I was just wondering if I was stupid to replace a well functioning alternator: My husband has a 94 Dodge Dakota truck with 99,000 miles on it and a dead battery. I jumped it and brought it to the repair shop. They put in a new battery but said they were getting low readings when the AC and lights were on, making them think it was either a bad alternator or an electrical problem. I agreed to have them put in a new alternator, but the problem was still there and they told me I needed to go to another shop that had the right equipment to better diagnose it. I had a choice about putting the old alternator back in, or keeping the new one and I told them to keep the new one in. It gave the same low readings as the old one. The next shop told me there was no problem at all and that all their readings said it was working great. I'm sure my husband thinks I was dumb for getting the alternator (although he has not said so... ), but I figured he wants to keep the truck for several more years, and maybe it wasn't a bad idea. What do you think?

To some, preventive maintenance is a waste of time and money. Their attitude is, "if in aint broke, don't fix it." From a preventive maintenance point of view, you were "in the zone" for replacing it. Alternatior bearings and brushes often need replacing between 75,000 and 150,000 miles. I'm a preventive maintenance type of guy, so I don't fault what you did, especially if you plan on keeping the truck.

You shouldn't be so gullable especially these mechanics at the shops will try to sell you any parts they want to sell you to increase their profit. Alternators are functional until you see the warning light on your instrument panel.

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Originally Posted by hakunah

You shouldn't be so gullable especially these mechanics at the shops will try to sell you any parts they want to sell you to increase their profit. Alternators are functional until you see the warning light on your instrument panel.

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That's not exactly correct.

Most vehicle charging system lights are only going to come on if there is a low charge rate. You could have a poor charging system without a low charge rate. Say for example, if the diodes failed, the charging wave form would be wrong, but the charge rate would still be there. The battery would not like the "taste" of that A/C wave form. Another concern would be if it is over charging. That could damage the battery quicker, too.
The first shop indicated that further diagnosis was in order and she decided to keep the alternator. Being cautious isn't the same as being gullible.