Ammeter guage showes discharge
On my 1970 vette when you turn on the blower, lights, or whatever the ammeter will show discharging, for instance as you move the fan switch from low to high the needle goes from a little to all the way pegged, but I have checked the alt. its putting out the right voltage, checked at the batt. with everythig on it shows the 13.8 volts, have driven the car with all lights blower on and after 45 min shut it off and it will start right back up so the system is charging, have replaced the guage with a new one last week still the same thing, anyone had this problem or got a idealas to what it could be?
-
-
Re: Ammeter guage showes discharge
Sounds like a typical bad diode trio. It will show minimal charge with no load but drop like a rock with a load. Check the service manual for a description of how to check it. As I recall, it's a simple check with an ohmmeter on each diode in the trio. -
Re: Ammeter guage showes discharge
Cecil, thanks for the info, the gauge is doing just as you described, the diode trio is located where and what do I look for
Comment
-
Re: Ammeter guage showes discharge
Billy, I am not sure your alternator is charging properly @13.8 volts. (a battery holds more than 12 volts), If you had said 14.5 v or so, probably, depending on battery charge or condition. A quick test is to remove either battery cable (+ or -) after engine is running and if engine shuts off, it is not charging, if it continues to run, it is charging. USE CAUTION, be sure not to touch + batt. cable to a metal ground ANYTIME, this will cause a direct short, for SAFETY reasons, this should be done in a WELL VENTILATED area due to exaust and battery gases. Another test would be to check battery voltage before starting engine and recheck voltage on battery after starting engine, you should see a voltage increase if charging system is working properly, if the voltage reading is the same, it is not charging. HOPE THIS HELPS. SteveComment
-
Re: Ammeter guage showes discharge
Steve, thanks, will try this next time out, but if the system is not charging woulding the car not start after driving with the head lights on high, fan on high for 30 to 45 min., just a couple of weeks ago my daughter was Mrs FRECC a pretty high honer in our small town she sat on the rear hatch in the christmas parade (at night) for 2 hours I had the running lights on and the heater on high the whole time,(gauge showing total discharging the whole time) when we finished the car it stared back up just fine not draggey or anything.Comment
-
Re: Ammeter guage showes discharge
Billy, We would think that the battery should have had a low charge at that point, (AFTER 2 HOURS), however, batterys are different in the way that some will a hold a charge longer than others due to type, rated amperage output, brand, temperature and some natural rechargeability they can produce on their own. SteveComment
-
Re: Ammeter guage showes discharge
Steve thanks again, will try what you mentioned earlier, this is the only problem I seem to be having with it. would really like to reslove itComment
-
Re: Ammeter guage showes discharge
The diodes are located inside the alternator. There are 3 on a heat sink, and 3 in the end frame. Dissasemble the alternator, use a 12 volt test light or a 1.5 volt ohmmeter on the lowest scale. To test the heat sink diodes, connect one test lead on the heat sink frame and the other on the diode lead, take the reading, then reverse the connections and take another reading. Diodes allow the current to flow in one direction only, so if the readings are similar in both tests, the diode is defective. It should read high in one direction and low in the other. If using a test light, it should light in only one direction. Test the diodes in the end frame the same way, connecting to the diode lead and the end frame.
As an alternative, I believe you can take the alternator to AutoZone and they can test it for you.
This test as well as illustrations is in the Chassis Overhaul Manual.Comment
-
Re: Ammeter guage showes discharge
I had the identical problem with my '71. I also concentrated my troubleshooting on the alternator and even put another on with the same result.
The ammeter is in series with a red wire running from the starter to the horn relay. Turns out the problem was a bad connection between the red wire and the horn relay. The system was trying to charge through the ammeter circuit.
RickComment
-
Re: Ammeter guage showes discharge
Billy
One thing thats easy to check that is often overlooked is a loose fanbelt.
BVComment
-
Re: Ammeter guage showes discharge
Would like to thanks everyone so far for their sugestions, the 2 wires that attach to the back of the ammeter are both of those wires suppose to show 12+voltes on my meter when they are unhooked, you konw I ground my meter and touch the stripe one it showes voltage, the other showes the same when i check it. now the ammeter guage which is orginal and I also bought an original style replacement, does it matter which wire goes on which post, I reall don`t think you can plug it up but one way just wondering about that.Comment
-
Re: Ammeter guage showes discharge
Go ahead and hook them up in any order. The Amp Gauge will tell you if it's right or wrong. You got a 50/50 shot! You'll probably get it right the second time.
JRComment
Comment