QuestionQUESTION: I have a 2002 PT Cruiser, 2.4L with 100K miles, that is causing me some frustration. The car is currently blowing the #12 fuse. I do not know what that fuse controls/feeds and where I should start checking to find the short in the wiring. I am also experiencing that the engine temperature is rising and that the cooling fan for the radiator is not coming on. And on top of that, I am unable to get the car to up-shift out of first gear. Is there a fuse/relay/sensor that I should check/replace or should I just "bite the bullet" and take the car in to have it serviced?
Thank you for any help you can offer.
ANSWER: Hi Billy,
I assume that the fuse #12 of which you speak is in the cabin fuse box, not the engine compartment fuse box. It is a 10 amp fuse that powers several relays (low speed radiator fan, high speed radiator fan, and a.c. compressor clutch relays) and also powers the transmission controller, the fuel vapor leak detection pump, and the brake/transmission shift interlock solenoid. The wire that carries the current to all these devices is light green black. The fuse being blown would explain why you have no radiator fan action, why the transmission will only run in 2nd gear, perhaps the non-function of a pollution control device called the leak detection pump solenoid and switch position sense, and finally the feature that requires you to have your foot on the brake pedal when you shift into gear from neutral or drive.
One of those relays/devices is drawing too much current and blowing the fuse. Do you have access to a volt-ohm-milliamp meter so you can see what the resistance measures downstream from the fuse as it stands now and then as it stands when you disconnect each of the relays/devices one at a time to see how the resistance increases? Other than trying to notice when the fuse blows, that meter reading approach would likely show you where the short/overdraw of current is located.
That would be the best way to go about finding the overlaoding/shorting object. I can describe where to find all these items for one at a time removal and the place to attach the meter to observe the effect.
Roland
PS Please 'rate' my answer, and where you see the question about a nomination of me to be 'volunteer of the month, consider giving an 'yes' response. Thank you
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QUESTION: If you do not mind, could you describe where I can find these items and where to place the meter to observe the effect and what the effect should be on the meter.
Thank you again for your help with this matter.
AnswerHi Billy,
Put one lead of the meter on the lower pin in the #12 fuse socket (with the fuse removed), and place the other lead on a shiny metal surface of the body or a body ground attachment point. Note the resistance. If it is above 5 ohms then that is high enough to not blow the fuse as it stands. If it is below 2 ohms, then remove:
the plug on the brake/transmission interlock solenoid which has a white 2-wire plug and seems to be located under the dash on the left side probably on the brake pedal arm or nearby.
and similarly pull the three relays in the box under the hood that I listed, one at a time.
the plug to the leak detection pump (black 4-pin/3-wire plug) located in a clamp at the fuel tank at its corner.
and finally the plug to the transmission control module.
See which of these items when pulled causes the resistance reading to rise significantly from the present near zero value. That would be the circuit/component that is causing the problem. If nothing jumps out, then we may have to try and catch it 'in the act' when the engine is running/ignition is 'on'.
If the resistance is above 5 ohms, you could try letting the engine warm up until the temp reaches the level that would call into play the low and then the high speed fans and see if either of those causes the resistance to drop below 2 ohms, and also try the defrost position which similarly will close the a/c compressor clutch relay. Some where along this chain the resistance will drop to less than 1 ohm and that is where the fuse would have blown if it were in the socket.
Please let me know what you find.
Roland
PS Thanks for the earlier rating and nomination. With this second q and a you are entitled to do it again if you feel so-moved.
