Dual-zone climate control is blowing hot and cold

March 21, 2009/Steve Tackett

MOTOR MATTERS ASK THE AUTO DOCTOR BY JUNIOR DAMATO

Dear Doctor: I have a 2000 Cadillac Eldorado with dual-zone climate control. When I turn on the a/c the front outlets on one side blow hot while the other side blows cold. The same thing happens when I turn on the heat. Any suggestions? Ron
Dear Ron: The most common fault on this car is a faulty blend door actuator motor. You can check the fault codes with a good scan tool and it will lead you right to the source of the problem.
Dear Doctor: I own a 1998 Ford Expedition 5.4L V-8. There is a problem with blowing a fuse when I push the overdrive button while driving. If I push the button while in park the fuse does not blow. The mechanic said there is a short in the steering column. What do you think? Chris
Dear Chris: I would disconnect the overdrive connection at the transmission and road-test the truck to verify the problem. There could be a short in either the steering column or the overdrive circuit in the transmission. You will need to look at the wiring diagram and follow the wires.
Dear Doctor: I recently purchased a 2001 Pontiac Grand Am for my granddaughter and would like to obtain the owner’s manual. I have been unable to locate one. Where can I purchase one? Arthur
Dear Arthur: Your best bets would be to go online and search for Helms Repair Manuals or to check the local auto salvage yards.
Dear Doctor: I own a 2001 Chrysler Town & Country minivan with 54,000 miles. The owner’s manual suggests checking the timing belt at 60,000 miles. The dealer says at 70,000 miles. How long will the timing belt last and what is the replacement cost? Jim
Dear Jim: First make sure the minivan has a timing belt and not a timing chain. Second, expect to pay four hours of labor plus the parts. I like to see 5 years or 60,000 miles on the majority of engines, unless otherwise required. Some manufactures require timing belt replacement at 30,000 miles.
Dear Doctor: I own a 1975 Nissan 280Z that will act up in the hot weather of 90-plus degrees. It will just shut off. Do you have any thoughts? Joseph
Dear Joseph: If there are no trouble fault codes in the computer, then a few simple tests will point the technician in the right direction. This will require a fuel pressure tester and spark tester. Once the problem is located — either spark or fuel — the technician can concentrate in that area of service.
Dear Doctor: Sometimes my 1999 Mazda 626 will not restart hot for up to and hour. Sometimes it restarts, but runs rough. The computer does not show any fault codes. What do you thing? Al
Dear Al: You need to treat this like any other hard-start or no-start condition. On this car a scan tool would be of great help. When the engine does not start the scan tool should look at all the sensor information, including engine coolant temperature, crank sensor and mass air flow readings. Fuel pressure and spark are also critical.
Dear Doctor: My 1996 Chevy Tahoe with 177,000 miles idles well warm or cold, but intermittently experiences hesitation, won’t accelerate, and the occasional pop, which is worse in damp weather. I’ve replaced plugs, wires, cap, coil, rotor and the injectors were replaced three years ago. I’ve even tried injector cleaner. It starts easily and cruises fine at all speeds. I’ve tested O2 sensors and all are good. Frank
Dear Frank: Before any parts are replaced a full engine performance test needs to be performed. You can subscribe to alldata.com and get more information on your vehicle than you could ever imagine. I have seen catalytic converters, oxygen sensors, low fuel pressure, dirty injectors, and distributors out of phase, just to mention a few faults on this model.

Junior Damato is an ASE-certified Master Technician.

E-mail questions to info@motormatters.biz

Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347

Listen to Junior online at www.1460wxbr.com Saturdays from 7 a.m. to 10 a.m. eastern time.

Copyright, Motor Matters, 2009