This applies to a 1994 vehicle with the 3.3L engine. (The 3.8L version should be the same, but the 1996-onward installation may be worse.)
You need a service manual, though I may include brief pointers from it to make this advice more cohesive. Study the manual, including Fig. 5 showing the terminal to wiring block you have to move to the replacement alternator.

Changing the alternator on the Chrysler 3.3/3.8 litre engine is very awkward. Be prepared to go under the vehicle, to work down the back of the engine, and to take off more than you expect.

So you want to be sure of the diagnosis before you start. The alternator is controlled by the engine computer, which should set a fault code, but that may take a while to get set. In my first I had a code 41, problem with control circuit, rapping the side of the alternator with a wrench restored function every time. I then checked the voltage gage in the instrument panel, but had to check with a hand-held meter as the gage is difficult to decipher (you think that it is 2 volts between marks, but count the marks between 8 and 18!) and not consistent in scaling (seeming to have at least .25 volt hysterisis). It does seem that the marks you'd expect to be 12 (battery close to charged) and 14 (approx charging voltage of typical system) are roughly that.

PREPARE yourself with:
- 7, 8 10, 15 deep & shallow, and 18mm deep sockets - if taking alternator apart, a medium screwdriver for JS standard heads (Phillips will work if the tip is blunted and you are careful), and desirably a 10mm deep socket.
- 3/8" ratchet wrench with short extenders and adapter to 1/4" for the small sockets (preferably also a 1/4" drive ratchet for shorter swing clearance and shallower head), desireably a 1/2" ratchet wrench or quite long 3/8" for leverage on some bolts/nuts
- diagram of serpentine belt routing
- light wire or heavy twist ties or such to hold belt up, and PS reservoir out of the way of getting bracket bolts out
- opera gloves (well, snug-fitting covering for your arms, as they'll contact dirty pieces reaching in to get at bolts, I wonder if small sizes in those defective Lulemon yoga pants are available?).
You will of course have to remove and reinstall the serpentine drive belt - go to my belt replacement page to see my advice on that, and needed slim tools.

My vehicle has a Denso 120 HS alternator, commonly referred to as 120 amp but specs show 102. (It's in what is called the "120" family, there is a smaller "90" family, one distinguishing feature is the lugs for the ground connections don'ts stick out as far on the 120. (There seem to be several variations on the manufacturer's name, especially the prefix such as Nippon, mine had ND on the end cover (Nippon Denso) but the wiring diagram in service manual calls it something else - though see my wiring diagram errors page for errors.) If trying to swap from another vehicle model, note the pulley has to match the belt ("6-rib" in this case

You might consider replacing the tensioner for the serpentine drive belt though it is another $80. or more cost, you have to take it off anyway. If you have time/alternate transportation to go get one if needed, you might examine it - I found the old one had taken a set relative to the new one (the mechanism and pointer were significantly CW from the new one which appeared to be at fully extended position). I purchased a new one because in reinstalling the belt previously the old one had stuck in a retracted position so the belt was loose, until I whacked it with a wrench. It was more difficult to get the belt back on with the new one, given the limited tool travel I describe in my page on the belt.
And consider a new belt.

Think through sequence carefully, especially involving the tensioner and PS pump reservoir with its line, as they get in the way of other work.

Looking at the service manual instructions, I make these recommendations:
- With air conditioning and the 4-speed AT (thus a transmission computer on the firewall) you definitely have to remove the big "generator support bracket", there isn't room to slip the alternator aft and up. That requires removing the belt tensioner, removing one bolt of the right engine mount, and removing three bolts holding the PS reservoir and tubing. Removing the tensioner may necessitate removing a brace from the rib the PS pump and alternator attach to.
(See the bottom of this page for a possibility of rotating the engine, which is not easy either.)
- consider holding the serpentine belt up so you don't have to spend time later getting it back around the several pulleys and idlers, though it's a fiddling bother to do so especially avoiding swing of belt tension relief tool.

- but first undo the tensioner stud nut (see below), as moving the tensioner outboard that lets you get at the PS tube clamp bolt and the lower bolt of the big "generator support bracket", and the stud goes through that bracket.

- You have to undo three bolts to move the power steering fluid reservoir, counting a hose clamp lower down. (8 mm socket.)
- once you remove the top alternator attach bolt you may be able to swing the alternator forward to easily remove the nut holding the wiring loom clamp to the alternator, and pull the alternator back to more easily get at the other wiring nuts, and get at the bottom bolt (you might have to loosen the nut a bit - 15mm socket on nut and 15mm wrench on head).

- GENERATOR SUPPORT BRACKET (refer to figure 8 in section 8B of service manual text):
> Note the "generator support bracket" goes on the inboard side of the cast rib structure, held to it by the tensioner mounting stud (oversize hole) whereas at the three side mounting bolts it is on the outboard end of the engine.
> the forward-most of three bolts (top) attaching the tall "generator support bracket" to the right side of the engine goes through an angle bracket to an engine mount. A deep 18mm socket is needed. There is a spacer between it and the "generator support bracket", to fall out and get lost - the bolt is long.
> the long black bolt is the top generator attachment, the shorter three hold the bracket to block and manifold. long, the lower one short
> and there's one bolt on top holding the bracket to the intake manifold

> Then you can get good access to the bottom bolt of the alternator, the very long one. At that point, I suggest removing the terminal block from the alternator while it is still supported (8 and 10mm sockets). (Going back together, you can put the bolt in place but not fully tight until the "generator support bracket" is installed - at which point it is awkward to work on to tighten, as you have to have a socket wrench on both ends (deep socket on outboard end where the nut is).
> Note that the bolt does not squeeze the two alternator lugs together, which could crack them - there is a press-fit spacer that slides in one lug to take up slack (the replacement alternator should have the spacer backed out somewhat to accommodate tolerances).

- TERMINALs > The wiring diagram in the factory manual shows the terminal block flipped upside down. Not essential to understand geometry as you don't need to work on it until you have a good view with other pieces out of the way, unless you need to diagnose where the fault actually is before undertaking this painful job. (The wires off the studs of course actually come out of the back of the terminal block as the wiring harness.) Examine the alternator internal diagram to understand what the wires are for (hot stud A11 includes a filter capacitor to ground, you have to make sure you get the right stud if grounding the field to test control). The wiring harness comes from forward on the engine somewhere to the terminal block, with branches to a 4-contact square connector near the firewall (probably the heated oxgen sensor which gets ground from the alternator) and a rectanglular connector TBD near the firewall.

The tensioner has a projection from its mounting face that goes into a slot in the cast structure to position it in rotation. I suggest jamming something between the tensioner and the frame once you get it rotated correctly, to ensure it stays there while you go underneath to put the nut on.

> Yes, you'll need to go under the vehicle to get at the tensioner stud retaining nut. You can reach past the sharp manifold-exhaust joint, under the alternator, using a 3/8" ratchet with shallow 15mm socket, handle aft. Relatively speaking that is far easier than trying to get your arm far enough down the back of the engine past the junk there (if you can tilt the engine forward, going down the back might be feasible - to tilt the engine in my 1994 vehicle would require removing parts from engine/radiator to get clearance).
> You may need to remove the cranked heavy metal bracket that runs horizontally off a manifold bolt to brace the rib, to get better access to the tensioner stud nut. At the manifold, inboard you'll need a deep 15 mm socket as the stud is long. For re-installation, note the captive spacer is on the inboard end. The service manual shows the bracket. However, the outboard end of the bracket tends to hang up on the PS pump hose. You also need to have the generator in its normal position, as when fallen fully down it prevents lineup of the bracket's outboard bolt.

Better access:
- If you could move the A/C lines on top of the shock tower that would really help work on the side to remove the "generator support bracket". Perhaps you can get an A/C shop to do that next time your A/C is serviced, in case bending them causes leaks.

- To improve access down the back of the engine, disconnect the square connector to alternator/oxygen sensor, the connector to the MAP sensor (that sharp-cornered plastic box on the back of the manifold), the vacuum line to the PCV valve, and the ground strap to the firewall

- You may be able to pry the engine forward a bit and put a block between it and the firewall.

- An article on AllPar web site advises to take out the front engine mount bolt by the radiator, and let the engine rotate forward - but it looks to me as though there is little clearance from engine to radiator fan and other proximities. There's something in that claim about parking brake and Park transmission selector position but it is garbled. Sounds tricky, as there is more than one bolt and multiple pieces in the service manual's instructions - perhaps the mount can simply be dropped from the front crossmember. The service manual cautions to support the engine to prevent rolling forward, and advises the RH mount is adjustable by about 2/3 inch but that seems tricky. However, such may be just as much work as removing the "generator support bracket".

Take photographs during disassembly.

If you try to test diodes, beware that not all meters work on them. My fancy Innova automotive meter does not, whereas the diode setting on a low-priced Sperry Pocket-Pro DM-21 does. The diode set itself is a wild affair, hard to see where internal connections go especially covered with insulating paint, the tabs the diode leads are welded to are L-shaped, with a leg going into a bridge device that somehow connects to the output terminal.

The output stud's plastic protection shroud is held on by a nut that requires a 10mm socket (same nut thread as the one that holds the lead on but that nut takes an 8mm socket).

The armature terminal nuts take a 7mm socket. I get about 3 to 4 ohms across them (which is brushes plus armature).

Resistance between stator leads is very low, hard to measure. There are four leads, which gives less ripple.

See my wiring diagram errors page for errors. I don't see where the output capacitor is, I presume the device across the armature (perhaps a capacitor) is inside either the brush block or the associated other block that partly supports it.

In my alternator there is an unused threaded lug on the diode set, near the brushes, and an used screw on a lug held by one of the nuts holding the cover on. (The design is widely used.)

© Keith Sketchley Page version 2016.03.20 (1950PST)

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