AC Killing Alternator when on High

[cobra3073]

Hi Folks,

I have a 2003 Marauder that I have had at the "Dealer" several times for electrical type issues.

Initially (about 2 years ago), I had an issue whereby the radio would start receiving "static." Took it in and initially they replaced the battery. Still had the problem so took it back in and they replaced the alternator. Unfortunately, they installed the alternator for a Mercury Grand Marquis. When I took it back they replaced it with the "correct" one.

Approximately two months ago, I noticed that the battery light came on briefly. I took it to the dealer whereby they advised the alternator was "bad' and replaced it under warranty.

Three weeks ago, I noticed the battery light came on again while I was running the AC on high. When I turned it down, the battery light went off but I immediately took it back to the dealer. It has been there every since. They advised they have again replaced the alternator but are still seeing a discharge when they run the AC on high. They are now suggesting that I spring to replace the AC compressor but are upfront in stating that they are not sure that is the problem.

They claimed they have contacted "Corporate" for advice and have done everything recommended, so far. Has anyone else had this problem or have any suggestions as to what I might have them check?

Thanks!

BT

[RF Overlord]

Nothing about the compressor can cause electrical issues, except:

The clutch field coil drawing too much current

or

The compressor is pulling down the RPMs and the PCM is not compensating as it should.

If the clutch coil is bad, that can be replaced separately.

[Zack]

All my Marauders go to 12v with AC, headlights and fan on high

[B.C. Bake]

Nothing about the compressor can cause electrical issues, except:

The clutch field coil drawing too much current

or

The compressor is pulling down the RPMs and the PCM is not compensating as it should.

If the clutch coil is bad, that can be replaced separately.

Good point on field current, but if it is drawing too much current or out of tolerance it should take out the ac fuse. I would look more at rpm.
Or the right size battery, can it handle the load? :)

[B.C. Bake]

Now, I almost forgot in my last post. Your problem started with static on the radio.

I'm not sure if I would of replaced the battery, there is allot of OEM radios here that started going bad with static as a sim-tom.:rolleyes:,,,

[Zack]

Using cheap cell phone chargers causes static in my radio, to the point you can't hear anything

[cobra3073]

For clarification, the car actually wouldn't start after the radio static issue. And again, this was about a year or so ago. After replacing the battery and changing the alternator, that particular problem "went away."

According to the Service Advisor, "Corporate" had advised them to replace one of the ground wires (?). That was done and the problem seemed to be lessen but the alternator was still dropping when the AC is placed on high.

I apologize for not having more detailed information as to what "they" have done to try and resolve the issue. I plan to go by tomorrow and speak with the mechanics (couple of them) who have been trying to chase down the problem. Perhaps I will then be able to ask more intelligent questions of you guys.

BT

[RF Overlord]

the alternator was still dropping when the AC is placed on high.So this issue only happens when the HVAC blower is on high?

The BMSC has a bypass relay for the high-speed function...it's a hard connection versus the PWM circuit that feeds the blower on lower speeds. Maybe your blower motor is faulty?

[cobra3073]

So this issue only happens when the HVAC blower is on high?

The BMSC has a bypass relay for the high-speed function...it's a hard connection versus the PWM circuit that feeds the blower on lower speeds. Maybe your blower motor is faulty?
That could be it.

Is there any test that would rule this in or out beyond replacing the blower motor?

Thanks!

BT

[lji372]

All my Marauders go to 12v with AC, headlights and fan on high

Now you tell us.

I just took an alternator back to the rebuild shop and they went through it and said everything checks out grrr. Had a squeaky bearing that needed tending to anyway.

I mean someone did the work, I do not admit to getting dirty ;)

[Turbov6Bryan]

Buy one of these. Not this one, I'll take too long to get here

Stick it in your lighter hole

Now let us know what your volts are while driving vs stopped

https://www.ebay.com/itm/122082864342

[8UWITH6]

My eaton swapped car with overkill upgraded wiring, etc but stock alternator with the AC on, HID fogs and parking lamps and stereo on full tilt boogie reads 12.0 to 12.2 sitting at a light with the brakes on. Once you come off of idle and accelerate away I am mid 13s. Zero given.

Try adding some grounds or cleaning the existing ones. Eliminate any accessories added to the electrical system if possible to track down the issue.

[cobra3073]

Ok, I got with the Service Manager and the Service Advisor this morning.

They noted they were looking at the clutch field coil (as recommended by RF Overload) as a possibility.

However, after much conversation we decided to ask you guys for some additional advice. So, here it goes:

Zack - when you say your Marauders all drop to 12V when running your accessories, do you also have intermittent situations whereby the battery light comes on?

B.C. Blake What size battery are you (and others) running in your Marauders?

As I inferred in an earlier post, they did change the battery and I was advised this morning that the battery they used is under warranty so they can get a bigger one, if necessary.

It was noted that the problem was lessen with the addition of the ground wire and they did not see any incidents of the battery light coming on or the RPM dropping while testing the car on yesterday. We thought about my just taking it and driving it for a couple of days to see if the problem "comes back" but decided to wait on y'all responses to the above questions first.

Again, need to know if others are experiencing the battery light coming on intermittently when HVAC is on high when the alternator drops to 12V and as to what size battery y'all are running in your Marauders?

Thanks guys!

BT

[Zack]

It is my experience that cars with no tune to raise the idle have a greater chance of the battery light coming on
The rpm setpoint in drive is 544rpms.
Thats really low.
I never let any car go below 700

[TORINO]

If it was the a/c clutch it would do it on low fan also. If it was the blower motor it would do it with just the fan on high with or with out a/c on. Battery size should not be a factor while engine is running should not be pulling on the battery after start up. You add ground wire ? Should add a ground from engine to frame and engine body to rule a ground problem out.

[cobra3073]

You add ground wire ? Should add a ground from engine to frame and engine body to rule a ground problem out.
Yes, they added a ground wire.

Are you saying above that there should be two (2) ground wires added? One from the engine to the "frame" and one from the engine to the "body?"

Thanks!

BT

[fastblackmerc]

I'd replace all the grounds - battery to engine, battery to body & engine to body.

[cobra3073]

OK, here is what I have directed them to try:

1. Ensure engine RPM is set at 700 in drive

2. Change all three grounding straps

We will try these changes and see if the problem persist. If it does, will then look at the PCM.

Please let me know if there is anything that I might be missing and I will keep the board informed as to my progress.

Thanks Guys!

BT

[Zack]

Raising the idle is only accomplished through pcm reprogramming

[ChiTownMaraud3r]

My eaton swapped car with overkill upgraded wiring, etc but stock alternator with the AC on, HID fogs and parking lamps and stereo on full tilt boogie reads 12.0 to 12.2 sitting at a light with the brakes on. Once you come off of idle and accelerate away I am mid 13s. Zero given.

Same. Thought my car was still broken. :beer:

[TORINO]

Besides good grounds they need to be sure you don't have high resitance / bad connection between the positive lead at the alternator and the positive cable at battery. With a load tester on the battery making the alternator put out a good amount of amps you should only be losing a few volts ( like 2 )between alt and cable at bat. When I say two volts that is the resitance in the connection between alt and bat. You put a volt meter between the two connections

[SergntMac]

All my Marauders go to 12v with AC, headlights and fan on high

Yup.

03 300A...Ditto
1x blower car...Ditto
03 SB/no tune and with tune...Ditto
03 SB/with tune, new battery and correct alternator...Ditto

Circumstances...All on...A/C on max air, headlights, radio w/CD changer, brakes, turn signal, fog lights, in gear, whatever.

All my cars have a ScanGuage, so I can watch it happen. Drops from 13.6v to 12.2v a tenth at a time, and the light starts a warm glow. At 12.0v it's bright red on. Either I shift to neutral, or just tickle the throttle, it all goes away.

BTW...It shows about 14.0v when first starting up, but that settles down once the idle drops. Doesn't mean anything here, I just like to hear myself type. More BTW...it's the same program on both of my Shelbys (err...sorry Zack) blower car and N/A.

The only affect I am not sure of is humidity. On hot sticky days, the idle will drop to 590rpms or so, ready to die out. Usually, on dry days, it will hold 690-710rpms and all is well. The only times--just twice--the battery was over 4 years old, and only once, the altenator died.

The problem with "contacting Corporate" is that they don't know how to shrug or say "don't really know". Any response is usually a guess. Anyone coming to Cleveland can ask me about "a clunk on a right turn". It hilarious.

Personally...if this was my problem (and it has been) I wouldn't concern myself until the light stays on after you correct engine speed, or, kill a battery.

Y'all be safe.

[cobra3073]

THANKS Guys!!

I am going to pick it up tomorrow morning. I was assured they have set the idle.

Quite frankly, I was pleasantly surprised when the mechanics, service manager and service advisors admitted when they did not know and welcomed the inputs from the folks here on the Site.

You guys ROCK and I am going to spend more time on here rather than spending all my time on the '69 Mustangs and FE Forums. I have six vehicles, all Lincoln, Mercury, Ford products:

1. 2 '73 Mustangs (one a Grande with a 472 {.060 460}, the other a Mach 1 is going to have a full on 545 that has been dyno'ed at 707 HP/736 Torque)

2. An original "H" coded 1969 Mach 1 that I have changed to a 428SCJ clone/tribute

3. A 1989 5.0 LX (Stock)

4. A 2015 Lincoln MKT (Stock)

5. ...and then there is my daily driver the 2003 Marauder

Quite frankly, all of my experience has been with the non-computer cars. I am one of the original Moderators on the 1971 - 1973 Mustang forum.

Anyway, again I THANK you guys and I am going to try to REALLY get into the site here, now.

BT

[Turbov6Bryan]

When you get advise from people from this site please use it. :)

If you don't get what you want from taking your car to the stealership, post back up and let us know. Certainly we have a solution

[B.C. Bake]

When you get advise from people from this site please use it. :)

If you don't get what you want from taking your car to the stealership, post back up and let us know. Certainly we have a solution

+1 ;) oh and on the battery I'm using an Optima red top ...But I would not advise that today,,,I think they changed manufacture Quality. Sorry for the slow reply I had to leave for a couple days.

[Zack]

Im sure a lot of alternator draw can be remedied with external headlight relays.

[RF Overlord]

Zack, the headlight relays are primarily to reduce the voltage drop caused by the switch, the LCM, and (mostly) the undersized wiring. The total power consumed by the headlights remains the same, so alternator draw would be unchanged.

[ctrlraven]

One thing I noticed that wasn't asked was, do you have under drive pulleys installed on the car?

[cobra3073]

One thing I noticed that wasn't asked was, do you have under drive pulleys installed on the car?
No, I don't have under drive pulleys installed. The car is completely stock, to the best of my knowledge.

Since picking it up on yesterday, I have not had the problem.

BT

[ctrlraven]

No, I don't have under drive pulleys installed. The car is completely stock, to the best of my knowledge.

Since picking it up on yesterday, I have not had the problem.

BT
I figured as much but never hurts to ask since they can lessen the charging output and stock idle rpm in drive is already low to begin with.

Hopefully the problem is fixed!