Engine/Transmission (1994 - 1998) Voltmeter surging

[firemanmarc]

Another post of volt meter surging. . I have narrowed it down the shutoff solenoid circuit. When the feed wire is unhooked from the battery, the surging stops. I do not want to just buy new parts. I would like to try and diagnose this issue. . I would appreciate any help. Thank you, Marc

 

[K5IP]

Are you sure you are unhooking the right wire? The fuell shutdown solenoid draws a small ammount of current (unless it is shorted). Even if shorted, It is hard to envision why a short would make the voltmeter fluctuate.

Fluctuations are usually caused by very heavy loads like the grid heaters which are indeed switched on and off. (90A each)

I like your approach, figure it out, don't just change things.

Keep us posted,

Rog

 

[GROBBINS]

Mark, I am having the same issue. When was the last time that your alternator was replaced. I believe that mine is still original. My meter fluctuates intermittenly. In the morning it seems fine, once it warms up, and I have my fan or lights on that is when it is the worst. Drops from 14-15v to 12v. I also just got the truck back from a shop that replaced my melted intake relays, told them about the voltage drop and they told me that was another problem not from them, but it didn't do it before they were replaced. It seems as if the grid heaters are cycling when they shouldn't be. I also want to get down to the bottom of this. Otherwise I am looking at replacing a third set of relays soon. Keep me posted Gabriel

 

[JJW_ND]

Grid heaters....

There might be a better way, but a cheap diagnostics is the remove the two heavy cables that connect the grid heater terminals on the intake (very top front of engine). Make sure you tape them off or protect them from shorting out on any metal. If your fluctuation quits, it is the grid heater solidnoids. I think it is pretty common for one of the two solinoids to fail causing it to bouce on and off. I got a 150K out of the factory solinoids. Have about 140K on the replacements.



I was fighting this in the middle of the winter and found I could get by with one grid down to -10. Above 30 degrees ... . no grids needed.



jjw

ND

 

[firemanmarc]

Well so far so good with the relay feed wires unhooked. Looks like I will be replacing the relays with the Stancor ones mentioned in earlier posts. My alternator is about a year old. . I really think it is my heater relays as they are original with 290k on them. . Marc

 

[Vaughn MacKenzie]

Another thing that'll cause fluctuations is a poor connection of the heavy lead from the alternator to the battery cable. Make sure this is good and clean & put some corrosion prevention gook on it.

Vaughn