Hil everyone, hope you are all doing well and having a great summer!
I recently was hospitalized for 6 weeks and my battery died. It probably needed to be replaced so I had it towed to a local service establishment and they put in an Interstate MTP-49 battery. This seemed to work well but a week or so after I began having an issue with the car stalling at a stop after starting it and driving a short distance and the battery light came on. It started right up again. A few weeks later as I was starting the car it did not start right up. I tried again and it did start but then as I was driving and then stopped at a light a short distance away it stalled again and the battery light came on. I have had this car 10 years and it has never stalled. So, I inquired about what battery was installed. I wanted to be sure it is the correct battery. Could it be the alternator? Any ideas on what to check first before replacing an alternator? I really appreciate this forum! Thank you, Dee

 

Keep in mind to never install the battery in backwards , it will damage the voltage regulator inside the alternator ( not saying it definitely happened to you )

And never overtighten the positive battery post bolt , breaks the special nut underneath it

Positive post in positive direction of car travel , A shop will put it in backwards for you so this is one of the things to witness in the shop service bay with your eyes

The alternator / voltage regular along with the battery can be checked on car or off car at the auto parts store and that would be my first check

Although the fault may not show and be present at the first parts store , drive to the next parts store and on and the fault may show later on the 2nd , 3rd , or 4th

A good alternator / VR will put out 13.5 the 14.5 volts which is above a fully charge battery of 12.75

You can place a tape with a mark on the 12.75 on the instrument cluster and if the fault accures you can quickly glance and get a snapshot with your eyes without distraction from paying attention outside the car windows

If the VR is intermittently failing the voltage gauge will be the battery voltage at that time and it's charge state which may be below 12.75

One thing to watch for is the voltage behavior as the engine shifts and the VR remains stable

This pic is a good running alternator of 14.5 volts and the gauge is very accurate

 

Hi Parker, thanks... I will have to check on the install of the battery and then test both as well as put eyes on the gauges. I will post any update for all to learn about this.. thanks!

 

I put a white tape with a marked arrow pointing fwd on my battery

I'm not the only one to install the battery in backwards and there are some fuses that will pop

 

There is a common thing to happen to the fuel pump commanded to turn off while driving , this would also give you the alternator light

The fuel pump enable is from the crankshaft position sensor seeing engine rotation

This is a crash / safety design

This can fail without a code in the one aspect of the single CKPS signal being used as it is used also for the tach gauge and engine regulation

CEL code P0335

You can command the fuel pump to run at all times with a jumper wire in the aft most and fwd most socket

This will drain your battery with your keys in your pocket so lan accordingly

You do not have a # 2 fuel pump , that is for the V12 and supercharged version

Pics comming



This would be pin 30 to 87 and it may be marked 3 to 5 on later production models

The auto parts store can build you a jumper wire from a tool kit behind the counter , suggect use a blade connector ends on the jumper wire



And then there is the crash switch which can be problematic and not always reset , you can jumper the connector between the 2 white wires leaving the black one alone

This is a pic of a right hand steering model and the switch will always be on the right side by the right door hinge

 

The correct size is
H8
MB88
Group 49

 

I am wondering if the problem is with the battery.
When the engine stalls you will get a battery light
This starting and stalling at the lights sounds more like a possible fueling problem possibly caused by the oxygen sensors. Oxy. sensors do wear out
I have had this problem in both XJ40 and X300 cars. Starts easily after stalling but at next red light it stalls again.
New oxy. sensors fixed the problem

 

O2 sensor Bosch # 13789