My 1997 jeep grand cherokee tsi with a 5.2 seems to have a charging problem. the alternator is a year old and was tested twice in the last week at 2 different locations and was shown to be good. same thing with the battery. the problem is the voltage drops suddenly and it is the same symptoms as a dead alternator. this happens intermittently and will be fine for a week and then happen twice a day for a few days and then ok for 5 days. any ideas on what to check and how to determine if the part is bad. btw, i have cleaned and tightened all the connections around the battery, alternator and the ground on the body.

I ran into this problem with my 97 grand 5.2 a couple years ago. After2 weeks and a little over $500(replaced alternator, changed fan belt, charges for diagnostics from dealer, etc), I decided to look at it agian myself. Had my wife start it while I was standing on the driver side. Noticed when looking at fan belt that it didn't look in line, looked like it was leaning toward the front on drivers side and the belt was vibrating.
I pushed on the front of the power steering housing and it moved back! Not much, but more than I thought should. Found out that the power steering mounting bracket was cracked in a couple spots(this after I removed the pwer steering unit and the mounting bracket fell to the ground in pieces!) , didn't have to unhook any hoses, there was just enough room to be able to remove the mounting bracket. forty five dollars later(new bracket from dealer!) and about 30 mins both removal and installation, and problem solved. Never had a problem since!

How is the pigtail ground strap from engine block to body? Have you had engine diagnostic test done? Voltage rVOLTAGE DROP TEST
A voltage drop test is the only effective way to find excessive resistance in high amperage circuits. It's a quick and easy test that doesn't require any disassembly and will quickly show you whether or not you've got a good connection or a bad one.
To do a voltage drop test, you create a load in the circuit that's being tested. Then you use a digital volt meter (DVM) to measure the voltage drop across the live connection while it is under the load. Voltage always follows the path of least resistance, so if the circuit or connection being tested has too much resistance some of the voltage will flow through the DVM and create a voltage reading.


If a connection is good, you should find little or no voltage drop and see less than 0.4 volts for most connections, and ideally less than 0.1 volts. But if you find more than a few tenths of a voltage drop across a connection, it indicates excessive resistance and a need for cleaning or repair.
CHECKING THE STARTER CIRCUIT
To check the starter circuit for excessive resistance, you need to measure the voltage drop at the battery, battery cable connections and starter while the engine is being cranked.
The first check is "available battery voltage." For the starter to crank at normal speed, the battery must be at least 75% charged (12.4 volts or higher). Low battery voltage can not only affect the starter but every other electrical system in the vehicle.
A. Set your DVM to the 20 volt scale, then connect meter positive (+) lead to battery positive (+) post (not the clamp or cable), and the meter negative (-) lead to battery negative (-) post.
B. Disable the engine so it will not start when it is cranked. (Ground the ignition coil wire, or disable the ignition circuit or fuel pump relay.) Limit cranking time to 15 seconds or less.
C. While cranking the engine, record the volt reading on the DVM. D. Next, connect your meter positive (+) lead to the battery terminal stud on the starter, and the meter negative (-) lead to the starter housing.
E. While cranking the engine, record the volt reading.
F. Compare the two voltage readings. If both are the same, there are no excessive voltage drops on the positive feed side.
G. If available voltage at the starter is not within one (1) volt of battery voltage, there is excessive voltage drop in the circuit.
The next test is for voltage drop on the positive side of the starter circuit.
A. Make sure the battery is fully charged.
B. Disable ignition.
C. Set DVM on 2 volt scale.
D. Connect meter positive (+) lead to positive (+) battery post, and the meter negative (-) lead to the battery terminal stud on the starter. While cranking the engine, record the voltage reading.
The maximum allowable voltage drop including the solenoid or external relay in the starter circuit should be 0.6 volts or less.
If you find more than a 0.6 volt drop in the starter circuit, you can isolate the bad connection by using the following voltage drop tests.
* Check the positive battery post and cable connection by measuring the voltage drop between the two while cranking the engine. Connect the meter positive lead to the battery post and the meter negative lead to the cable clamp. A good post/cable connection should have zero voltage drop.
* Check the positive battery cable by measuring the voltage drop end to end while cranking the engine. Connect the meter positive lead to the clamp on the positive battery cable, and the meter negative lead to the end of the cable at the starter. Crank the engine and note the voltage reading. A good cable should have a voltage drop of 0.2 volts or less.
* To check the starter solenoid or relay connections, connect the meter positive lead to positive battery terminal on the solenoid or relay, and the meter negative lead to the starter motor terminal. Crank the engine and note the reading. A good connection should have a voltage drop of 0.2 volts or less.
Next, you need to check the negative side of the starter circuit. To check the entire circuit, connect the meter positive lead to a clean spot on the starter motor case and the meter negative lead to the negative battery post. Crank the engine and note the reading. The voltage drop on the negative side should be 0.3 volts or less.
If the voltage drop is too high, set your DVM to the 2 volt scale and start checking each connection on the negative side to find the bad connection or cable. Use the DVM leads to check across each connection while cranking the engine as before.
Check the negative battery post/ground cable connection (should be zero voltage drop).
Check the negative ground cable from the battery to the engine (should be 0.2 volts or less).
Check between the negative battery post and starter housing (should be 0.3 volts or less).
Check between the engine block and starter housing (should be 0.10 volts or less).
CHECKING THE CHARGING CIRCUIT
To check the alternator connections on the positive side for excessive resistance:
A. Set DVM on 2 volt DC scale.
B. Connect the meter positive lead to the alternator output stud (B+ terminal).
C. Connect the meter negative lead to the positive (+) battery post.
D. With the engine running at 1,800 to 2,000 rpm with all lights and accessories on (except the rear electric defroster), check the voltage drop reading. It should be 0.5 volts or less. If higher, the connections between the alternator output stud and battery need to be cleaned. Also, look for loose connections or undersized cables.
To check the alternator connections on the negative side for excessive resistance:
A. Set DVM on 2 volt DC scale.
B. Connect meter negative lead to alternator case.
C. Connect meter positive lead to battery negative (-) post.
D. With engine running at 1,800 to 2,000 rpm with all lights and accessories on (except rear defogger), check the voltage drop reading. On the negative side, it should be 0.2 volts or less. If excessive, the connections need cleaning or the negative cable needs to be replaced. Some alternators are mounted in rubber bushings and have a separate ground strap. If so equipped, be sure to check the voltage drop across this strap, too.

egulator checked with voltmeter?