Wednesday, August 5, 2009

Multimeters are Cool; Used Minivans are Not

My dad is an electrical / mechanical / power-systems engineer who has taught me about volts, amps, ohms, etc. about once a year since I was a baby. He needs to keep reminding me because my knowledge of the subject fades faster than a cheap alkaline battery in a GoPro Helmet Camera.

Unlike a battery, though, which fades from overuse, my memory of electrical stuff fades from lack of use. Maybe that's what Dad was trying to prevent when he bought me a digital multimeter for my 30th birthday this year. It was apropos considering the slew of electrical problems I'd been having with my station wagon. When I replaced that lemon of a car with a less-old minivan last week I was looking forward to forgetting everything about electricity once again. I think you can see where this is going...

Today the @#$% minivan wouldn't start! At least not until I turned off the radio and the fan, took several deep breaths, and turned the key juuuust right. So I backed the car into my driveway in an easy-to-jumpstart-if-necessary position, took my multimeter out of the box for the first time, and called Pa' for my yearly electrical engineering refresher course. Here's what he said I should do to see if there's something wrong with the battery, cables, or charging system:

1. Set the multimeter to volts and measure the voltage across the battery terminals when the car is not running. It should be around 12.5. (It was.)
2. Have someone turn the key to start the car while you continue measuring the voltage. If it drops significantly below 12.5, like down to around 9, that's bad. (It didn't.)
3. Continue to measure the voltage when the car is running. It should be 14 or more to be properly charging the battery. (Mine was 13.55. That might mean the alternator [the thing that charges the battery] isn't working quite right.)
4. If the voltage is kinda low when the car is idling, rev the engine a bit and see if that brings it above 14. (I haven't tried that yet since I sent my car-starting assistant home before Dad recommended that test.)
5. Also, while the car is running, test if the battery cables are bad by putting the black (-) multimeter terminal on the bare metal of the engine and the red (+) one on the cable attaching to the (+) battery terminal. If that's lower than the voltage just across the battery terminals, there might be too much resistance in the cables. (It wasn't.)

Conclusions:

1. My battery and cables are probably ok but my alternator might be going. I hope the alternator IS bad, because if it's not there could be a harder-to-diagnose and more-expensive-to-fix problem with the electrical system, putting me in the same place I was with my old car last year when its hellish behavior began.
2. I might actually remember about electricity now, thanks to all this hands-on learning experience.
3. I will probably stall on the side of the road tomorrow.

8 comments:

Frank said...

Thank goodness for fathers! Your dad had you check for a dead battery and that the charging system is working. You didn't give much outer info. Did the instrument lights come on? Did the engine turn over?
Is there a load on the battery when the ignition is off?
Dodge starters are not the best.

cammar said...

Hi James, thanks for sharing this!

As for the minivan, you forgot a few important 'cons':
1) way worse gas milage than your escort (specially if it was a manual shift one). I was getting 32 per gallon with mine.. before it died!
2) harder to put stuff on the roof racks in windy areas.

For my needs, SWs beat minivans always.

Outdrsmn said...

My hack mechanical knowledge of these things tells me Ignition switch. The electrical part down on the bottom of the column not the key part. Or it could be a problem with the raido or fan circut and it's pulling too much juice, also verifiable at the fuse block with the mulitmeter.

James Douglass said...

Hey Dudes,

I got a new starter and that fixed the problem. Hopefully it won't recur.

Cammar- I agree that the minivan is a bit much, although mine is only a 2.4 liter so it's ok on gas. My long-term goal is to get an efficient, reliable japanese station wagon like a honda, toyota, or subaru. Manual, of course.

TonyWind said...

To my knowledge it's quite a few years that honda and toyota don't make SWs for the US market. Only Subaru and Volvo still feature SWs in their product lines. The newest Outbacks and V70s don't have an amazing fuel efficiency though. But things may change in the near future with gas prices going up and (conscientious) people becoming aware of their carbon footprint. The minivans may become extinct like the dinosaurs...

Andrew said...

To my knowledge it's quite a few years that honda and toyota don't make SWs for the US market...




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Yosep said...

I really enjoyed this post. I will definitely check back later for more informative posts from you. Thanks!

techrentals said...

Multimeter and Electrometers Rental Multimeters helps a lot to trace electrical malfunction. Too luck you have a dad who is expert on that field.