Battery, Alternator or Other. - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Kabad · 04-30-2008, 07:33 PM

Hi! great forum just joined yesterday. I owned a 1994 Porsche 911 that I sold last year, I was talked into buying a Boxster by my youngest daughter (I wasn't a very hard sell) and I can't believe how much I love this car, I like driving it more than the 911. I bought a 2000 Boxster with 60,000mi and have had no problems with the car until this spring.

I stored the car for the winter (I live in Minnesota) forgot to unhook the battery and this year when I tried to start it the battery was dead. I charged the battery and the car started up right away. I took it out on a 20 mile drive, my battery idiot light stayed on, I thought it was telling me that my battery was charging, not so. My radio died and then the car died. I had my wife meet me and jump start the car enough to get it home. I thought I just had a bad battery and bought a new one. But the red battery idiot lights stays on. I didn't drive it, I don't want to get caught on the roadside again.

Any suggestions? Do you think I need to replace my alternator? That's my guess, but it seems strange that it worked great last year but has a problem this year. Thanks.

Lil bastard · 04-30-2008, 10:14 PM

Well, there are a couple easy checks but you need a DMM (Digital Multi-meter).

The battery isn't exactly 12 volts. Each of the six cells produces somewhere in the neighborhood of 2.2 volts. If you checked the voltage between the battery posts (car OFF, battery cables disconnected) you should see somewhere between 13.2 - 13.5 volts. Since you just bought a new one, this is not likely an issue.

You can start the car and check the voltage between the battery terminals - this time, you should bget a reading of between 13.8 and 14.5 volts - this is your alternator voltage.

A bad battery can damage or even ruin an alternator. Your previous battery may have been failing long before you stored the car and caused the alternator to work harder which means that it ran hotter and/or was subject to voltage spikes as high as 45 volts which could easily damage the integral diodes which act as voltage stabilizers/regulators.

If it is the alternator, it's not difficult to swap it out. Before buying a new one, look into having your existing one rebuilt - there are lots of shops offering this at considerably lower prices than buying a new replacement. Good Luck

Kabad · 05-01-2008, 04:39 AM

Thanks for your help, if the battery light stays lit will it hurt anything on the car to drive it, except drain the battery if the alternator is not working?

Kevfra · 05-01-2008, 06:00 AM

When people say alternator they are referring to the combination of alternator and regulator. You blew the regulator which includes the diodes, and very likely your alternator is fine. The regulator is bolted onto the back of the alternator, and you can replace just the regulator for about $75. If you first buy the regulator and have it available, you can then do the job in the car and be on the road with a much shorter down time because you don't have to take the alternator to a rebuild shop. If you need part numbers let me know.

Lil bastard · 05-01-2008, 06:02 AM

Quote:

Originally Posted by Kabad

Thanks for your help, if the battery light stays lit will it hurt anything on the car to drive it, except drain the battery if the alternator is not working?

Actually, it could. First, the new battery will become old and degraded very quickly. Batteries lose their ability to accept and hold a charge by degreees with each discharge, about 5-7 total discharges is all most batteries can endure before they're through.

Also, several other much more expensive electronic components (like the DME or Alarm Control unit) are at risk from possible voltage spikes that a bad alternator can produce.

Last time I had an alternator rebuilt (Motorola), it cost me $110, you risk much more than that by not correcting the problem.

Lil bastard · 05-01-2008, 06:06 AM

Quote:

Originally Posted by Kevfra

When people say alternator they are referring to the combination of alternator and regulator. You blew the regulator which includes the diodes, and very likely your alternator is fine. The regulator is bolted onto the back of the alternator, and you can replace just the regulator for about $75. If you first buy the regulator and have it available, you can then do the job in the car and be on the road with a much shorter down time because you don't have to take the alternator to a rebuild shop. If you need part numbers let me know.

Agreed. But, if a bad battery has been working the alternator overtime for any length of time, because this would cause it to run considerably hotter, there's a good chance that the alternator bearing, and even possibly the windings were affected. Since we don't know the answer, I think he's best served by having the alternator inspected and rebuilt if necessary. Just my humble $0.02

Kabad · 05-01-2008, 08:50 AM

Quote:

Originally Posted by Kevfra

When people say alternator they are referring to the combination of alternator and regulator. You blew the regulator which includes the diodes, and very likely your alternator is fine. The regulator is bolted onto the back of the alternator, and you can replace just the regulator for about $75. If you first buy the regulator and have it available, you can then do the job in the car and be on the road with a much shorter down time because you don't have to take the alternator to a rebuild shop. If you need part numbers let me know.

Thanks! If you have a part number that would be great. I am not much of a mechanic is it hard to install? The nearest Porsche Dealer to me is about 80 miles one way from me. Do you think it would hurt the car to drive it that far?

THANKS AGAIN FOR YOUR HELP!!!

Kevfra · 05-01-2008, 01:12 PM

Drive it eighty miles that is. With no charging it won't make it, and you're just making a bad situation worse. Also if you're not much of a mechanic this isn't a DIY chore because you have to remove the belt, work in awkward positions, know what NOT to do etc., not a first timer project. For someone with decent skills it's maybe ninety minutes, but not for a first timer.

You can put yourself really at ease and buy a Autolite Import 8747875 (SKU), Manufacturer Number 15978 lifetime warrenty, to replace the entire alternator and regulator, which I suspect any shop you bring it to will require. I don't think you'd find a guy willing to just change the regulator. But if you do it's Regitar: VRB254 IB225 and you can get one from Alternators Unlimited 510-205-0860. You may be able to find one locally if you call around to alternator rebuilders.

Kevfra · 05-01-2008, 04:27 PM

You didn't mention the engine in your original message. I know the information I provided applies to the 3.2 but I can't say I know if it applies to whatever engine you have. A little research on your part should clear that up, and the phone number I gave will still be a safe bet if you decide to order something.