TECH TIP FOR FEBRUARY, 1998

WE ARE ATTEMPTING TO GET OUR ACCOUNTS RECEIVABLE IN ORDER. IT SEEMS THAT WE HAVE BEEN ACCUMULATING ERRORS AND INCONSISTENCIES FOR SOME TIME NOW AND I HAVE FINALLY ARRANGED WITH MY ACCOUNTANT'S OFFICE TO DO SOMETHING ABOUT IT. IF YOU FEEL THAT THERE IS ANYTHING WRONG OR STRANGE ABOUT YOUR ACCOUNT, PLEASE LET ME KNOW THE DETAILS AND I WILL GIVE IT TO THE ACCOUNTANT TO LOOK AFTER. I PROMISE I WILL NOT DO IT MYSELF!

LAST WEEK A CUSTOMER REQUESTED AN ALTERNATOR FOR A 1992 CROWN VICTORIA, WITH A 4.6L ENGINE. THEY LATER RETURNED TO ALTERNATOR SAYING THAT THEY HAD FOUND IN INTERMITTENT OPEN IN THE FUSED IGNITION CIRCUIT OF THE WIRING. COMMON KNOWLEDGE AND THEIR WIRING DIAGRAM BOOK SAID THAT THE CIRCUIT SHOULD COME THROUGH THE FIREWALL ON THE LEFT (DRIVER'S) SIDE OF THE CAR, BUT AFTER SPENDING SOME TIME LOOKING, THEY REFERRED TO A WIRING DIAGRAM FOR A 1993 MODEL, AND FOUND THE SUSPECT CIRCUIT IN A FUSE BLOCK BEHIND THE GLOVE BOX ON THE RIGHT SIDE OF THE CAR.

INTERSTATE BATTERIES PUTS OUT A NEWSLETTER AND IT USUALLY INCLUDES A TECH TIP OF SOME KIND. THE ONE I JUST READ IS NEAR & DEAR TO MY HEART BECAUSE IT COVERS VOLTAGE DROP ACROSS THE GROUND CIRCUIT. TAKING AWAY ALL THE VERBIAGE GIVES THE FOLLOWING FACT. ON A THREE-WIRE TPS (THROTTLE POSITIONING SENSOR). ONE WIRE IS THE 5.00 VOLT REFERENCE WIRE, THE SECOND IS THE RETURN TO THE COMPUTER AND THE THIRD IS THE GROUND. IF THE SENSOR REQUIRES 300 MILLI-AMPS FOR PROPER OPERATION, THEN A VOLTAGE DROP OF .400 OHMS (400 MILLI-OHMS) WILL PREVENT THE SENSOR FROM OPERATING AT ALL. IN FACT, A VOLTAGE DROP OF AS LITTLE AS .050 VOLTS WILL AFFECT THE DRIVEABILITY OF MOST CARS.

FROM THE iatn COMES:

1) 1998 LINCOLN MKVII WITH DIGITAL DASH HAS A SPEEDO THAT READS 2- 80 MPH WITHOUT THE CAR MOVING, THE FUEL GAUGE READS FULL OR EMPTY WITHOUT REGARD TO HOW MUCH FUEL IS IN THE CAR, AND INTERMITTENTLY THE HEADLIGHTS WILL STAY ON FOR UP TO AN HOUR AFTER THE CAR IS SHUT OFF. THE CAR IS LOADED AND EQUIPPED WITH THE TWILIGHT SENTINEL SYSTEM. THE CAR HAS BEEN TOWED IN TWICE FOR "NO STARTS" BUT ONCE AT THE SHOP IT WILL START AND OTHER PROBLEMS APPEAR.

"FIX" THE "NO START" PROBLEM WAS THE FUEL PUMP RELAY, THE BALANCE OF THE ELECTRICAL PROBLEMS WERE RELATED TO TWO LEAKING DIODES IN THE ALTERNATOR AND A REBUILT ALTERNATOR SOLVED THE PROBLEM.

"EDITORS NOTE" IN AND OLDER MODEL CAR WITHOUT THE EXTENSIVE ELECTRONICS THE LEAKING DIODES WOULD NOT HAVE CAUSED AS MUCH TROUBLE. AS THE ALTERNATOR WOULD HAVE CHARGED AT THE CORRECT VOLTAGE AND AMPERAGE BUT WOULD HAVE CAUSED THE BATTERY TO GO FLAT AFTER AN EXTENDED PERIOD OF SITTING. 

2) 1991 CADILLAC SEVILLE WITH A BATTERY THAT DOES FLAT WHEN SITTING. CHECKING PARASITIC DRAW SHOWS 220ma AT THE ALTERNATOR. CHANGING THE ALTERNATOR DID NOT CORRECT THE PROBLEM. FURTHER TESTING SHOWS 2 VOLTS ON THE "L" TERMINAL KOEO. GROUNDING THE ALTERNATOR OR REMOVING THE D©15 WIRE FROM THE BCM WILL MAKE THE DRAW GO AWAY. INSTALLATION OF ANOTHER BCM ALSO HAS NOT CORRECTED THE PROBLEM.

"FIX" THE PROBLEM WAS A LEAKING DIODE IN THE TRUNK PULL-DOWN SWITCH WHICH WAS WAKING UP THE BCM THROUGH THE "TRUNK AJAR" CIRCUIT.

3) 1994 LINCOLN CONTINENTAL WHERE THE BATTERY GOES FLAT AFTER THE CAR HAS SAT FOR 3-4 DAYS. TOTAL PARASITIC DRAW WHEN CHECKED WITH EVERYTHING OFF IS 180ma.

"FIX" THE DRAW WAS IN THE JBL SOUND SYSTEM. DISCONNECTING THE SUB WOOFER IN THE TRUNK ELIMINATED THE PROBLEM. EVIDENTIALLY THE AMPLIFIER WHICH WAS LIVE WIRED ON A SEPARATE WIRE DIRECT FROM THE BATTERY WAS TURNING THE REST OF THE SYSTEM ON.

FROM THE "SAY WHAT!" FILE COMES:

"COMPUTERS IN THE FUTURE MAY WEIGH NO MORE THAN 1.5 TONS." POPULAR MECHANICS  1949.

"I THNK THERE IS A WORLD MARKET FOR MAYBE 5 COMPUTERS." THOMAS WATSON, CHAIRMAN IBM 1943

"THERE IS NO REASON THAT ANYONE WOULD WANT A COMPUTER IN THEIR HOME." KEN OLSEN, FOUNDER, PRESIDENT & COE DIGITAL EQUIPMENT 1947

AND FINALLY "EVERYTHING THAT CAN BE INVENTED, HAS BEEN INVENTED." CHARLES H. DUELL, COMMISSIONER, U.S. OFFICE OF PATENTS, 1899.... HE THEN CLOSED THE OFFICE AND SENT EVERYONE HOME.