# 89 ford probe electrical problem



## jmstapleton14 (Apr 21, 2007)

I have a probe that i just bought with the given information that it had a problem with the alternator, as it is driveable but the battery drains. where once i got it home and took it to two places and got home it wouldnt start until i jumped it. as its a digital gauge, it usually is at 4 bars and slowly drains to two bars then wont start. i took the alternator out and took it to an auto zone where there test said it was good. odd enough once i started it after it sat for a day dead the alternator smoked... they believed there was just foreign debris in the part, which i did notice a leaf actually... so i took the part and put it back in, then took the battery out as well as another like battery to the autozone where the original was just reading as low and needed a charge while the second was good, after leaving the battery to be charged there i came back to pick it up and found that they had apparently tested it and it was good as well. putting either battery back into the car it now runs yet again but the battery still drains. what could it possibly be? they stated it could possibly be the voltage regulator.. which to my knowledge is typically a box on the alternator but there isnt one on this particular one. so im stumped at whether the alternator is actually bad beyond the "test" done or its a wire at fault.:4-dontkno bytheway i know these cars are general mistakes at fixing but they are great drives....


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## qldit (Mar 26, 2007)

Good Morning jmstapleton14, although your problem could be caused by some device in the vehicle which is drawing power continuously, I suspect your alternator may have a problem.
What commonly happens is that the rectifying diodes in the alternator operate perfectly and the battery is charged normally during engine running.
These diodes get hot and actually breakdown internally because of that heat, the symptom is quite heavy battery drain and the battery will be drained in ten or fifteen minutes or so.

To analyse this problem, carefully disconnect your battery terminal and disconnect the main alternator wire at the alternator, carefully insulate that disconnected terminal on that wire.
Charge your battery and then reconnect your battery.
Observe if the problem still happens, don't do any night driving because the headlamps have quite heavy drain.

If the discharge problem is cleared, replace your alternator diodes or replace the alternator.
You should get at least a normal days driving simply running off a fully charged battery.

Other possible low current disharge paths can be a lamp in the boot being permanently illuminated or a starter motor solenoid with heavily contaminated internal heavy contacts.

Personally I would suspect that alternator is your problem, the usually bench-test OK but disguise the problem when they are cold.

Cheers, qldit.


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## jmstapleton14 (Apr 21, 2007)

morning qldit, Thanks for getting back to me of your belief to the problem.. but im left with a few questions of your help. first can you tell me which of the wires connected to the alternator is the main one. i would assume youve worked this particular type, but theres the smaller wire that connects via connector and bolted to the alternator or the plug in connector which i would assume is the main but..... from your statement of "insulate" the disconnected terminal, which im kinda lost of, i would think its the actual open wire on the alternator. so how do i insulate that terminal? I understand why i should disconnect the battery THEN the terminal, but are you saying that i leave the terminal disconnected then run the car? while if the battery still drains then the problem is exactly as you described? Elsewise you described most of what its doing to a tee. though i dont understand the two other possible problems(starter solenoid and "lamp in the boot")as i really dont know all that much of electrical problems and wasnt thinking of that in buying this vehicle. as i was told that some college guy going for a degree in automotive work diagnosed this vehicle as needing an alternator and that was all that was said... well i hope you can further help me with this situation. good day mate, jmstapleton14


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## qldit (Mar 26, 2007)

Good Morning jmstapleton14, yes what commonly happens is that when the alternator (diodes) is hot they still operate as rectifiers to charge the battery when the engine is running but act as a discharge path when the engine is stopped, so the battery discharges back through the internal windings when the engine is stopped.

I suspect that could be why you saw smoke in that area.

This is usually quite a heavy disharge and commonly completely flattens the battery, wherupon the diodes cool and then appear OK or test as being normal.

The alternator normally would have a plug which is associated with the internal regulator system and a terminal with a nut, this is for the alternator output and feeds directly to the battery, so it remains powered at all times.
This is how I suspect your discharge is happening and is the reason for disconnecting the battery before disconnecting that terminal. 
I usually simply shove a bit of plastic tubing over that disconnected terminal on that wire to ensure it does not touch any earth point, otherwise it is the old "one flash and your'e ash" story.
So the machine and systems should operate quite happily on a charged battery without that alternator connected. (you may show a red CHG light on your panel)
If you had an ammeter you could connect it inline and test at shutdown after some heavy use, but the simplest method is to drive the car without that lead connected so that you can prove that the discharge is no longer happening.

With boot (you call them trunks) lamps remaining "on" the discharge happens over a much longer period, like 20 hours or more, often these are operated either by a mercury switch or a mechanical switch near the boot hinge that can hang up, but that problem is usually quite intermittent.

With starter solenoids the continuous day to day use and discharge path is much less likely, but what happens is that a buildup of metallic contact material off the heavy solenoid switch, builds up over time gradually on the surface of the internal switch area and can cause a lower resistance path to happen where the battery can gradually discharge through that material, this is not common but I have found it on a couple of occasions after prolonged use. (many years) 
It can also cause low ignition coil voltage in some vehicles because in some of the older vehicles there was a separate lead from the starter to the ignition coil to bypass a coil series resistor during the start sequence. I doubt if your machine would use that principle. So that point is only for info.

I would shoot for the alternator! 

Cheers, qldit.


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## BUDFAN8 (Apr 11, 2007)

when they test your alternator at an auto parts place it will get alot more power and amps to it than it will being in your car therefore it will put out more. i do not trust thier machines they use testing them. i have seen it happen more than once where they test one say its good and it still be bad.


check the single wire bolted to the back of the alternator make sure there are no bad places or corrosion on it. if it looks ok make sure one of the wires in the plug is hot (use test light or multi meter) if that is good get a new alternator or have your old one rebuilt. if the car can be down for a few days i suggest the rebuild its alot cheaper.


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