Driving my '89 XJ6 today and got about 3-4 miles from the house, power went way down, all dash lights went off, and I slowed to a stopped; dead, no power. I figured a battery, because it is a very old battery and it was dead last week. After getting a little charge, I started the car up, removed the pos cable off the battery; car dies. I figure alternator but I don't want to just rush. I also want to make sure if I replace the alternator, is there anything else I should do/check? Could it be anything else? I have found reman units from $60 to $260. Difference? Some put out more amps than others. Is more better? Thanks!

 

Before you buy either a new battery or alternator, check to be sure the alternator belt is still there and appropriately tight. If the belt looks good, there are some easy tests you can run if you have a DC/AC voltmeter. The tests include battery voltage after discharging any surface charge, battery voltage while cranking, alternator charging voltage, voltage drop between the battery positive terminal and alternator positive terminal, voltage drop between the battery negative terminal and alternator case, and AC voltage ripple across the battery terminals (a means of determining diode health). If your meter can test diode function you can also check the diodes directly. There are plenty of good YouTube videos that explain how to conduct these tests to determine whether the problem is your battery, alternator or something else.

Regarding disconnecting the battery while the engine is running, that practice has been prohibited since the advent of electronic fuel injection. Here is a warning from page 75 of the XJ40 Technical Introduction manual:




Hopefully your dump module is working properly or your electronics may have been damaged.

Please keep us informed.

Cheers,

Don

 

Wow, I had no idea that something like just disconnecting a batt cable could do harm! Thanks for the information. It just shows that my old time knowledge is very outdated for modern cars. This is not the first time I've discovered what I thought I knew was good information about cars, wasn't. My electronic dash info center (square info display on right side) has not worked since I got the car. First it was only partially (half) working with unintelligible info, now, it has stopped completely. The car seems to run fine, but not having all the info makes me uneasy. I like to trust the gauges, but it is hard to when you know there are problems with the display. Example; My oil pressure gauge works...most of the time. I have chalked it up to a loose wire on the sending unit since it is an intermittent problem. The same goes for the voltmeter display. It would give me a discharge (red) reading, then in a few seconds, no problem. I have thought it was probably just the solder problem that these electronic displays have and I have bought a solder kit to try to remedy the problem. I have never really soldered before, so I'm unsure of how to proceed. I've been watching videos about soldering, and read on this forum about the problem, but is there any other thing I should be aware of? As a complete novice, do you think I should even attempt? I have taken care of the more pressing issues; new steering rack, complete brake rebuild, engine oil leaks, etc., and these other items didn't seem as urgent but they are urgent now. Thanks!

 

As far as alternators go,stick with something at or just above factory amperage unless you have a high output stereo with an amp or have added some other high draw electrical accessory. Buying new would be better than rebuilt but it all depends on your budget. Some rebuilt units come with a good warranty too. The choice is yours.

 

Here's a link to a new 90 amp alternator. It's $170 new,comes with a warranty,no core required and delivered to your door in 2-3 business days.

NEW ALTERNATOR FITS 1987-1989 JAGUAR XJ6 3.6L 0-120-469-810 AL191X 0-986-037-040 | eBay

 

The most common cause of significant fluctuations in the oil gauge is the oil sender itself. You might try cleaning the electrical connector if it's been contaminated with oil, but the transducer itself commonly fails or loses its ground connection to the block due to oil ingress into the mounting threads.

Could this be related to your suspected alternator problems?

The solder joints in the early displays are a well-known problem. With your skills you can definitely learn to solder, but I would recommend you practice on some old broken electronics before you work on your instrument cluster. The main recommendations I can offer are:

1. Use a soldering iron between 15 watts and 25 watts. Never use a soldering gun on electronic circuit boards because the temperatures are too high and the risk of damage too great.

2. I recommend a flat screwdriver-shaped tip for your soldering iron about 1/8 inch wide rather than the sharp pointed type of tip. The reason is that the wider tip allows you to simultaneously apply heat to both the copper pad on the circuit board and the wire lead of the electronic component (resistor, capacitor, transistor, diode, etc.).

3. If your soldering iron is new, clean and tin the tip prior to attempting to using it.

4. All items to be soldered must be clean of any grease or other contaminants. Use a small brass brush and contact cleaner spray to clean components.

5. Do not attempt to solder anything until the iron has reached full operating temperature.

6. Many electronic components are heat sensitive, so the goal is to heat the solder joint to melting temperature as quickly as possible, apply just enough solder, then remove the tip of the iron and allow the joint to cool naturally, without blowing on it or cooling it in any other way. Attempting to cool the solder too quickly will cause it to crystallize, causing a "cold" solder joint with reduced electrical conductivity and increased risk of cracking under vibration. And any vibration while the solder is cooling can cause a cold joint.

7. When re-flowing old solder joints, heat the joint until the solder melts, apply just a little fresh solder, then allow to cool.

8. Too much solder can be worse than too little. It can lead to a weak joint or the blob of solder can touch other components and cause a short.

That's all I can think of off the top of my head. Practice on an old radio or cassette player or such and you'll get the hang of it.

Cheers,

Don

 

maybe practice on an Elcaset or an 8-track?

 

Is there a way to visually inspect the solder joints on the instrument cluster to determine which are bad/good or should I just assume all are bad? I think I read somewhere where the person inspected the joints first and could see cracks in the solder. Opinion?

 

Yes, you can sometimes see cracks in poor solder joints though it may take a magnifier to see them. Often you won't be able to see any cracks but the solder will have a "frosty" appearance instead of a shiny chrome-like appearance.

The photos at the link below may give you some ideas of what to look for:

Transmission Control Module Repair

Cheers,

Don

 

I bought a new battery since the old one was very old and I could never trust it. After installing it, I hooked up my cheap (free) Harbor Freight multi meter to see what the voltage was doing and started the car. The battery read 14.4+ volts with no load, and then when I turned on the headlights, it read 16.4+ volts, which means the alternator is OK..... right? The volt gauge also now reads OK. Could just replacing the battery make a difference? Maybe I have a loose wire of component somewhere? I checked the connections on the alternator and they seem to be OK. Could there be a bad ground? Intermittent problems are always the worst! I still have not done the other tests you have suggested.... it started to rain, but that is where I'm at so far.

 

14.4+ volts is good for the alternator output, measured across the battery terminals while the engine is running. 16.4+ volts is too high and may indicate that the voltage regulator is not working properly.