I have a base model '85 that has had couple of alternators go bad. When the alternators go bad, the battery light does not come on - yet it does come on when the car is cranked over, so the bulb is good. I have two questions. (1) Any ideas on why the battery light is not comming on when the alternator fails to charge the battery? (2) I want to hook up an after-market volt and amp meter since I can't trust the idiot light. How should I wire the amp meter? The instructions say it should be wired in line with the main current draw from the alternator and battery but not connected to the circuit for the starter. Any help would be greatly appreciated. I'm trying to daily drive the car, but the charging system - between slipping belts and short-lived, re-man alternators - has been the only unrelyable part of the car.
As for an amp meter. That is going to require a set of wires heavy enough to go from the the alternator output wire(fat red), to the area where you are going to install the amp meter and back to the connection at the fuse link terminals. And in a way that they won't ground out anywhere. A volt meter can be connected to one of the "bat" battery connectors in the fuse box. Would suggest inline fuse. As for as the volt light. It depends how the alternator fails. This is an "Delcotron" type light. When key is on and engine not turning. One side of the light is fed through ignition voltage. The other to the field circuit in the alternator. Without the engine turning, the field is at ground potential. So the light comes on. When the engine starts turning, the field now is at battery voltage and the light goes out. That circuit is also used to initialize. So if the bulb is bad the Alternator won't "start". As long as the field starts creating something, the light goes out. Even if it is not enough for the loads. If a rectifier trio diode shorts or goes out the light will come on dim. May be hard to see, but it is. It is really turning on and off really fast. Because you would be getting a partial A/C ripple and not a pure D/C ripple. Kind of think of it like, charge, discharge charge, charge, discharge. Every third wave will be negative instead of positive. Or 2 steps forward 1 step back. I would find an aux gauge pod from a GT. Plenty of instructions on how to install on the forum. And it would also give you an oil pressure gauge if you wanted it.
[This message has been edited by cmechmann (edited 11-13-2018).]
What you need is the type of amp meter that connects to a shunt in the line.
This is the sort of thing (just search for Amp Meter on flea bay).
A shunt is basically a very big (to handle the current), very low resistance resistor that goes into the line who's current you want to measure. The resistance causes a VERY SMALL voltage drop. You connect the meter across the terminals of the shunt and it measures the voltage drop and displays it as an amperage.
Sample wiring diagram:
If you wired it so that it did NOT include the starter motor draw, one of these would probably be fine. However I've not tried this and the difference between this solution and a car is that a car can also charge the battery so the current goes the other way. I have no idea if you'd need a different type of shunt based meter for that, dual polarity maybe.
The advantage is that there's no need to run the current bearing line all the way to the meter and back, just the detector lines across the shunt, which should still be insulated, they are connected to the current bearing line though and will still short out it cut/touch an earth but you could also put a fuse in ther as well, near the shunt 'just in case'.
------------------ Anything I might say is probably worth what you paid for it, so treat it accordingly!
Don't buy important parts on ebay or most others online. Buy best ones @ AZ etc. AZ and some others don't need a receipt to get warranty honored. AZ goes by Phone # so keep track of Phone # when you move etc and doesn't care what store sells a part. Unlike PB and some others that will not get warranty in a store for parts sold in another store even if you can find a receipt.
Connect a Volt meter anywhere you what but make sure all power/grounds are good. Engine running should see 14-15V anywhere in the car. This is easy and safe for most people. Fix/clean All grounds in the car. Start w/ See my Cave, Wire Service Should be on a "Hot when running" circuit because meter will add to things draining battery when off like ECM and other standby power.
Amps is a different story... I don't recommend aftermarket amp meters for most people. Several ways to wire amp meter w/o seeing starter motor. Just don't wire big battery cables. But where connected effects what point you're reading. Sometimes you even see negative and positive amps because of where connected. If you only what alt output in amps then connect to big alt terminal. Should only see positive amps there I think.
You need a meter/shut/whatever to handle 100a or more. Need to be rated higher then alt power output. But meter may never see that because many cars doesn't use all power available.
Caution: Added Shuts often have problems in automotive uses because not made for this use in the long term like shuts w/ iffy connections can F up alt regulator etc. Plus if not installed carefully then can have same problem as heater blower resistors... IOW they can get very hot and even cause fires. Is why most high current shuts have little or no insulation.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
The ammeters on my home auxiliary panel for 7000W 220V back up power use current sensors. They are just an induction coil in a donut shape and the output goes directly to the meter. Same principle as the clamp on ammeter.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
AZ and some others don't need a receipt to get warranty honored. AZ goes by Phone # so keep track of Phone # when you move etc and doesn't care what store sells a part.
Autozone wanting my phone number is exactly why I don't buy crap there.
Years ago (1990-2000) I had a '73 mach 1 that I installed a 5.0 FI in......And a whole bunch of other mods.....I had a Haynes manual that covered all of the 1st gen Mustangs...It had different wiring diagrams for the different years.....There was >>>THREE<<< different ways that the Amp gauges were wired in the different production years.....I thought that was simply idiotic!
Years ago (1990-2000) I had a '73 mach 1 that I installed a 5.0 FI in......And a whole bunch of other mods.....I had a Haynes manual that covered all of the 1st gen Mustangs...It had different wiring diagrams for the different years.....There was >>>THREE<<< different ways that the Amp gauges were wired in the different production years.....I thought that was simply idiotic!
I've never trusted a Haynes manual. I've read so much contrary info in them that just hearing the name anymore gives me an upset stomach. Your better off listening to an Klingon Field Mechanic, in my opinion.
Spoon
------------------ "Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
I've never trusted a Haynes manual. I've read so much contrary info in them that just hearing the name anymore gives me an upset stomach. Your better off listening to an Klingon Field Mechanic, in my opinion.
Spoon
I tried that, but they are hard to find and then he wanted too much up front before answering my questions.........(And, considering the Fiero comic I just drew, interesting coincidence) .....
Sorry for the late response - medical stuff had me down for a bit. Thanks for all the good information. Sounds like the amp gauge may cause more issues than its worth. I have a GT gauge pod I can hook up to see if the volt meter in that gives me enough warning of a bad alternator. I don't know if my real problem is an issue with my electrical system or the poor quality of the re-man alternators (all but the first one have been warranty replacements from AutoZone). I'll also check the grounds again just to rule them out. Thanks again.
Originally posted by Dennis LaGrua: The ammeters on my home auxiliary panel for 7000W 220V back up power use current sensors. They are just an induction coil in a donut shape and the output goes directly to the meter. Same principle as the clamp on ammeter.
Sense Coils require AC power and won't work on DC. You can get sensors that read DC amps but cost more and/or harder to use most of them in an engine bay. Shuts are used for most or all aftermarket amp meters for cars. Some vehicles have shuts on/near battery as OE part from the factory to monitor amps to/from the battery. Example:
CLICK FOR FULL SIZE
Dash doesn't show amps but PCM/BCM monitors amps. (Can get "amp clamp" meters for DC using Hall Effect chips but cost more. most used clamps at flea markets etc are AC only.)
[This message has been edited by theogre (edited 11-22-2018).]
Originally posted by Lambo nut: Autozone wanting my phone number is exactly why I don't buy crap there.
Yet you pay most anything w/ CC/DC and/or likely use loyalty cards that track you and many stores/sites won't honor part marker's and other warranties w/o being a big pain in the ass.
I use AZ for years and never call me. I only give P# when buying important parts. Buying whatever like light bulbs and doesn't even ask me for P#. I have replace a starter under AZ warranty after 20+ years of use w/ nothing but old P#.
[This message has been edited by theogre (edited 11-22-2018).]
Originally posted by Bruce8524m: Sorry for the late response - medical stuff had me down for a bit. Thanks for all the good information. Sounds like the amp gauge may cause more issues than its worth. I have a GT gauge pod I can hook up to see if the volt meter in that gives me enough warning of a bad alternator. I don't know if my real problem is an issue with my electrical system or the poor quality of the re-man alternators (all but the first one have been warranty replacements from AutoZone). I'll also check the grounds again just to rule them out. Thanks again.
Volt meter is good or better because most came remember engine running = 14-15v. Amp meters doesn't have a single value saying when electrical is good or not because only read amps used at a given time. AC and others can have amps changing as normal operation like when have DA6/HR6 clutch switching on/off. Amp will change but when you see those changes on a Volt meter then look for iffy grounds and other problems.
Even if several alt's dies, Can be a symptom not the root cause... Iffy Ground(s) isn't only thing that can kill the alt. Iffy battery and battery cables can kill alt, starter, etc. Any Iffy wires to dist "box" under C500 can be problems too. Alt's wires and/or alt brackets will cause problems. Main + is splice to red wire to side and smaller wire goes bad at either end. Battery light and wire to it can go bad. Brackets are the Ground to the alt case.
"dead" battery can fry alt's too. Car battery is Functional Dead at/under ~11.5 volts. You start/jump the car and low battery can/will draw a lot of amps from the alt and overload it. SI alt's have no protection for this. CS alts won't turn on for this but jumping etc can fake it and turn on.
You can test a car w/ a amp meter to see if you have more amps used by whatever but not install one in the cars. Follow same in See my Cave, Battery Leaches If possible borrow/rent DC amp clamp for testing w/o disconnect or cutting to insert a shut meter. (Most 10-20a range meters have a shut inside.) If you added/"upgraded" HL, Sound, etc, then maybe now car needs a heavier alt. See my Cave, Watt Story and rest of section. Old SI users can upgrade to CS130 w/o much work and get higher output for same engine power used.
[This message has been edited by theogre (edited 11-22-2018).]
