Car is slow to crank over when starting

I have a 2007 Dodge Charger. Battery light came on, I had AAA come out to me to test everything because I didn’t want to be stranded just in case the car died while I was out doing errands.

So I waited for the guy, and when he hooked up his gadget, I forget the name, but he connects it to the battery. It tested the alternator, battery and the starter. Turns out, the alternator had an open diode. Battery was in good shape and the starter too.

I ordered a battery, and had to wait to get it installed because my mechanic was busy working on a whole bunch of other cars. So I had to use the whining alternator for a whole week before I could get the new one in.

But he got it installed. And put everything back together where it should be (I think). He told me to start the car. It started up beautifully! No troubles at all.

A couple days later, it started to struggle cranking to start. Taking into account the battery and starter are good and the alternator is like-new (refurbished). I do not understand why it’s having issues.

There’s no battery light on. Why would it, a couple days later, start having an issue? Could my mechanic have not fully connected wires to the alternator? When loosening the idle arm to loosen the belt, could the have messed with the timing?

So frustrated, sorry. I’m not mechanically smart. But slowly learning.

You said "So I had to use the whining alternator for a whole week before I could get the new one in. "

If you were able to drive for a week with the old alternator without having your battery go dead, there was nothing wrong with the old alternator. (But what is this about it whining?)

Anyway, now you have a new battery and a rebuilt alternator? First thing I would do is check all the battery cable and ground connections to make sure they’re clean and secure. A bad connection can impede the flow of electricity to the starter when you crank the engine.

The alternator was “whining” (the sound I thought it made. Push down on the accelerator, it got louder) longer than a week. It was the timeframe from picking up the new alternator and when my mechanic could fit me into his schedule. But ever since the new one was put in, doesn’t make a peep of a sound anymore. Battery isn’t new, just in good shape. But I did think about the posts/clamps being dirty from being taken off the battery for an extended period of time and dust being everywhere at the shop. Or the parasitic drainage of the battery with a lot of aftermarket sound equipment in the back seat and trunk.

Yes, your compulsion to p*ss off all your neighbors and wake up all their babies probably is the reason you’re having charging system problems. It’s karma.

Eventually your car’s fastening systems will begin to fail too, and your panels will all be shaking and rattling. Again, it’s’ just karma.

Im confused??? The sound equipment is turned way low before I get to the house and after I leave the house. Never right when I get in the car. I have respect for the neighbors and their sleep.

Your high power aftermarket system is placing too much demand on your charging system.

Oh, I have a capacitor that helps take the strain off the the alternator and battery. Along with a circuit breaker installed to prevent blowing fuses. But I do understand now, thank you for explaining. And I agree. I wouldn’t have gotten the system if I didn’t think my alternator wasn’t big enough to handle it. FYI, it’s a stock 160amp, but recently replaced with a refurbished 160 because of the diode issue in the old one.

Do they make a higher output alternator for your car? Caps are for filtering not increasing power.

Bat is probably bad . Faulty alternator may have done it in. Check bat v during crank no lower than 10.5v

@knfenimore‌ Unfortunately, they only have the 140 and the 160. I would have been a little skeptical to get anything bigger than what the car came with since everything is controlled by computers to regulate. The capacitor was installed to help control, take the strain off how much the sound system drew off the battery along with eliminating flickering headlights whenever the bass hit.

@cj2‌ would that be on a cold or warm start. Sometimes it doesn’t have an issue starting up like normal, depending on how long (varies) the car is left to sit.

Capacitors are electronic energy storage devices.

Ever hear of a capacitor start electric motor?


Hmm. I don’t think I have

Those huge capacitors are nothing but a joke…The can store electricity ( very little ) but where does it get it from, the alt and the bat…they do nothing and basically in parallel with the cars electrical system. I laugh when I see all those things hooked up on car stereos.

Down here in Florida, if a law enforcement officer can hear your stereo 50 ft away from your car its a 116.00 ticket ! I wish someone would invent a remote control, so when you are next to someone blasting their music, you can hit a button and smoke it.

“would that be on a cold or warm start. Sometimes it doesn’t have an issue starting up like normal, depending on how long (varies) the car is left to sit.”

Just a general test i do to determine condition my bat is at under load. Probably a good test for worst case cold conditions. The high cranking load will pass quickly so to get a better look at the voltage maybe floor accelerator to keep it in cranking mode longer.

It’s important to note whether the crank is weak thus taking longer to fire engine or if the crank is strong and just taking the engine longer to fire due to other issues.

FYI, diodes can fail in more than one way. A single diode failing open will usually allow the alternator to continue to work, but it will put more load on the other diodes, which might cause them to fail eventually too. A diode can fail with a short too, and that condition can put a drain on the battery as you let the car sit overnight. So the next morning the battery might not have enough juice to be able to crank the car.

As mentioned by others in this thread first order of business with a slow crank is to make sure the charging system is working correctly. Any shop can do that, some will do it for free. Next is to make sure the battery connections are clean and tight. Still have a slow crank? Have the battery load tested. Still a slow crank? And the battery is fully charged? Ask the tech to measure the voltage at both starter terminals (measure between the starter terminal and the starter case) during attempted cranking. If either is below 10.5 volts, find out why. If both are 10.5 volts or above and you still have a slow crank, that usually indicates either the starter solenoid contacts are bad, or the commutator contacts or brushes are bad, and means replacing or rebuilding the starter.

@cj2‌ Ok. Really appreciate that. I wish I had all the equipment to do it myself, but other priorities come first. I’ll see what my mechanic says.

@GeorgeSanJose‌ That’s a lot of information. Thank you. The old alternator started the car fine. No slow crank or anything. The only wrong thing with it was noise it made when the car started (because of the open diode), but going away after driving awhile. But I got the new one in, and that’s when the cranking issue started. I’ll have to go to the shop tomorrow and see if my guy can do the tests. Definitely need to know the issue. Hopefully easy fix. Don’t have enough for a $200+ battery at the moment. And I’ll clean the the posts/clamps while I’m there too.

Your vehicle, without the sound system, has it’s normal electrical demands (lights, fan, electronics, etc). Your alternator was designed to cover that load with some added capacity safety margin.

Now add in your 160 amp sound system. Ouch!
Your alternator is likely only capable of producing 100 amps or so.

As you drive down the highway listening to your music, you’re draining your battery - because the alternator can’t keep up.

Also note that alternators aren’t designed to continuously operate at full current output. The heat they generate at full output greatly shortens their life.

my son had to use two heavy duty, very expensive batteries to keep up with his sound system in an old corolla he used to have. I still have a garage full of amps…

News update… Battery is in great shape. No bad cells, alternator charged it back to 100%. It’s a tank. Only concern now is that it’s producing more cranking amp on a startup. Supposed to be 730cca. When I tested it, it came out to 836cca. Good or bad?

@JoeMario‌ I understand. And I wish I could reprogram the brains to run off something bigger. But these new cars make a lot of things more complicated and more dependent on shops when trying to put in bigger things. Like a V6 upgrading to a V8. The stock ECU (I think that’s what it’s called) isn’t designed to operate it properly.

@wesw‌ I have a small battery connected straight to the sound system. Saves on juice for the car battery.

Have you solved the slow cranking problem?