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Ronnie
Ronnie, ASE Certified Technician
Category: Lincoln
Satisfied Customers: 33454
Experience:  35 years as an automotive tech
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My lincoln 1999 town car keeps blowing fuse 12 in the fuse

Customer Question

my lincoln 1999 town car keeps blowing fuse 12 in the fuse box in the car
JA: Have you had any recent electrical work done on the car? Have you checked the circuit?
Customer: no electrical work done it started this morning then it blew the fuse which kills the cluster instrument and fuel pump
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: i put a new ignition switch in and its still blows fuse 12
JA: Anything else you think the mechanic should know?
Customer: no
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Lincoln Mechanic about your situation and then connect you two.
Submitted: 5 months ago.
Category: Lincoln
Expert:  Ronnie replied 5 months ago.

Hello and thank you fro your question,

If 30 amp fuse 12 for the air suspension compressor in the power distribution box repeatedly blows due to a dead short, the problem is most likely a defective air suspension compressor. To verify the short is not in the harness, unplug the air suspension compressor connector, remove the compressor relay from the power distribution box and install a jumper wire between terminals 30 and 87 in the relay box. If the fuse does not blow, the harness is OK. In most cases, the problem is due to excessive moisture in the compressor causing it to corrode. This is usually caused by leaking rear air bags allowing moisture to enter the system. To repair, if the compressor can be disassembled, cleaned it out and lubed it. In cases where it can not be disassembled, the compressor will need to be replaced. In either case, a new dryer assembly will need to be installed and any system leaks must be repaired to prevent a repeat failure.

Customer: replied 5 months ago.
its a 15 amp fuse not 30 left of the stering column inside the car
Expert:  Ronnie replied 5 months ago.

Does the engine start and run?

Customer: replied 5 months ago.
blowing (#12) which is a instrument cluster, anti theft, ignition switch, and ignition coil fuse.
Expert:  Ronnie replied 5 months ago.

Yes I know that, dose the engine start and run?

Customer: replied 5 months ago.
it turns over but does not start because 12 shuts of the fuel pump
Expert:  Ronnie replied 5 months ago.

Actually it shuts off power to the coils. I would start with taking a close look at the engine harness to each coil looking for a short to ground and if that checks okay then try unplugging one coil at a time and see if the fuse holds. See the circuit wiring diagram in the link below for reference. Copy and paste the link to your browser to open and view it.

https://dl.dropboxusercontent.com/u/104923897/Fuse%20%2312%20Jun%2018.pdf

Customer: replied 5 months ago.
unplugging one coil at a time and see if the fuse holds ? how do i do that umpludg a coil turn the ignition and see if it blows the fuse?
Expert:  Ronnie replied 5 months ago.

Your engine has coil on spark plug which means you have 8 coils, one on each spark plug. You can unplug one at a time and it will still run, before you do that take a close look at the engine harness to each one of them.

Customer: replied 5 months ago.
You can unplug one at a time and it will still run. ? it does not run the fuse blows so how can it run?
Expert:  Ronnie replied 5 months ago.

If its a failing coil unplugging one at a time will tell you which one is shorted simply by turning on the key, You do not have to start it.

Customer: replied 5 months ago.
just go through each coil unplug it turn the key to see if the fuse blows? on each coil?
Expert:  Ronnie replied 5 months ago.

Yes but before you do that take a close look at the engine harness to each coil for any signs of a short to ground. If you do not see any issue with it , then do one coil at a time.

Customer: replied 5 months ago.
ok ill go try that i have a lot of fuses so ill try each coil 1 at a time what happens next do i disconect with you or keep it open this chat?
Expert:  Ronnie replied 5 months ago.

The post remains open as long as you need me. Be sure to check the harness First.

Customer: replied 5 months ago.
ok the first coil i took of was coil for cylinder 1 left side of engine nearest the firewall i disconected it and turned the key and the fuse did not blow..
Expert:  Ronnie replied 5 months ago.

Okay then start the engine with is disconnected and see if it will start and run . If so and the fuse hold then either the harness to it is shorted or the coil is.

Customer: replied 5 months ago.
the car is running now should i go to the dealership and buy a coil or should i swap a coil and see if it works
Expert:  Ronnie replied 5 months ago.

I would try swapping the #1 coil with the #2 coil and see if the fuse blows again and if it does then the coil is bad and needs to be replaced.

Customer: replied 5 months ago.
ok it was running with the coil disconnected then it just stopped i checked the fuse and it was blown while it was ticking over
Expert:  Ronnie replied 5 months ago.

Okay then that sure point to a bad coil.

Customer: replied 5 months ago.
how do i find out which coil it is then
Expert:  Ronnie replied 5 months ago.

Did you not say it started with #1 unplugged and ran?

Did you ever look at the harness to all of the coils?

Customer: replied 5 months ago.
i did and i just replaced the 15 amp fuse in no 12 and it started up again with the coil no1 still of ..no inever checked the harness yes. what do i look for on the harness?
Expert:  Ronnie replied 5 months ago.

Your looking at the harnesses to each coil for any signs of where it may have rubbed through and touching ground. If it stay running with the #1 coil unplugged the the problem is with the coil or the harness to it.

Customer: replied 5 months ago.
ok got ..now it just stopped again with out number 1 coil on i checked the fuse it was blown, now i connected the coil back together put in a new fuse and it blew again right away..
Expert:  Ronnie replied 5 months ago.

Then I would be looking very close at the harness to that coil.

Customer: replied 5 months ago.
ok let me go look no cracks no ground as far as i can see i took of the same coil new fuse started straight up lets see if its still running in ten mins and then if it is should i go get a coil ? and do you think that could fix everything?
Expert:  Ronnie replied 5 months ago.

If the coil is shorted then yes it should . Im not convinced just yet it is. Chasing a short to ground can be a real SOB as you are finding out. Lets see what happens .

Customer: replied 5 months ago.
ok its still running its been 10 mins..
Expert:  Ronnie replied 5 months ago.

Just for the hell of it while its running go back out and pull on the engine harness in and around the other coils and see if its stays running.

Customer: replied 5 months ago.
it went of and i tried to start it up again with the new fuse and the no1 coil still didconnected and the fuse blew
Expert:  Ronnie replied 5 months ago.

Okay then you are still dealing with a short in the circuit.

Customer: replied 5 months ago.
were can it be then?
Expert:  Ronnie replied 5 months ago.

I suspect its in the circuit you working on but I can not say for sure.

Customer: replied 5 months ago.
what would you suggest?
Customer: replied 5 months ago.
how can i bypass the fuse no 12 wire it somehow?
Expert:  Ronnie replied 5 months ago.

You do not want to by pass the fuse, its blowing for a reason, you have to have a short to ground and if you by pass it you could smoke the harness. You need to locate the short.

Customer: replied 5 months ago.
i know that but were do i start back at the coils?
Expert:  Ronnie replied 5 months ago.

Back at the coil and the engine harness. Something is being over looked here.

Customer: replied 5 months ago.
i put coil1 back on took of coil 3 and it started up is this strange ?
Customer: replied 5 months ago.
now its running so its not shorting out correct? now if it runs for awhile then blows the fuse hmmm its something when the engine gets warm? going to keep it running and if it does not stop well its coil number 4 then not 3 ..right now its running with out coil number 4 i grabbed the harness moved it around nothing has stopped yey..
Customer: replied 5 months ago.
the airbag light is flashing do you think that has something to do with it?
Expert:  Ronnie replied 5 months ago.

The air bag flashing means the system is seeing a fault and should be setting a fault code for this and its not likely related to the blow fuse. Im off today but will return on Monday if you do not get this resolved before then

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