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Online Repair Manuals
Many sites offer free online repair guides; others cost money (sometimes lots of money!). Here's a list of North America sites that we''ll try to update as replies are posted. Please reply if you have a link for online repair info or to report a dead link. For owner's manuals please see Where To Find Your Car Owner's Manual Online.
Well duh, we have to plug our own site - you won't find a service manual but you will find lots of helpful owners (some of whom own factory manuals and may look up stuff for you at midnight). Go to the Forums tab and Browse by Make/Model for your vehicle. This Maintenance & Repair board is always a good bet for finding help too, especially the Got a Quick, Technical Question? discussion.
AutoZone's repair guides offer you information about your vehicle's operation and step-by-step illustrated repair instructions. Online Repair Guides
Your local public library may subscribe to an auto repair database. For example, the Seattle Public Library subscribes to the Alldata.com repair database and offers free access for their patrons (online and in the library). Other libraries subscribe to the Auto Repair Reference Center offered through EBSCO Publishing, or as in my case, Chilton's Online. You can call your local library to see if access to a database is offered or perform a net search for "Auto Repair Reference Center State" or "Chilton's online state" and substitute your locale for "state" in the search string.
Some auto manufacturers also offer free service information online. .
Hyundai is one - their Webtech page is aimed at dealers but you may be able to access it by registering. More details are available in the Hyundai Online Shop Manuals Access forum here.
Kia is another - you can register at their techinfo site and get access to lots of factory information.
American Honda's Service Express offers free Owner's Manuals starting with 2002 Honda and Acura vehicles and some specific guides that mainly focus on audio and security options. They also offer a paid subscription version of Service Express at the same link that covers all vehicles back to 1990 plus all active Technical Service Bulletins back to the early 70's (the same info that is available to your local Honda or Acura tech). (Thanks nearmsp!).
General Motors has MY GMLink. It's a source for digital owner's manuals and includes recall notices. (thanks George!).
Autoparts and Enthusiast sites:
If you are trying to install or remove an accessory, many online auto parts companies offer instructions. Crutchfield is well known for offering detailed instructions for car audio and video applications. The Install Doctor is another good site for radio installation info. Installdr.com.
MyIsuzuParts, Toyotaparts4u and H and A Accessories are a few of other sites that offer instructions on installing various parts and accessories.
Hondaautomotiveparts.com has a lot of exploded parts diagrams that can help you see how various components of your Honda fit together (thanks User777!).
WJJeeps WJJeeps has lots of repair procedures for your Jeep Grand Cherokee..
BAT Auto BAT Auto has lots of articles that may help you with your repair as well.
If you can't find free access to a manual, you can purchase access to various databases. There are lots of places to buy manuals on CD, DVD and paper - this guide tries to limit sources to those you can access with your computer. If your front axle won't go back in the splines at midnight on a Saturday, waiting for the UPS truck to arrive Monday morning with a manual isn't the greatest solution. So here's a listing of paid online sources - if you know of others, please reply and let others know about them.
Alldata DIY In addition to comprehensive diagnostic and repair information, you'll also find the latest technical service bulletins and shop hours estimates here. Shifty uses this one a lot.
(Many sites link to Alldata through their webpages, for example, the BAT link above has an affiliate link through to Alldata that helps support their webpage).
Chilton DIY. Offers detailed information you need to tackle both simple and complex auto repair jobs.
Mitchell1. Subscription online repair information geared for a single make/model.
Mitchell1 also offers a subscription service geared towards pros and the price reflects that, but a one month subscription could be useful if you are doing a major overhaul on several different makes of cars. It's called OnDemand5.
Helm offers online info for Ford and Honda/Acura owners.
Paid Manufacturer Sources: (thanks 0patience and nearmsp!):
Volvo Cars of North America
Toyota Technical Information Systems
Daimler Chrysler Tech Authority Online
American Honda A Honda/Acura information source for online manuals, wiring diagrams and the like.