next Saturday. Fingers crossed the sun will make it to the show as well!

Thanks again to you, BlueStreak and to moscooter as well!
 
#45 ·
UPDATE - installation method with better safety margin

@BlueStreak brought to my attention that the way it is wired the fuse tap wire itself might not be protected properly. I looked into this and the fuse tap wire is protected by IGN A fuse under the hood fuse box. Although there is nothing under the fuse box cover that the fuse tap wire could become grounded on and this is probably a little over the top BUT more of a safety margin could be gained by reversering the fuse tap.

Although I don't see how anything could happen with it wired the way it was shown - the additional safety margin is worth the few minutes it would take to reverse the leads. YOU DO NOT NEED TO RUN OUT and do this immediately or even really ever, but you never know what could happen and any additional safety margin is worth the effort.

I am sending to the attention of everyone I know of that responded and performed this modification
@moscooter, @CypherDesign, @xoxoxoBruce, @OldTownCruiser, @Daverobertson, @VI Ken, @06-SSR, @richsadams, @Sweet Tomato, @Dragon2U

Also @Administrator PLEASE edit first post next to text "picture #3" === please see post #45 for update


I removed the 20amp Accessory power outlet fuse in rear fuse box (fuse #46) I did my research and this fuse is used only for these two outlets. The cigarette lighter is a separate fuse and the circuit needs to be power at all times from the source because it also supplies power to operate a scan tool at the Data Link Connector, the power outlet in the rear is also a different circuit! I plugged in the male terminal of the fuse tap to the left side of the #46 fuse slot. You would then insert the fuse tap with the attached wire pointing right (front of truck) for all models except 05-06 automatic if you want power in the accessory and run positions (picture #1) into the empty slot #29. OR in all models insert the fuse tap with the attached wire point to the left (rear of the truck) into empty slot #48 and the outlets will have power in the run position only. (picture #2)

The fuse tap itself should be installed into the empty slot and the male terminal should be installed into the power outlet left side fuse slot.

Picture #1 Show the way to connect the fuse tap on all models except 05-06 automatics if you want power in accessory or Run (this slot is not empty on 05-06 automatics, the TCM fuse is in this slot)

Electronic device Technology Audio equipment Auto part Vehicle


Picture #2 Shows how to connect ALL model years for power in RUN position only (only option I know of for 05-06 automatics)
Notice This does not completely block the access of any other fuse!

Technology Electronic device Machine Electronics Auto part
 
#47 ·
UPDATE - installation method with better safety margin

@BlueStreak brought to my attention that the way it is wired the fuse tap wire itself might not be protected properly. I looked into this and the fuse tap wire is protected by IGN A fuse under the hood fuse box. Although there is nothing under the fuse box cover that the fuse tap wire could become grounded on and this is probably a little over the top BUT more of a safety margin could be gained by reversering the fuse tap.

Although I don't see how anything could happen with it wired the way it was shown - the additional safety margin is worth the few minutes it would take to reverse the leads. YOU DO NOT NEED TO RUN OUT and do this immediately or even really ever, but you never know what could happen and any additional safety margin is worth the effort.

I am sending to the attention of everyone I know of that responded and performed this modification
@moscooter, @CypherDesign, @xoxoxoBruce, @OldTownCruiser, @Daverobertson, @VI Ken, @06-SSR, @richsadams, @Sweet Tomato, @Dragon2U

Also @Administrator PLEASE edit first post next to text "picture #3" === please see post #45 for update


I removed the 20amp Accessory power outlet fuse in rear fuse box (fuse #46) I did my research and this fuse is used only for these two outlets. The cigarette lighter is a separate fuse and the circuit needs to be power at all times from the source because it also supplies power to operate a scan tool at the Data Link Connector, the power outlet in the rear is also a different circuit! I plugged in the male terminal of the fuse tap to the left side of the #46 fuse slot. You would then insert the fuse tap with the attached wire pointing right (front of truck) for all models except 05-06 automatic if you want power in the accessory and run positions (picture #1) into the empty slot #29. OR in all models insert the fuse tap with the attached wire point to the left (rear of the truck) into empty slot #48 and the outlets will have power in the run position only. (picture #2)

The fuse tap itself should be installed into the empty slot and the male terminal should be installed into the power outlet left side fuse slot.

Picture #1 Show the way to connect the fuse tap on all models except 05-06 automatics if you want power in accessory or Run (this slot is not empty on 05-06 automatics, the TCM fuse is in this slot)

View attachment 567361

Picture #2 Shows how to connect ALL model years for power in RUN position only (only option I know of for 05-06 automatics)
Notice This does not completely block the access of any other fuse!

View attachment 567362
:unsure:

" YOU DO NOT NEED TO RUN OUT and do this immediately or even really ever, "

I'm in the above camp, gonna take my chances cause cannot come up with a scenario that would evolve from the initial wiring change.:rolleyes:
 
#46 ·
Wow, great work! (y)

I think I mentioned somewhere that I wanted to power my dash cam via a USB plug in one of the power outlets. Of course I didn't want it to be "hot" when the R wasn't running. This tap worked exactly as advertised.

But in the end I decided to remove the tap and ran the dash cam wires directly to an accessory powered open fuse in the interior fuse block. Cleaner install and less likely it'll get unplugged by accident.

Thanks for your hard work on this (and everything else) @Autoprof, much appreciated! ?
 
#49 ·
This modification was exactly what I needed to convert to switched outlets in the dash. I did reverse the install direction to limit current in the tap cable and loads from a local fuse but still think this to be one of the most elegant improvement methods I have come across. No permanent wire cuts or re-routes. Many thanks to the originator and supporting fanatics. I did cut out one of the legs/pins from a 3 amp fuse that came with the tap kit to use at the single connection location. After cutting off the tap's crimp connector I soldered the lead to the pin of the sacrificial fuse. I applied double heat shrink over the solder joint which worked well as handle of sorts to push the pin into the appropriate fuse slot.
 
#50 ·
Just did this fix on my 05 six speed.

Fantastic and clean fix!!!!

I'm very happy with the results.

Only issue I'm confused over is my TCM fuse slot. My slot has a fuse in it but was under the impression that should only be fused in Automatic Transmission SSRs????

@Autoprof any ideas on this slot having a fuse in my six speed????
 
#51 ·
Just did this fix on my 05 six speed.

Fantastic and clean fix!!!!

I'm very happy with the results.

Only issue I'm confused over is my TCM fuse slot. My slot has a fuse in it but was under the impression that should only be fused in Automatic Transmission SSRs????

@Autoprof any ideas on this slot having a fuse in my six speed????
I am glad you found this helpful.

Regarding the TCM fuse (#29) on a 6 speed.
My guess is someone that didn't know what they were doing and the SSR had an issue - saw this empty slot in the fuse box and stuck something in it, or they removed another 10 amp fuse from someone else to visually inspect it (something I discourage - use a voltmeter or testlight) then forgot where it came from and stuck in in that slot. Either way it should no effect a thing if you remove it.The terminals are still there so that one fuse box can fit multiple models -- this is done a lot across many manufactures
I know there will be at least one more 6 speed at the Ohio chapter tech session Sunday - I will look at theirs.

Notice the attached diagram - it only goes to the TCM! (M32 is the option code for the Automatic)
Font Parallel Slope Rectangle Pattern
 
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