Expert: Roland Finston - 1/2/2012

Question
QUESTION: A 1998 Chrysler Serbring v 6 car blows the engine fuse while running. I replaced the fuse and the car started but it blowed the fuse again. Any suggestions?

ANSWER: Hi Paul,
I assume this is the Sebring Convertible, correct? If not let me know.
That fuse is probably 'overworked' in the original design of the wiring. Let me describe all the things that is does, and then you can try removing the various possible items/fuses to find out which when removed stops it from blowing and thus attend to the cause that way.
Starter: the current goes thru the starter motor relay to the starter solenoid switch which when activated causes the starter motor to operate directly off the battery. That solenoid switch on the starter motor could be faulty and you could disconnect the brown wire at the starter to take it out of the circuit. But because the fuse is blowing After you get the engine started I doubt the starter circuit is the cause.
fuel pump: the current flows thru the fuel pump relay in the box under the hood and actually then also runs the fuel pump. You could remove that relay to take it out of the circuit but then of course the engine won't run for lack of fuel.
Those two items are called into play by turning the key to start in the case of the starter, and to both 'run' and start in the case of the fuel pump. So see if the fuse still blows when they are removed. Of course the engine can't run without the fuel pump.
Then the current of fuse also goes to the ignition switch from fuse 8 in the run position and is drawn through three sections of the switch: out of fuse 11 in the dash it supplies current to the body control module, the transmission control module, and the instrument cluster. Out of a different section of switch it powers another segment of the body computer and fuse 17 which powers the airbag module. Out of a third section of the ignition switch it powers fuses 14 and 15 of the dash which in turn power the radio (14) and seat belt control module, intermittent wiper and combination flasher (all fuse 15). Also it powers fuses 9 under the hood which in turn power many relay actuation coils: low and high speed fan and a.c. clutch, and also part of the theft security system and a couple of warning lights on the cluster; and it also powers fuse 10 under hood which activates the fuel pump relay, the powertrain controlled and finally the controller for the anti-lock brake.
An amazing number of possible causes for just a 20 amp fuse 8 to blow! It might blow just from the combination of all those circuits eack of which is nonetheless fused. Or about the only thing that is powered while running that doesn't have a fuse in its circuit is the fuel pump motor.
You might try using the next larger amp fuse that will fit in the socket, which would be a 30 amp and see if that 'holds'. If not, then you would need to measure how much current the fuel pump is drawing. Also you could see whether something is called into play just when the present size fuse blows. And finally you could remove the secondary fuses one at a time and see which of them solves the problem and then focus on what that fuse powers.
Of course with an ohmmemter you can probably figure out which circuit has too low a resistance and thus find which one is overdrawing the current through fuse 8.
It will take some sleuthing, obviously, but I don't have any single answer for you.
Roland


---------- FOLLOW-UP ----------

QUESTION: Thank you for your response. It is not a convertible but will this info still work for the car or do you have any other suggestions? Again thank you for everything.

Answer
On the coupe Sebring, there are three different #8 fuses: in the engine compartment there is a fusible link (30 amp pink for power seats and power windows) a dedicated fuse (20 amp yellow for the ac condenser fan motor) and in the cabin there is a 10 amp red for the ignition switch which is for a number of items: antilock brakes, cruise control, combination meter, and many other functions. Which fuse is blowing, and do you notice when if blows what might have just been called into play when it blew?