Chevy Electrical Puzzle

[jerryg]

Remove negative battery cable put amp meter leads 1 on battery and 1 on cable will show amps being pulled from battery if less than 1/2 amp battery is bad or not getting recharged.
If 1 amp or more disconnect amp meter and remove wires from alternator reconnect amp meter and check for amp draw (discharge). This tell if alternator is discharging battery. You should not get a amp draw reading on amp meter. Continue removing fuses and disconnecting till you find the gremlin discharging battery. Use amp meter instead of volt meter for checking amps draw.

 

[CincyPlasmaTech]

I checked my Chilton's repair manual. The engine schematic shows that I don't have an alternator on my 1990 E-150 5.0L engine. All this time I thought I had one.

Vonbrown's and Bullfrog's replies make the most sense to me. Isolating the problem by pulling fuses makes for a lot less to look for when hunting down that parasitic draw.

I looked at a Ford charging circuit, and to my surprise, two failed diodes in series will connect battery positive to ground. I would disconnect the battery charging cable from the alternator to see if you still have a draw on the battery.

A bad battery with an internal short (between plates?) would have a noticeable discharge rate without anything connected to it. The battery voltage would drop over time.

I found my alternator!

 

[Weight]

You have an alternator on a 1990 ford engine.
When in a shop, I would rather change an alternator than replace diodes. If I replaced diodes and something else went wrong with the alternator, I would be liable. Exchange the alternator, K&H Auto Parts were good for a new one, if even needed.
We can all guess from here, but we are wrong. As I look out my window I can clearly see it is the drive belt. Sometimes you just have to trust the on-site mechanic.

 

[CincyPlasmaTech]

You have an alternator on a 1990 ford engine.
When in a shop, I would rather change an alternator than replace diodes. If I replaced diodes and something else went wrong with the alternator, I would be liable. Exchange the alternator, K&H Auto Parts were good for a new one, if even needed.
We can all guess from here, but we are wrong. As I look out my window I can clearly see it is the drive belt.   Sometimes you just have to trust the on-site mechanic.

I'm definitely an advocate for the mechanic. I have never been unfairly charged for services. I watch the mechanic forums so that I can be a good customer. My wife and daughter get completely different experiences. This mechanic seems disinterested in the work. So keep looking. The forum was offering suggestions for DIY electrical diagnostics, a good way to learn how difficult it is for the mechanic to do the work, or... how easy it is to spot a missing drive belt.

I don't swap diodes. I assume that the part is engineered to run for a certain number of hours, and then it is done. No small task to replace diodes or bearings or windings because the labor involved is worth more than the new part. When alternators get upwards $750, I expect a text message on the first diode failure,... from the alternator.

 

[highdesertranger]

FYI, a brand new AC Delco alternator for that vehicle is under 125 bucks from Rock Auto. so............ highdesertranger

 

[bullfrog]

I still carry a spare in some of my vehicles!

 

[Tessie]

Well, it definitely was the alternator. The local shop put the new one I bought for $136 and change in my vehicle for $125. Way better than $750 the dealership wanted. Problem solved! All that I have left to do is hook up the rest of my solar setup and move in and I am ready to hit the road. I am definitely stoked!

 

[highdesertranger]

good deal. highdesertranger

 

[bullfrog]

One thing everyone should be aware of is to have the new alternator checked by the store before having it installed. If it is installed and turns out to be bad and you furnished the part the mechanic will and should charge you for doing the job twice.

 

[Weight]

It is a rare shop that will risk installing parts you bring. I have given discounts on parts to help people in difficult times, but my shop discount at a parts store was not great. I hope the alternator didn't burn-out trying to charge the house bank.

 

[Tessie]

He went down the street to the parts store to get it, I just paid them, and then him after the install. The alternator isn't hooked up to the house bank at the moment. They are straight solar'
This is a great guy, and a darn good mechanic and I told him so too.

 

[Smitty716]

When I was working, if a customer brought there own parts I added to the labor rate and there was no warranty. To change that alternator should have only taken 45 minutes to an hour . So he charged her quite a lot . And if you go by book times like most shops do the customers get screwed because most the time with my air tools I cut that time in half .