I have a 96' 2500 the truck will not charge. The codes read low voltage supply to ASD relay. What is it, and what is needed to fix it

 

The code can be generated by a faulty battery temperature sensor, a bad PCM, or a bum alternator. Or, most commonly from the alternator positive terminal being struck with a wrench at oil change time, and the main fuse being blown.

 

[quote author=RCW link=board=13;threadid=23926;start=0#msg226114 date=1071795119]
The code can be generated by a faulty battery temperature sensor, a bad PCM, or a bum alternator. Or, most commonly from the alternator positive terminal being struck with a wrench at oil change time, and the main fuse being blown.
[/quote]

I have been running with the battery temp sensor removed for the last year and a half. Since I put the Optima's in the truck. At first I was running with only the right side battery so the sensor was useless. It sets no code removed and lowers the charge rate a half volt or so. Running the road most of the time that is a good thing.

 

Suggest that you measure the battery voltage with the engine off. Then measure it again with the engine running. Also check the voltage coming out of the alternator. While you are at it also measure the voltage going into the alternator. Not sure on your particular model so have to talk generaly. If the voltage going into the alternator is more than about 9 volts then the output should be around 14 volts. If no output with at least 9 volts going in then it could be a bad alternator. In which case I would not replace it, but just get it repaired/rebuilt.
There are other things to check but this is a start. Let us know what you find.

 

hit the alternator with the oil filter wrench? who does that (me last weekend, lol)

that kinda sounds just like what happened with mine. i was only able to find the fuse at a dealer, cost me $7.40

 

I have checked the alternator and the fuse they both have checked to be OK. Perhapes it might be the voltage regulator in the PCM??? If so is there a way to bypass it?


Is there a manual or program on on performance upgrades.
(How to turn injection pump up ect...)

 

I will give you the true altinator test. Remove the plug or wires from the small terminals. There should be two small terminals on the altinernator. Do not disturb the heavy charge terminal. Hook one to ground, the other to 12v from the battery with it running. The alternator should go to full output. If it does not the alterantor is bad, if it does the problems is in the system. You might try disconnecting the temp sensor as I guess it could be shorted and it will charge without it.

Have you checked your batteries? Shot batteries could also do this. Easy way is to try a good battery in it temporarly with the other one disconnected.

If the regulator is in fact bad, it can be wired around, with an older solid state regulator controlling the alternator, but do not know what the code situation would be.

 

Where is the temp. sensor located at? (battery of water?)
Also, does it matter which terminal is connected to the ground ?

 

Temp sensor is mounted on the bottom of the drivers side battery tray and has about a six inch wire lead with the pulg on the end. Feel around for it under the battery tray and follow the lead to the plug which can be unplugged.

The two terminels on the altinator go through the brushes to a coil on the rotational portion of the alternator so it does not matter which is which. When the electromagnet is energized, the alternator starts putting out AC power at around 400 cycles, which is converted to DC by the diode bank.

 

Does your tachometer on the dash work? The PCM needs to see an engine speed signal in order to energize the ASD relay and turn on the alternator. If not, check the engine speed sensor and its wiring at the front of the engine.