Failing Alternator can effect starter? (1 Viewer)

[fjdemon]

So, here is the situation. I believe I have it resolved, just curious to get a confirmation on what I think. Basically the car wouldn't start when I turned the key. I got a little bit of ticking and the lights would dim. My first guess was bad connection or battery, I checked them and everything was good. I just trickle charged the battery and the starter was just rebuilt about a month ago. A minute later she fires up like normal. So I drive down the road and I stop to get gas, turn off the car, immediately turn it over and fires up. I go inside to pay come out, and get nothing on the key turn. Eventually it starts, so I go to auto parts store to have the battery checked and they tell me everything is fine, but the alternator diode is failing. I swap the alternator in the parking lot and have not had an issue since. I'm looking for an explanation as to how this works. I assume that the alternator may have been failing and was drawing to many amps keeping the starter from turning over or am I way off? Is that possible? I just want to make sure the starting issue is resolved. Thanks in advance.

 

[Wile E Coyote]

I'm not seeing how the alt should cause it to not turn over. If the battery is indeed fine, then I think you need to check out that 1 month old starter (and it's solenoid of course) and the battery-to-starter cable...closely. Disconnect both ends of that cable and do continuity and resistance tests, and look over every inch of the cable.
The heat of driving increases electrical resistance and will exacerbate any already weak spots.

 

[hj 60]

If the diode bridge fails current can leak back the opposite way and drain the battery in a day or more.
So maybe your battery was fine but even when its empty it will tell you it is 12V, you need to measure the kick behind it in amps.
More amps=quicker starter, less amps=no starter (click, click sound)

The person who got it first is more familiar to you guys than I knew

Benjamin Franklin understood the pos and neg way better than me:
http://en.wikipedia.org/wiki/Diode_bridge

 

[fjdemon]

Yeah it's super strange. I have had old trucks in the past where the starters get hot and go into slow motion when you try to start them after they are at running temp. Typically if you wait they cool off an work again, but this starts right up after you stop. I also thought it might be in the safety switch on the clutch. I checked it and it was already disconnected.... I'm going to have to trouble shoot this. I'll check the pos line going to it. When it starts it starts hard, super powerful as if there was no issues. It could simply be in the ignition switch, but it seriously hasn't failed since I changed the alternator.

 

[TS888]

As HJ 60 said, if the alternator diodes are failing, the alternator will draw on the battery, and not charge it well. Depending on the quality of the battery test tool, it might read that the battery is good when it is in fact weak, holding just a surface charge.

 

[oleblue62]

I have an 89 Volvo 240 that had something similar happen. I took it to my amazing Volvo only mechanic, first thing he did was test the battery (even though it started no problem for him yet wouldn't for me under the same condition). Battery tested fine. Later, he decided to put it on a longer battery test, and sure enough it was a bad battery. I had just replaced the alternator 2 months before. Starts great again.

I bet its the battery, and hope its the battery.

 

[Elbert]

I don't see a connection between bad Alt and no start on FJ60, obviously if you are trying to start with a fresh charged battery. The only way to really check a battery is to have it load tested.

 

[fjdemon]

No, idea. I will take everything you all said into account and see what happens in the future. So far no starting issues. Very weird... wires all look good. I'll let you know if anything else happens, if not all is ok. thanks