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Glossary of car terminology

A/C compressor:        One part of an A/C system that separates the low side from the high side by pressurizing the refrigerant.

Alternator:      A modern generator that produces alternating current which is converted to direct current and (usually) regulated in the unit.

Codes (trouble codes):           Vehicle electronic modules can detect and store faults in the systems they control. These faults are named and given a number by auto engineers. Codes, faults and their numbers are standardized in the U.S. by law, with generic (three-digit) trouble codes common across all manufacturers. Four digit codes are specific to a manufacturer.

Coolant:          Commonly a 50/50 mixture of water and ethylene-glycol that circulates through the engine. A correct mixture is more resistant to freezing and boiling that plain water.

Climate control system:         See HVAC.

Condenser:     The part of the A/C system where hot, liquid refrigerant loses heat, usually located in front of the vehicle radiator.

Evaporator:    The part of the A/C system where liquid refrigerant boils and absorbs heat from the passenger compartment.

Firewall:          The sheet metal separating the engine compartment from the passenger compartment.

Freeze-frame: The information on a system that a module captures in a snap shot fashion at the time a trouble code is set.  This information can be useful in diagnosing a problem.

Heater core:   A metal heat radiator using tubes and fins to circulate engine coolant past an air stream heating the air. The heater core is located inside the passenger compartment in the HVAC plenum.

HVAC:            Heating-ventilating-air conditioning. The climate control system in a car or truck.

Instrument cluster:    The group of gauges and lights that inform the driver of a vehicle.

Module:          An electronic component that uses a computer program to control a system. Examples include the PCM, (powertrain control module), ABS module for anti-lock brakes, the Passive restraint module for air bag systems. A single car may have six or more modules, each communicating with the others.

Oscillation: linear back and forth motion.

Orifice:           One part of the A/C system that separates the high side from the low side. This is accomplished by forcing the high pressure liquid through a small hole where it can change state. See: A/C systems page.

Passive restraint:       Any passenger restraint that works without passenger effort. Includes air bags, automatic seat belts, seat belt pretensioners, and side air bags.

Plenum:           A chamber for air circulation and control. The HVAC plenum handles air for passenger comfort. The intake plenum handles air the goes into the engine.

Radiator:        An engine cooling system component that circulates coolant through a series of thin metal fins. It is located in front of the engine and cooled by outside air and a fan.

Serpentine belt:          The reinforced rubber belt that drives engine accessories like the alternator, power steering pump, A/C compressor, etc. Usually has a flat side and a V ribbed side. Serpentine because one belt drives all accessories by looping around and under them, using both sides to do work. Very tough, reliable and quieter than single V belts found on earlier cars.

Specs; Specifications, the manufacturer’s design tolerances, parameters and so on that are required for optimum performance. Common specs include spark plug gap, tire size, ride height, wheel alignment etc.

Thermostat:    A heat sensitive and temperature controlled valve, usually located at the top of the engine, that maintains correct engine temperature by controlling coolant flow through the radiator.

Water pump:  A belt-driven engine accessory that circulates coolant from the radiator through the engine to cool the engine.

Wheel speed: The frequency that a wheel rotates.

 This post addresses a common concern about the relationship of tire problems and alignment. They can be related, but not always directly. 

Sometimes a car or truck will pull to one side or the other. Sometimes the vehicle shakes at wheel speed. When these occur together and you can see and feel motion in the steering wheel, the most likely cause is a bad tire.  While a pull can be caused by an alignment problem, tire pulls are much more common. Combined with a shake, this is evidence of bad tires. If the shake, (called a steering nibble when it is observable as an oscillation in the steering wheel), occurs whenever driving, and not just when braking, you may be able to diagnose this yourself. Inspect the front tires. While stopped, steer the wheels so that you can see the tread clearly. If you can jack the tire off the ground, so much the better. Notice how much tread depth there is, and then roll the tire so that you can see the tread all around. Is there a place where the tread is noticeably more worn than the rest of the tire? If so, this is a place where a belt in the tire has slipped and caused a bulge. This bulging high spot gets more wear than the rest of the tire and is a dead giveaway of problems. The shake is caused by this high spot every time it hits the road. For some odd reason, tires with belt problems can pull, even when they don’t show a bulge. If you want to test this out yourself, swap the tires and wheels front to back. If the pull and wobble are gone, or changed, then you can be sure that tires were at fault. Alignment will not cause this problem, though a road test afterward, which is standard procedure with an alignment, should have tipped off the mechanic. Did you notice this before the work was done? If so, did you tell the shop about it? What was the reason you had an alignment done? Were the tires rotated at that time? (if the tires were rotated front to back, the problem tires could have been put to the front where their faults were more noticeable). There really isn’t anyplace to put blame here. The customer helps when they tell the shop all they know, but the shop needs to ask good questions too. I know this is a long-winded discussion, but actually, there are even more things that could be involved. Car repair is tricky, and your mechanic should work with you to get things right.

If you need more detail, be sure to ask a question in the comment area.

This post is a rewrite of an answer I gave to a question on another site. The problem was that a number of components, all on the dash or instrument cluster, were inoperative or had their warning light on. The vehicle was a Ford Explorer. I got to writing and didn’t stop until I had strayed some. Might be helpful for some of you with electrical issues, though.

When a vehicle has numerous codes in different systems, a low voltage condition is often the cause because modules do not do well at voltages below, say, nine volts. A low voltage condition can happen when the alternator is failing, or a battery is depleted by a draw and upon starting, the voltage is low for a period. In this condition, the PCM and other modules are testing their circuits and finding a lot of things out of spec. That is when codes are set. This may be a time to write down all codes and save freeze-frame information, if available. Then clear codes and retest or drive. However, your description includes systems that are module controlled and very sensitive, (passive restraints, i.e. air bags, and ABS), and systems that are less sensitive to resistance issues, (like rear window defroster which is just a heating grid and very basic). The backup light is controlled by the TPS, transmission shift position sensor, which is part module and part plain old lighting. So, my advice is to look for a bad ground connection. When a system loses a ground, it will try to ground the current wherever it can, (ever heard of the ‘path of least resistance’?). Often this is through another component making that component function oddly. Ford puts ground connections at several places under the hood, behind the front kick panels, (those plastic trim panels outside of the front passenger feet areas, both left and right), and in the rear quarter panel inside the car, behind the trim. These grounds use green screws with 8mm or 10mm hex heads. They are obvious because they have a bare eyelet screwed right to the body metal. Another critical ground is the frame to body strap. Since the body is rubber mounted to the frame, a dedicated ground is provided. In the old days, like twenty years ago, a corroded strap was not an unusual problem. Odd things would occur, for instance a customer would complain of flickering lights and, by the way the u-joint is making noise. What would happen is, without a ground, the body electrical would seek a ground through the driveshaft and back to the engine and generator. This current would etch the u-joint bearing surface and cause it to fail. Weird, huh? But true. Test this by running a wire from the battery negative to the body.

Sorry, but since those are such different systems you describe, each could just be bad on its own.

One other thing, has your car been struck by lightning? Probably not, as it isn’t likely to run afterward.

That was my answer, for more electrical discussion go to the chassis electrical blog heading

In the comment space below you can write your car repair question and it will get to me via the internet. Wonderful, huh?

 When I get your car or truck repair question I will answer it directly to your email. I may select your question for publication and provide an answer for all to see. If you have a car concern, it is likely that others do too, so let’s spread the word, okay?

When you ask a car question, please include this information as possible: year, make, and model of vehicle; miles on vehicle; engine and transmission info, two or four wheel drive; complete description of concern, (like when it occurs, sitting still or driving, under acceleration or coasting or braking, on turns, when cold or hot, only at startup or all the time, every time I drive or intermittant or seldom or once, and so on); previous repairs in this area. The more information the better.

Try to not get flustered. If you know any mechanics, you may have observed that they are usually pretty calm individuals. Hotheads who fly off the handle when frustrated do not last long in this business. It is too stressful. When things get tough, take a break, get some coffee or go talk to someone on a different topic. Take a deep breath, think of a fun vacation you had, then go back to the task. A few minutes away will often yield a fresh perspective or new idea and get you back on track.

Though I have many years of car repair experience, I do not know all. Where I lack information, I will call friends in the business or direct you to a source that might help. The important thing is to relax and have fun. It is probably not the end of the world. I will submit a sample question to get you started.  

 While you are thinking of your question, check out our local park at: http://www.koshkonongwi.com/mushkoseday.shtml.

walt