Hello guys- now I have two cars with charging issues (my XJS is eating batteries too!!)


On my X type :

No charging light coming on- cables are factory new. The alternator is NOT an original dealer part. I am going thru batteries every year. They are Diehards.

I am assuming the aftermarket alternator is having some type of intermittent malfunction here. I used to have a Mercury that did the same thing until the alternator was replaced with a factory unit. Only other thing is I am two miles from work and always take small trips. But sometimes I will get on the highway 10 miles +

Any thoughts?

 

Spike, part of your problem is the short trips. Starting batteries are meant to be maintained at 100% charge and by doing multiple small trips, it is cycling the battery too much and is actually hurting the cells of the battery. This would be one of the few cases that I would say upgrading to something like a marine battery may be in your best interest. They are going handle the constant start stop like you are doing. THe big thing that you need to keep in mind with that battery is you should run the battery till the car will not start and then put it on a charger to bring back to 100% atleast once a year, if not twice a year.

 

Sears Diehard batteries that I have used in the past are worthless IMO and never lived up to their hype..

Check your post voltage at idle..should be around 13.6V or more.

 

This is the second battery. Do you think short trips are my only problem? Or the alternator too

 

This is going to be the third battery though. The original new diehard , the replacement and now this one.

 

I hear ya,

I had a '92 Mercedes 300E from new, the original battery lasted 4 years..the next three batteries one year apart where Diehards..just saying.

Check the battery post voltage like I suggested next chance you get..If you don't have a meter..AutoZone will check it for you for free.

 

Well I could not test it at the post this morning because I had a meeting at work, but I did get a brand new battery and I did place the message centre in engineering mode. Driving with the lights on, AC on it keeps on dropping below the 12.6 magic number consistently. Occasionally it would go above 14 but either my alternator is misbehaving or some other ancillary like the fans or the lights are shorted out and drawing way too much power. How the hell to find out? IDK.

Here is a video of me driving in engineering mode wth the new battery right out of Sears::

 

That looks like bad battery cables to me...I know you said they were new..but did you replace all the ground (neg) cables as well as ALL the Red positive cables...?

 

yes, all cables. The only one that is not factory is the possitive link that runs to the fuse box. The main possitive, the negative, the negative link are all new Jaguar parts

 

I'm at a loss then..the only thing left to do is measure the voltage right at the terminal on the alternator. If that is low like you read on the DIC in engineering mode, then it must be in fact the alternator...But if it high like 13.6v to over 14v then you have a bad cable from the alternator to the starter to the battery..(the real long one).

 

SPike, I want you to try something for me. First, connect a multimeter between the lead part of the battery post (not the terminal, but the part attached to the battery) with one lead and then place the other against any metal part of the engine. What is the voltage that you are seeing here? It should be under 0.5 VDC. If you are getting over 0.5 VDC, you have a high resistance connection somewhere. Just to ask a silly question, when you installed the new battery cables, did you take a wire brush and clean up the surfaces to make sure you had good connection? Even a small amount of rust in this area can cause some interesting situations to occur.

Next, connect the multimeter between the lead of the battery posts (again, stay clear of the terminals attached to the wires). Are you getting around 13.0-13.6 VDC? If yes, then your alternator is outputting what it should. If it is up around 14.0 VDC or even possibly higher, then you have a bad wire somewhere between the battery and the ECU (making the ECU think the car's voltage is too low). If it is down around 12.5 VDC, then your alternator is not outputting what it should or else you have a bad cable between the alternator and the starter. Unfortunately, measuring the voltage directly on the alternator is a bit of a pain. BUt, if you can, measure from the starter to the alternator to see if you are under 0.5 VDC drop on that wire. If yes, then the wire is probably good. If no, then you have a bad cable.

The next check I would do is to measure between the major post on the fuse box in the engine bay and the chassis. If you are getting something up in the 13.0 VDC range or higher, then we know between the engine bay fuse box and the battery is good. If not, the cable between the fuse box and battery is toast.

Now get into the interior of your car and pick any fuse that is powered directly off of the battery. PUt the red probe on to one of the posts in the top of a fuse and the other to the chassis. Are you getting roughly the same voltage here that you did when you measured the terminal on the engine bay fuse box (within say 0.2 VDC). If yes, then this is pointing to a problem with the ECU and it is not seeing the battery voltage correctly. If no, then you are looking at a bad wire between the engine bay fuse box and the passenger area fuse box.

 

In a all your wonderful testing procedures, you never mentioned which battery post he should be testing from..+ or -....or if the car should be running

Just to be sure everyone understands...a 14+V level is not a bad thing or an indication of a problem,,

If the car is first started the Alternator's output will be 14+volts for a few minutes and then it will dwell back to 13.6v or so in about 10 minutes..This is a designed charging program of the X-type..So to say 14volts is not a good thing and an indication of a problem, would be misleading and confusing,,,

 

Thanks so much guys, but I am confused!!

I can test for resistance on the cables by putting one end of my multimeter in the BATTERY POST and the other in a metal part? How does this test resistance in the cables? What post? Do I disconnect the other? I am sorry I am not very electrically inclined

 

Let's just do ONE thing at a time....Seriously, I want to help you solve this issue.

First; While idling...Take one of your meter leads and touch or connect it to the alternator + output terminal..(this has a large red cable connected to it, move the red rubber cap over off the terminal screw head if there is one)..and then touch the OTHER lead to the center of the POS (+) of the battery post..not the red cable connector to it.

you should read almost nothing, maybe a 10th to 100th of a volt DC + or - is all..up to half a volt could be normal..

Report back then well move to the next test.

 

Spike, doing a resistance check of a battery cable is like trying to fill a glass with a fire hose. What I mean by this is that a battery cable is meant to handle very large currents. If you think of voltage in a different way, as in a resistance times a current (this is known as ohms law), if your battery cable has any resistance to it, it is going to be dropping voltage, lots of it. If we make an assumption that your battery cable has a 0.1 ohm resistance (the minimum resistance that most multimeters can read down to on their most sensitive scale) and your car is pulling 50 amps (minimum loading of simply the engine running, and say the A/C system), this would then mean that your battery cables would be dropping 5 volts (0.1 ohms x 50 amps = 5.0 volts). So, as you can see by this example, even a very small resistance with a higher current would be something that would be easily missed by a resistance reading yet result in a very significant voltage drop. So, unless you have access to a resistance bridge (ie, a very sensitive resistance measurement device), measuring the resistance of a battery cable is not going to tell you much. If you can see a resistance, then the cable is well beyond shot.

Another general rule that gets used in the electrical world is not having more than a 1.0 volt drop between a source and the load. This is the standard used in most automotive applications. So, with a battery cable, assuming that the alternator is outputting its maximum output (160 amps), that would mean that the battery cable cannot have more than 0.0066 ohms of resistance. This is well beyond what any standard multimeter can read.

 

I don't want to overwhelm you with electrical engineering and calculations, just trying to keep it simple..

So you can only listen to one person and be dazzled by all the science behind a couple of wires and their electrical resistance properties and conductivity of copper and if you think it will be of bigger help..I then will yield to the master Thermo..and bow out of this discussion.

Good luck

 

Thank you both for your replies. Both replies are greatly appreciated.

As far as measuring resistance-if I did this right- there is non- which makes sense since I mentioned ALL the cables are factory new. I can't imagine they've gone bad in a few months.

I think I kind of found my problem-it's the alternator-I think.

I decided to get on the freeway for 30 minutes and drive at normal speeds-the engineering mode display showed it started at 14.5 then 12.8/13 all the way. With the AC on high. After doing that, I got on the street and it remained 12.8 /13 thru stops and idling. After that I stopped for some coffee and headed home (no freeway) and again it started at 14.5 but quickly dropped to 12.6. I then turned all the lights on and it stayed at 12.6 while driving, but it definately went below 12.6 at a few red lights.

My conclusion is that this aftermarket alternator can't keep up with my little short trips. It needs to get on high RPM's to do its thing properly. I don't know if driving on the highway once a week will keep my batteries from dying, but there it is. I think the fact that the voltage is consistent at high consistent high RPM's -in incredibly hot weather if that matters- if proof the cables are not an issue-

 

Hi, Sorry to but in on your thread but it seems interesting.
You will see from the extraction from the workshop manual that the alternator is preset to deliver 2 voltages. 15.3v at start for a prescribed time and then 13.6v thereafter.
I have always worked on the assumption that after approx 5 minutes the alternator should be charging at between 13.9 and 14.2v at idle without any load. When a load is added the voltage should not drop more than 0.5v as the alternator reads the load and compensates for the draw. When the load is removed the voltage should return.
If the voltage drops more than 0.5v and continues to drop then the alternator would be deemed to be faulty.
If the battery is fully charged (which it is not when new) then the voltage would be no lower than the set 13.6v. So the voltage being shown in your video tells me your alternator is not within range.

Battery and Charging System - General Information - Charging System
Description and Operation
Vehicles with 2.0L, 2.5L or 3.0L engines
The charging system consists of a 120 amp output generator and regulator assembly which generates current to supply the vehicle electrical
system with electricity when the engine is running and maintain the battery in a charged condition.
The generator is belt driven by the accessory drive belt.
For additional information, refer to: Accessory Drive (303-05 Accessory Drive, Description and Operation).
When the engine is started, the generator begins to generate alternating current (AC) which is converted to direct current (DC) internally.
The DC current and voltage is controlled by the voltage regulator, (located inside the generator), and then supplied to the battery through
the main battery positive cable.
The generator is solidly mounted to the engine timing cover and is driven at 2.8 times the engine speed.
Vehicles fitted with manual transmission have a one way clutch fitted to the drive pulley, which prevents torsional vibrations from the
engine being transmitted to the generator.
The engine control module (ECM) can switch the voltage regulator between two voltages to optimize the charging of the battery.
The low voltage regulator setting is 13.6 volts and the high voltage regulator setting is 15.3 volts, measured with the generator at 25°C
(77°F) and charging at a rate of 5 amps. These values decrease with a rise in temperature or current flow.
The ECM determines the voltage setting of the voltage regulator. The high voltage setting is always selected by the ECM once the vehicle
has started. The ECM determines the period of time that the high voltage setting is selected for.
There are three different time periods selected by the ECM which is dependent upon the vehicle conditions when the vehicle is started:
The longest time period is selected if the ECM determines that the vehicle has been 'soaking' for sufficient time to allow the engine
coolant temperature (ECT) and the intake air temperature (IAT) to fall within 3°C (37°F) of each other.
The intermediate time period is selected when the ECT and the IAT is below 5°C (41°F).
The shortest time period is the default time and is used to provide a short period of boost charge.
At the end of these time periods the voltage is always set to the low voltage setting to prevent the battery from being overcharged.
The time periods are variable depending upon the temperature and the battery voltage. The target voltage of the battery varies between 14
volts and 15 volts depending upon the ambient temperature and the vehicle operating conditions. Once this target voltage has been
achieved, providing the vehicle has been operating for at least the shortest time period, the ECM will reduce the voltage regulator to the
minimum setting of 13.6 volts.
There are three wires connected to the generator from the ECM by connector EN16:
EN49-1; RG wire, is the voltage regulator request setting from the ECM to the generator.
EN49-3; OG wire, is a pulse width modulated signal (PWM) from the generator to the ECM which enables the ECM to monitor the
generator load on the engine.
EN49-4; U wire, is the charge warning lamp signal wire from the generator to the ECM.
If the voltage request signal wire (EN 49-1) is open circuit or short to battery positive, the generator will charge the battery at a setting of
15.3 volts. If the wire is short circuit to ground, the generator will charge the battery at a setting of 13.6 volts.
A fault in the wiring or the connections from the generator to the ECM, will cause a fault code to be generated and stored in the ECM and
the charge warning indicator lamp to be displayed in the instrument cluster (IC) after a short time.
The charge warning indicator lamp is operated by the IC after receiving a signal from the ECM through the control area network (CAN).
With the ignition switch in the RUN position the charge warning indicator lamp will be displayed in the IC when the generator is not
generating power.
If a fault is detected with the generator a fault code will be generated and stored by the ECM. The charge warning indicator lamp will also
be displayed in the IC.
Units should be repaired as an assembly and not dismantled for repair.
For additional information, refer to: Generator - 2.0L NA V6 - AJV6/2.5L NA V6 - AJV6/3.0L NA V6 - AJ27 (414-02 Generator and Regulator,
Removal and Installation).
Vehicles with 2.0L and 2.2L diesel engine
The diesel charging system differs from that used in petrol-engined variants in that it incorporates a 'smartcharge' function.
This function is capable of supplying infinitely variable voltages to the battery, depending on the temperature and on the current
requirements of the battery.
The system continuously monitors the battery voltage and temperature (via the ambient air temperature sensor), and uses a map of both to
deliver the optimum charge to the battery.
Another feature of this system is that it uses a 'wake-up' and 'sleep' strategy, initiated by the ignition switch position and ECM, rather than
being constantly active, to avoid current drain.

Roger

 

@Rchiv

Thanks.

So, I thought the magic number was 12.6 while driving? And I thought 14.something was the start up voltage.

I would really be interested in knowing what someone's car whose charging system is in good condition is doing while driving with/without load and at idle.

 

12.6v is not enough to be charging the battery. It should nit be below 13.6v at any time and is governed by the ECM via the draw and temperature.
My 2.2D idles at 14v with out load and 13.9 with load at 1500rpm.

Roger