Replaced alternator, still have same problems

[Jeremy T]

I just replaced my alternator today. The old one was putting out too low of a voltage at idle with and without a load on the engine. I took the old alternator to 2 auto parts stores. They both tested the alternator twice. So, 4 tests, and all 4 test failed that alternator. So, I replaced it. But I am still having the same problems. They even seem to be worse now. The lights dim alot after revving car up just a little bit and when idle settles, the lights dim alot. Also, everytime I put the car in park after driving the car almost stalls. Everything seems fine when I look at the scan data. Fule pressure is fine. Temperatures are now fine. The only thing thats irratic is the fuel trims dipping down quickly along with the car trying to stall when being put into park. It's like the car (pcm) is trying to catch itself and stabalize the idle. I first thought it was a iac issue but after trying 2 other iac's and a new iac the problem is still there. There's new plugs, wires, intake gaskets, new vacuum lines, clean throttle body. The fuel pressure is okay at 40 psi. It stays at 40-41 psi at all times. I've been dealing with this problem for a while now. I figured since I knew the alternator was bad that it would fix the problem since I replaced it because some of the sysmptoms seemed linked to the bad alternator, but I guess that wasn't the case. Please help! LOL.

[behlinla]

Jeremy, try charging your battery overnight and see if it makes a difference. Keep an eye on it while it's charging. A low or failed battery can cause these symptoms. If the battery doesn't hold a charge or gets really hot, then you should replace it.

[Jeremy T]

I should've mentioned that I had the battery tested twice and each time it passes with flying colors. I will do more test on the battery in the morning. I know when the old alternator was plugged in, the battery voltage was 12.2 volts, but as soon as I disconnected the the cables the voltage went up to 12.6 instantly. So, I attributed that to a bad diode or something inside the old alternator. As soon as the morning comes though, I wil check battery voltage. Any other things to check??? Oh, and there is no mil illuminted.

[behlinla]

The only other thing to check are your cables and connections. If you have a bad cable, ground (alternator bracket is clean, block ground is present), or connections the alternator will have to work harder. Bad connections make heat, so you can feel around once the car has been idling for a few minutes.

[sheila]

Fwiw, in-law's Windstar kept having batt. probs. requiring a jump. Myself, Advance Auto, Autozone and Walmart all load tested it and it passed with flying colors. End result was an internal short or something. New batt. 2 yrs. ago and it's been fine ever since.

[nbpt100]

Check your Bat voltage with the key off. All lights and power drains off. A fully charged battery is 12.65V. you will likely get 12.3 -12.6V. If it is lower something is dragging it down or your battery needs charging. The quetion is what and why? You may have a parasitic drain. there are lots of posts on this issue. Aftermarket stereos, alarms etc. are notorious for being the issue.

Here are some simple things I have learned to do with just a cheap DVM and some leads with spring clips or aligator clips. It may help you to find an issue or rule many out.

With the car idleing check the Bat voltage. Should be around 13.7-14.7 volts.

With the engine on, Turn on all of the accessories. Turn on high beams, blower on high ect. Voltage should be .5 volts over the Bat voltage. When I have done this on my Sable I get around 13.5 volts. The ECU can influence voltage but I don't know enough to tell you if that is an issue. Maybe someone knowledgeable can weigh in here.

To check the voltage drop on the neg side. Again, with the engine running, Turn on all accessories, EXCEPT the Rear Window Defroster. Have a helper hold the engine to around 2000 RPM and check voltage from Neg battery terminal to the alternator case. If it is More that .2 Volts you have a bad grounding connection. Check all grounding straps and ground connections.

To check the voltage drop between the alternator and the battery put your voltmeter between the POS battery terminal and the Positive lead on the alternator. With the engine at idle it should be less than .5 volts. If it is more check the wire for weakspots and all the connections in between.


Temperature does effect these tests. It should be done between 60-100 F.

If it is colder you will get higher voltage drops as the resistance of everything goes up as it gets colder.

Best of luck.

[SoNic67]

Probably the alternator was bad.
Now, you need to check the grounding and main connection to the new alternator...

[Scout1]

I think you still have a bad vacuum leak somewhere. Cap the line going to your vacuum distribution box on the drivers firewall and see if your engine will idle. I think your engine is idleing so slowly your altenator cant put out a good voltage.

[Blkfordtaurusman]

Did you you check and or replace that old Alternator cable? Also I would get out the Dremel or sanding bit and "make sure all factory ground locations are like mirrors" before you reattach the factory ground straps and cables.....(except your engine ground location under the battery) use steel wool instead. Your battery may have passed but are the cables in like NEW condition? Sometimes doing your BIG 3 is a good idea even if you don't have a car radio because you eliminate the problems of bad grounds and ageing (thin) alternator cables that eventually seem to plague our FORDS and the factory battery clamps are a bad joke with the rusting ground straps. It seems as if the electrical department assumed that we all would drive our cars in Arizona and only have our cars maintained by the Ford dealership every 3-4 months so we eventually would replace everything. My 3rd Bull was owned by a Highly educated man who always had the dealership maintenance that thing had blew me way. That poor thing had almost every thing replaced and sometimes more than once :-/

[sfhess]

Always have "new"/rebuilt/reman alternators tested before you leave the store.

It seems that the more difficult it is to remove/install one the more likely it is to be bad out of the box.

(Just pray you never have to replace one in a 95 Integra)