Question-------------------------
Followup To
Question -
-------------------------
Followup To
Question -
-------------------------
Followup To
Question -
My brother has this '87 S-15 4x4 truck,2.8 litre,auto.,p.s.(currently unhooked),a.c. His truck died the other day when he turned the headlights on,it will also die when he turns on any of the following:running lights,heater,dome light,windshield wipers,or radio.Also with the key off,the headlights will not come on.He has a new battery and he said he changed the alternater with a good one from a junk yard.I know he good still have a bad one but he says he knows for sure it is good. The p.s. is unhooked because it keeps breaking the aluminum bracket.I'm guessing a dead short,possibly in the ignition switch inside the column? Do you have any ideas,This is his only transportation and its in my garage.Any help will be greatly appreciated.
Answer -
NEVER EVER install junk yard parts, especially electrical parts in a computerized vehicle. You have no way of being POSITIVE that this used part is good or not.
An internally shorted electrical used part can cause SERIOUS damage to any and all electronic components within the vehicles electronics.
HOW does he know the alt is GOOD ?.He checked the output with volt/ohm meter.He said it was putting out.12.5 volts.The original alternater was purchased about 6 months ago.
Did this problem occur BEFORE the alt and battery change ?.Battery was changed about a month ago.He changed the alternater thinking it was the problem. The problem just started about a week ago. The alt. he put on it is the one he checked with the meter.
What is the past and current repair history ?.The truck has over 100,000 miles on it.Nothing major has ever been done to it. New water pump about a year ago.Alternater about 6 months ago.New battery about 1 month ago.new distributer cap,rotor, and plugs about 2 months ago.He has owned the truck for about 3 years.Previous owner was our great-aunt,She bought it new.She kept excellant care of it,maintaning regular maintenace and kept all records from a GM garage.The truck is still in good shape.Was running really well until about a week ago.This problem was just all of a sudden.Didn't seem to give any warning signs.He had drove it home,shut it off,everything was fine.Started to leave that night,went out and started it,turned the headlights on and it died.Turn the lights off and it will restart.Turn lights back on and it dies.Then he started it,left the lights off, turned heater on,truck died.turned heater off,restarted truck, turned radio on,truck died. Also,in order to restart truck, you have to turn key all the way off before trying to start it.
autohelp
Answer -
Normal alternator OUTPUT with the engine running is 13.8 to 14.2 volts . What is the AMPERAGE output ?.
I would FIRST make SURE that the alternator is functioning properly. The readings you gave me are NOT CORRECT.
Remove the alternator and take it into any auto parts store such as AutoZone, Checkers, NAPA or similar and they will test it for you for free. I would also take the battery with you and have it tested as well.
Once we get the charging system working, THEN we can continue.
He just got back from Auto Zone.Alternater is 14.38 volts & 68 amps.Diode is also good. Battery 550 cca and is also good.
autohelp
Answer -
OK, Install them in the vehicle and let me know what the charging volts are when measured at the battery .
The alternator should get quite warm to the touch after the engine has been running for 15 or so minutes, Does it ?.
When the engine is at normal operating temperature and if you note the engine idle speed, As soon as you turn ON the headlights the engine rpm's should drop slightly, Does it ?.
Found out those results was while on the vehicle.The alternater does get warm.Your third question confuses me slightly.As soon as you turn the headlights on,it kills the engine.There is noway to check for a slight drop in rpm.It also kills all power to the dash immediatly.
autohelp
AnswerOK, What your telling me is that when you start the vehicle the engine WILL RUN. If you turn on ANYTHING electrical the engine quits.
Are you absolutely positive that this truck does not have or HAD some kind of theft deterrent system in it at one time ?.
The ONLY other possibility is that there is a fault within the electrical ignition switch that is mounted under the dash on the left side of the steering column.
I have seen hundreds of off the wall electrical problems but this one is one of the top 3 that is very interesting.
Make SURE that the battery GROUND cable is securely attached and tight where it is bolted to the engine block.
Make SURE that the battery POSITIVE cable is securely attached and tight at the starter post.
On the NEGATIVE battery cable where it attaches to the battery there should be a smaller black wire that has a round end on the end of this wire and it should be attached to a good ground source like on the inner fender panel right near the battery.
Also there should be a smaller RED wire that is connected to the POSITIVE battery cable at the battery post. This smaller RED wire attaches to the BAT terminal ( there is usually a RED plastic cap) where this RED wire attaches to the alternator.
Check these and let me know.
If everything checks out OK, Then I would look at the electrical ignition switch as said above.
Let me know.
autohelp
