TECH TIP FOR OCTOBER,1997

AT A RECENT TRADE SHOW/SEMINAR THE GUEST SPEAKER BROUGHT UP A SUBJECT WHICH CAN AND PROBABLY WILL CAUSE MANY HEADACHES FOR MECHANICS IN THE FUTURE. THE PROBLEM IS INDUCTED VOLTAGE. AS WE ALL KNOW WHEN YOU PASS CURRENT THROUGH A CONDUCTOR YOU CREATE A MAGNETIC FIELD AROUND THAT CONDUCTOR. TO ADD TO THE PROBLEM, WHEN YOU PASS A CONDUCTOR THROUGH A MAGNETIC FIELD YOU INDUCE A CURRENT INTO THE CONDUCTOR.

THIS WAS NOT OF MAJOR CONCERN IN THE PAST WHEN SYSTEMS WORKED ON VOLTS OR AT MINIMUM 1/2 VOLTS, BUT TODAY MANY CAR SYSTEMS WORK ON  AND REFERENCE MILLIVOLTS. IT IS NOW POSSIBLE FOR INDUCED VOLTAGE TO HAVE AN EFFECT ON ALL KIND OF THINGS. A CASE IN POINT, THE SPEAKER WAS TELLING US OF A PROBLEM WITH A CAR WHICH WOULDN'T RUN PROPERLY. IT WASN'T THAT IT WOULDN'T RUN AT ALL, OR WOULDN'T START AND FOR SURE, IT DIDN'T LOG ANY CODES, BUT EVERYONE WHO DROVE THE CAR SAID IT JUST DIDN'T RUN RIGHT. ON AND OFF THERE WAS WEEKS OF TIME SPENT WORKING ON , CHECKING AND THINKING ABOUT THIS PROBLEM. THE OWNER SAID IT HAD BEEN THIS WAY FOR SEVERAL MONTHS AND FINALLY PIN©POINTED THE BEGINNING AS RIGHT AFTER THE WIPER MOTOR HAD BEEN REPLACED. THINK ABOUT THIS FOR A BIT AND THE ANSWER WILL BE AT THE END OFTHE TIP.

A CUSTOMER OF OURS REPORTED A 1990 DODGE PICK-UP THAT WOULD CHARGE FOR ABOUT 5 MINUTES AND THEN SHUT DOWN ALTHOUGH THE TRUCK WOULD RUN FINE UNTIL THE BATTERY WAS DRAINED. HE CHECKED ALL THE EASY THINGS, REMOVED THE ALTERNATOR AND SENT IT TO ME. THERE WAS NOTHING WRONG WITH THE ALTERNATOR AND HE RELUCTANTLY RE-INSTALLED IT. THE FINAL ANSWER APPEARS TO BE TEMPERATURE RELATED. AFTER ABOUT 5 OR 10 MINUTES OF RUNNING THE COMPUTER WOULD HEAT UP AND THE REGULATOR SECTION WOULD LOSE GROUND. A NEW COMPUTER SOLVED THE PROBLEM.

1992-1994 SABLE & TAURUS WITH A V6 ENGINE MAY EXPERIENCE A SLOW OR NO START CONDITION EVEN THE BATTERY, ALTERNATOR AND STARTER HAVE BEEN REPLACED.

FORD/MERCURY HAVE FOUND THIS CONDITION TO BE CAUSED BY A SHORT IN THE # 33 CIRCUIT ON THE 12A581 & 14290 WIRING HARNESSES. BOTH HARNESSES RUN ACROSS THE FRONT OF THE ENGINE AND TRANSMISSION, WHERE THE TRANSMISSION HAS A SHARP EDGE WHICH, OVER TIME, WILL RUB THROUGH THE INSULATION A CAUSE A SHORT.  IF THIS CONDITION IS FOUND, REPAIR THE DAMAGE AND RE©ROUTE THE HARNESS AWAY FROM THE CASE TO PREVENT REOCCURRENCE. 1989-1992 FORD/MAZDA. THE EARLY FORD PROBE AND MAZDA MX6 MAY EXPERIENCE CONTINUOUSLY DISCHARGED BATTERIES OR COMPLETE NO STARTS CAUSED BY WATER ENTERING THE ELECTRICAL CONNECTORS AS THEY PASS IN FRONT OF THE RADIATOR AND ALMOST ANYWHERE IN THE ENGINE COMPARTMENT.

TO LOCATE THE PROBLEM IT IS NECESSARY TO DO VOLTAGE DROP TESTS ACROSS EACH CONNECTOR OR BETTER YET TO SEPARATE EACH ONE, CLEAN, AND FILL WITH DIE-ELECTRIC GREASE.

HYUNDAI REPORTS THAT 1992-1993 SONOTAS MAY BE SUBJECT TO CONTINUALLY DISCHARGED BATTERIES WHICH CAN/WILL LEAD TO A NO START. (AND WILL SHORTEN STARTER LIFE) CAUSED BY A DIODE FAILURE IN THE WIRING TO THE COOLING FAN RELAYS. IF THIS DIODE GOES OPEN THE RELAYS WILL KEEP THE FANS RUNNING FOR AS LONG AS THERE IN SUFFICIENT POWER IN THE BATTERY. SINCE THE FANS ARE SUPPOSED TO RUN FOR A PERIOD OF TIME AFTER THE CAR SHUTS OFF THE OWNER WILL NOT KNOW UNTIL THE CAR WON'T START.

THE DIODE IS LOCATED IN-LINE, BEHIND THE BATTERY IN THE ENGINE WIRING HARNESS. A SERVICE MANUAL WILL GIVE AN EXACT LOCATION. IF NECESSARY, THE DIODE IS AVAILABLE FROM HYUNDAI, PART # 91798ª33000. NOW FOR OUR POORLY RUNNING CAR. IS THE FACT THAT THE POOR RUNNING STARTED AFTER THE WIPER MOTOR WAS REPLACED SIGNIFICANT. YOU BET! WHEN THE MECHANIC WAS INSTALLING THE WIPER MOTOR HE MOVED THE WIRING LOOM, WHICH RUNS ACROSS THE FIRE WALL TO GET ACCESS TO THE TOP MOUNTING BOLT. UNFORTUNATELY HE DIDN'T PUT IT BACK AND THE ANSWER IS THAT IT WAS ALMOST ON TOP OF THE DISTRIBUTOR WHERE THE INDUCED MAGNETISM WAS CAUSING THE POOR RUNNING. THE FIX WAS TO REPOSITION THE HARNESS WHERE IT BELONGED.

ON THE SAME SUBJECT, HAVE YOU EVER WONDERED WHY THE COST CONSCIOUS CAR MANUFACTURERS WOULD USE THOSE VERY EXPENSIVE BRAIDED CHASSIS GROUNDING STRAPS INSTEAD OF CHEAPER MULTI STRANDED WIRE? THE ANSWER HAS NOTHING TO DO WITH FLEXIBILITY.