Voltage woes Again

[J DeMaio]

Okay boys:



This morning after I fired the rig up and let her idle fro a few minutes after a cold night (It was plugged in). I turned on the lights and noticed the radio quit working, after a couple of moments I looked at the voltage regulator and it was reading 0. It stayed this way for about 9 miles and then kicked up to 12-14 like normal. Now, It's done this for sometime and it's beginning to be a pain. The gauge will either stay real low or fluctuate like a windshield wiper. I went to Autozone (Voltage guage reading normal) and they said the voltage regulator, alternator, and battery were fine. Something has got to be wrong. I was thinking of the voltage regulator myself but they are expensive since they're part of the computer and I still can't seem to find where it is at. I need some suggestions.



Thanks,



John

 

[Philip]

Autozone

If your store is like the one we have local here. They would barely know what a charging system is, let alone know how to troubleshoot it right.



Have you checked to see if your truck has stored any trouble codes?



How old is this battery? All charging systems are controlled by the resistance the battery builds up when it is reaching full charge. Some batterys getting close to failing will have a high resistance in them. When a battery is in this condition before death. It will make a charging system do all sorts of strange things. Things you are seeing right now are some of the syptoms.

When AZ checked the battery how long did he leave the "small" load tester they use on the battery? If he left it on for only 20 to 30 seconds. It is not long enought for our batterys. That little tester they use is made for small car batterys. To do a proper load test you are supposed to load the battery at three times the amp hour rating for 30 seconds. The tester that AZ uses might go to a 200 amp load. Our batterys need around 1000 amps for that long. So the test they did on yours would have been bogus.



So the first thing. Does the truck have any stored codes. To see that. Turn the key off and on three times. leave it on the third time. Watch the check engine light. It sould start flashing. Count the flashes. Any delays between flashes means to start counting on another number. The flashes will be 1 second apart. If you see a 2 or 3 second delay. You are on another number then.



After you confirm no codes then the fun parts starts. This isn't an easy circuit to troubleshoot long distance.

 

[Paychk]

Check your ignition switch and make sure it fully returns to the run position. Sometimes it sticks half between run/start and you won't get anything. If this is OK, go to the next simple step.



Wiggle the crank sensor up at the harmonic balancer and see if if corrects the problem. The engines that come with the computer, have the alternator controlled by it and won't energize the charge circuit until it knows the engine is rotating.



Start simple then work to the complex.



PS Simple things such as fuses? BTW the computer is behind the battery and the main connector has been know to corrode ? due to the close position to the battery/acid vapors?

 

[J DeMaio]

Okay guys, I'll start here. The ignition switch is fine. I did the test by switching the key off and on three times, it did not work. After the third time when the check engine light went out, it never came back on. So now what should I check?



Thanks,



John

 

[J DeMaio]

BTW, the battery is a 1000 CCA and is about 2 years old. This problem usually only happens on startup at very cold temps but does sometimes do it while going down the road a few miles later That test autozone did was supposed to test the whole system, he left it on for a couple of minutes. The diode in the battery was supposedly good, the alternator was fine, and the computer was good he said, voltage was at about 14 volts. I don't think his diagnostic tool was much count. He didn't test the battery load or anything like that. I'll check that crank sensor, does this thing go bad?



Thanks again,



John

 

[RBergman]

could the heater(i think it is called the grid heater)

cause this? if it where not cycling? i have never lost

my raido but have lost the display screen. and when

cycles off it comes back... just an idea

 

[paccool]

I'm with RBergman



If it happened on a cold morning, almost has to be related to the intake air heaters. One of the relays might be sticking shut. I'd pull the power leads from the relays and try it to see what the volt meter does. That might isolate the problem to one area and make it easier to find.

 

[J DeMaio]

My wait to start light never comes on again after the truck is started. Why would it come on again later after the truck is fully warmed? I don't know what to do.



Thanks,



John

 

[RGT]

The wiat to start light coming back on would have me looking for a bad connection in that circuit as it should only come on initially when it sees the key turn on... . it could also come on if the voltage went real low and then came up again, so that it thinks it saw the ignition go off and on... good luck

 

[Philip]

The grid heaters can cycle at anytime the temps is below 40. After the first turn of the key. After the wait to start ligh has gone off. The heaters will still cycle for a while. They are controlled by the intake air sensor and the coolent temp sensor. I am not sure of the temp where the computer will stop running the grid heaters at.



The gages moving like a windshield wiper is the grind hearters cycling.



The droping to 0 on the gages sounds like ground problems with the gage panel.

 

[PPeters]

I believe the temp cut off point for the grid heaters is 60F. Above that, they don't cycle.



Pat

 

[Philip]

The 60 degree is for outside air.



What is the coolant temp when it stops cycling the grid heaters on a cold day? Or is it controlled by a timer in the computer?

 

[PPeters]

Sorry Phillip, I was reading the shop manual last night and thought that was the number you were looking for



Have to check it again tonight.



Pat

 

[PPeters]

I'll apologize up front for the length of this post, but in the interest of being complete this may help. Get this from the '92 Service Manual, ch 14-109



The air intake heaters are energized by the engine controller through the air intake heater relays. Intake manifold air temp determines when the heaters energize. They may be energized before cranking and after cranking, or both. They are not during cranking. They are further divided by a pre-heat and post heat cycle.



The engine controller powers up when the ignition key is turned to the ON position. If intake manifold air temp is 15C(59F) or below, the heaters are energized and the WTS light is lit. The heaters cycle for a specific amount of time in preheat cycle, according to manifold temp... 59f and above: 0 sec, 18f to 59f: 10 sec, 1f to 16f: 15 sec, -15f to 0f: 17. 5 sec, below -15f: 20 sec. Once cycled, WTS lamp goes out.



After engine starts, the post heat cycle will begin if manifold air temp was 59f or below when the ignition was turned on. Depending on intake manifold temp, either both heaters are energized or they are cycled on and off (when one is on, the other is not). The time they are energized follows the above schedule.



Concerning the WTS light coming on while operating:



pg 14-111 in manual states the following...



The WTS lamp is turned on and off by the engine controller based on the charge air temperature sensor input. The light is turned on when ignition is first activated and remains on for 2 sec as a bulb test. If engine controller reads manifold temp below 59f the WTS lamp is turned on for the preheat cycle. The WTS light will flash on and off if the charge air temperature sensor input to the engine controller is below minimum or above maximum value. The engine controller stores a fault message when these conditions occur.



Hope this is helpful



Pat

 

[Philip]

The WTS light will flash on and off if the charge air temperature sensor input to the engine controller is below minimum or above maximum value. The engine controller stores a fault message when these conditions occur.

jdurham had his sensor go bad a long time ago. it didn't store any codes. the heaters just didn't work. His Wait to Start light would just come on for a few seconds like the engine was warm. Then turn off the heaters. His was below value.

Boy that was a lot of typing. PPeters LOL

 

[jdurham]

Philip is right, mine never flashed, until I unplugged it to check it, but it never worked either. One new sensor later, and it makes the truck actually run when it's cold, and it doesn't take three or four attampts to start it.

 

[J DeMaio]

Okay Guys:



The grid heaters seem to work fine. The WTS light was on for ~10 seconds this morning and it was probably 15-20*. So, The two main questions I have now are: Where is the crank sensor located? and How come when I turned the key three times to retrieve the codes nothing happened like it should have?



Thanks, this info is very helpful.



John

 

[Philip]

The crank position sensor is located in the front of the engine right above the harmonic balancer.

On the checking for trouble codes. You need to turn the key off and on three times in about 5 seconds. If you did it to slow then it wouldn't have noticed you were wanting trouble codes. If you had the batterys unhooked it would clear the codes also. This old computer on our trucks do not store codes if the battery is unhooked or goes dead. As far as I know they do not.

 

[PPeters]

Phillip, hope you didn't take my post wrong, just wanted to provide complete info as presented in manual. In no way was I questioning your experience



Pat

 

[Philip]

PPeters

You did not offend me in any manor.



The manual is a starting place for checking. But That is all it is. There are so many things that can go wrong on a auto/truck that the manual just covers the basic's.



My posts are long most of the time. I try to explain the operation as much as possible when I think it is needed also.



I liked it when you threw the section from the manual in the thread. I might have answered a couple of questions someone might have had that doesn't have a manual.



If I had a scanner and the hard drive space. I would have the whole manual on this computer. LOL