I have a very odd issue when my car first starts I don't get good output from the alternator until my car comes up to temperature. My electric fuel pump runs slow, the lights start to dim and finally when my car gets to normal operating temp, all of a sudden the alternator kicks in and I'm all good. This happens 100% of the time exactly the same way.

I have good ground on the battery cable. I have the alternator wire hooked up to the battery through a second gen fuse block with a 60A fuse. It may have something to do with the "exhaust overheat" light because when the alternator does kick in that light always flashes. Although it could just be because of a power surge as well.

Any ideas?

 

Does it work correctly if you hook the alternator up directly to the battery (as it was before you added the fuse block)?

 

Have the alt tested to determine if it's the alt that's at fault, or some other part of the wiring.

Most likely cause is the alt has a crack in a stator winding, a cracked or cold solder joint, or a physical failure in a rectifier. As the alt heats up with the engine, the materials will expand slightly as most metals do, and close the open circuit.

Could be other issues, like the alt's grounding to the engine (thru the water-pump housing via it's physical bolt-down) is weak/dirty/etc, and improves when thermal expansion tightens things up. Connecting a heavy-gauge wire from the alt body to a clean engine ground would make this improve, if it's the actual problem.

 

I have several alternators lying around and it does the same thing with every one. It also continues to do it when starting a warmed up engine until I rev it above 4000 RPMs.

I guess I haven't tried to hook the alternator directly to the battery.

 

i would suspect something with the car then. i think i would start with the big power wire, make sure its got a good connection on both ends.

the second thing i'd look at is one of the other wires that go into the back of the alternator, i forget which one it is, but there is one that just feeds the alternator voltage back to the regulator, maybe this one isn't solid.

 

Where is the regulator located? I thought these alternators were internally regulated.

 

the regulator is in the alternator, but it gets the voltage signal from the car somewhere.

 

i looked at the diagram, and the black with white comes from the ignition switch, and i believe it tells the regulator what its charging at, the other wire, white with black goes to the choke and check relay, and then the voltmeter in the dash.

the choke and check relay is a bit weird, you might wanna check that as well

 

Start by taking your DVM and measuring the output voltage of the alt when this is happening.
That will tell you if its the alt or some other thing in the wiring somewhere hopefully. Might want
to measure at the battery as well.

 

DiniDriver's argument is probably still pertinent. Only you have the same symptoms with different alternators, then it's in the wiring between the alternator and the main fuse at the fuse box. Things getting better with heat, expanding metal is the only explaination.

 

OP, do you rev the car up above 3-4k before it warms up? Is this a new issue or has it always been that way?

If you haven't done so, immediately rev the car up when starting and see if it does the same thing. Alternators have a sensor in them that switches them "off" while the car is off, which stops them from draining your battery (remember- an alternator is just an electric motor).

If this is a new issue, I'd say it's likely that the brushes inside the alternator are worn, and expanding when it gets warm enough, to finally make contact (like Divin said).

 

I've made a few changes such as changing to another alternator I' don't think I've ever tried and ran a new wire b/t alt and fuse block. I haven't tried it yet as I'm also doing some other minor improvements that I haven't quite finished up yet. I'll post back results when completed.

 

When i switched to the c130 alt out of a buick i did the wiring to where the alt is always on. And when it sat for 2 months my battery didnt drop at all, so maybe looking into wiring it like the upgraded mod might help you.

 

Well got things put back together last night and I had full voltage right away. I believe the old alternator was to blame. I think last time I thought I switched it out I put the same one back in (was doing a bunch of other stuff and had parts every where).

So there must have been something going on like was mentioned where the alternator would work after it heated up.

Good FYI if anyone else has the same experiance.