Mechanics

NO ELECTRICAL POWER UNLESS CAR IS RUN

1994 Lincoln Town Car

Electrical problem
1994 Lincoln Town Car V8 Automatic 70000 miles

I have no interior lights or powerlocks unless the engine is running. Someone told me that it may be a bad relay. I wanted to know if I can change the relay and where it may be located in the car. The car is totaly power dead and shuts down electricaly unless the ignition is running.
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Erco67
September 30, 2010.




Hi erco67,

Thank you for the donation.

Symptoms indicates a possible power supply interruption.

Check Fuse # 17 ( 10A) in underdash fuse box. Use test lamp to check if power is available at both ends of the fuse. If power is not available, you would need to check the sullpy from battery to the fuse.

You mentioned it is totally power dead, what are the other components that are not working?

KHLow2008
Oct 1, 2010.
To answer your question. Once the car is turned off. There is no power to any component. The lights don" t work, the remote control doesn" t work either. The combination door access panel doesn" t have power. Even the trunk switch doesn" t work. Everything works though once the car key is turned on the ignition.
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Tiny
Erco67
Oct 1, 2010.
I checked the fuse and it works fine. Literaly nothing is operational when the key is not turning it on. Even the headlights dont go on. Nothing at all. Its like all the electrical power is totally shut off. I don" t know if there is a relay, but the fuse is fine and even if the fuse was not, none of those components would work when the car is operational.

Tiny
Erco67
Oct 1, 2010.
Vehicle system uses 2 power supply sources, one when the ignition is OFF and another is when the ignition switch is turned ON. If the power source is missing from the circuit when ignition switch is OFF, you would not be able to operate them until you turn on the ignition switch.

With so many items not working, it definitely is a power supply fault and when checking fuses, they might look good so a test lamp or volt meter would be the best way to go about checking.

No relays are used for power suppy of these circuits.

Check the following fuses for battery voltage: Fuses might be good, but I need to know if battery voltage are available at these points to understand the location where the power supply is missing.

Fuse # 1 ( 15 A )
Fuse # 10 ( 30 A )
Fuse # 17 ( 10 A )
Fuse # 11 ( 20 A )
All above in underdash fuse box.

Fuse A ( 50 A ) in under hood ( engine compartment ) fuse box.

KHLow2008
Oct 1, 2010.
Hi. I checked all the fuses you mentioned and they are all in good shape and carry 12 V voltage on both sides. Do I have to do it when the ignition is on or off. It just doesn" t make sense that it would be the fuses, otherwsie the components would not work when the car is running if the fuses were bad. There seems to me that whatever supplies power from the battery to the lelectrical components is not working when the ignition is off. Unless I am doing it wrong. Do I have to have the ignition on or off. What else could be blocking the power source when the ignition off besides the fuses. Thank you.

Tiny
Erco67
Oct 5, 2010.
You need to test them with ignition switch turned off.

I don't think it is those fuses mentioned but I need to know if battery voltage is present at those fuses to understand the problem.

It should be the main power supply to these fuses but if all fuses have battery voltage, then the main supply is good and you have to test the power supply to the components concerned to check if any connectors are not secure.

KHLow2008
Oct 5, 2010.
Would the power supply to the components be located under the hood. Is it nextt o the battery.

Tiny
Erco67
Oct 5, 2010.
The main power supply is from there, the fuse and fusible link box.

KHLow2008
Oct 5, 2010.
Ok. With the ignition off, none of the fuses have voltage. I took out the fuses and read the ohm resistance and the fuses are all good.

Tiny
Erco67
Oct 5, 2010.
If the power supply or mainsupply when the ignition is off is bad. Can you please tell my where I can trace it in order to find where the problem is. Do I start from the battery? Thank you.

Tiny
Erco67
Oct 5, 2010.

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