Compressor Update and Alternator tragicomedy

 "Often a very old man has no other proof of his long life than his age" - Seneca the Younger

 The replacement switch that turns the air compressor motor on and off arrived yesterday.  I had mentioned in a previous post that the switch currently installed has an air leak, which then lead to the compressor motor tripping the overload.

I ventured out to the shop to see if the switch that I'd ordered is the correct one, and it appears that the two are identical.  I didn't linger, because the temperature in the shop is set at 40F (4.4 C), and I could easily see my breath as the old fingers grew numb.  I was just checking the new switch vs the old one.

Looks like a very close, if not identical match.  I will almost certainly need to adjust the pressure setpoint after replacing the switch, by raising or lowering the brass cylinder, but that should be fairly simple to do.

The battery light on the Subaru came on recently as I was driving home from work.  

This light means that something has gone wrong with your car's charging system, the voltage is dropping down low enough to cause an alarm, and you are very likely running your battery down.

Advice time for when you see this on your car's console:

• If possible, shut off your headlights - they draw a lot of power.
• Turn your heating and/or cooling down to minimum - the fan draws power you might need to get home.
• Turn off your heated seats, your electric rear-window defogger, your steering wheel heater, and side-view mirror heaters.  Those all require a lot of power - all of which will be coming from your rapidly discharging battery.  

The purpose of shutting off the above items is to save the energy remaining in the battery for your engine computer and spark, so that you can extend your driving range and get home.  You will still be drawing down the battery charge, but at a much less rapid pace.

Now for the low-budget alternator troubleshooting advice.  (Do not hold me to account for any damage that may result - I am not a professional automotive electrician)

Once you get home, and with the engine still running, open the hood, and disconnect one terminal of your battery.  If the car dies immediately, that tells you - almost certainly, that your alternator isn't working.  

If the alternator were working correctly, it would have continued to provide power for the engine spark, even with the battery disconnected.  Since the engine died when the battery terminal was removed, nothing was providing power except for the battery.

Some folks say you might over-voltage your car's delicate electronics if the alternator voltage has failed high, without the battery there to buffer the output.  That theory is bullcrap, because you would not have gotten the low system voltage alarm if the alternator were putting out too much voltage!

The only reason that I'm explaining this:  I recently went through all of these steps, and maybe someday it will save you the expense of dealing with a garage or an expensive mechanic. 

In any event, the alternator on the Subaru was fried - center with cooling passages cast in to cool the windings.

Below:  There is some black melted plastic material on the case of the alternator.  Fortunately it wasn't from the electrical connector.

Now for the tragicomedy part of the story.  I went to the local Home-Gamer auto parts store (AutoZone) to see about getting a replacement.  I wanted to buy one off the shelf and get the Subaru going before bed-time.

Here were the prices:

I told the kid that I'd like to buy the cheap one.  He looked it up, and said he didn't have any in stock, but that he could get it by the following day.  I told him to forget about it, and that I'd get one from Amazon. 

Amazon also had an alternator that they could deliver to my doorstep the following day - and the pricing was quite a bit better.

I don't mind paying a premium for something that I need right now, but if you run a brick and mortar store, you should keep stuff like this on the shelf.  That's because if you are going to make me wait, I can find a less expensive alternative for the same wait.

So for one day I drove the plow truck to work, and by the time I got home, the alternator was already there.  I warmed up the shop, then went out and installed the new alternator in about 20 minutes.  

Afterwards, I took the Subie for a spin with all those electrical items turned on, and there was no "low battery voltage" light to be seen.  So far, so good!

Keep Amazon in mind next time you need a car part!