Hi guys I'm new to this forum and hope somebody can help me.The other day I noticed that my battery guage was drawn way down when I was driving so I shut the truck off and started it up again to watch the manifold preheat go thru its cycle wich is normal but usually only happens if the truck is cold,Anyway the next day when I started it the guage is staying down like the pre heat is stuck on? What exactly controls this and how do I fix it.Just to make things more complicated the truck has been sitting in a airport parking lot for the last week and I hope to fly back tommorrow with the right part to fix it and then drive two hours to a job.Thanks in advance.The Truck is a 91 3/4 4x4 thanks Grant

 

Check your batteries when they start to go they drain the altenator. Thats what happened on my 01. You can sometimes smell them. welcome to the site you'll like it here.

 

Sorry but I just put in a brand new battery about a month ago and I am pretty sure the grid heater is stuck on.Sombody out must have a factory manual or some idea what controls these heaters?

 

[quote author=Grant.G link=board=13;threadid=6824;start=0#64636 date=1036904242]
Sorry but I just put in a brand new battery about a month ago and I am pretty sure the grid heater is stuck on.Sombody out must have a factory manual or some idea what controls these heaters?
[/quote]

Sorry Grant, not for a 91. In the mean time, how 'bout pulling the heater relay or fuse?

 

there are tow sensors on top of the intake manifold behind the elbow. One controls the KSB, and the other the heating grids, via the &quot;computer&quot;, which if you have a manual transmission before '92 doesn't seem to do much more than control the heating grids. The two grids are powered via their own (two) relays which are the two big relays on the driver's fender. The &quot;computer&quot; is tucked up inside the fender behind the battery. So -- possibilities are a bad air temp sensor, a stuck relay, and a bad computer. The sensor is supposed to have variable resistance according to temperature -- haven't had to test one yet. The computer would have to be diagnosed by process of elimination I think. It is possible that the wire from the sensor to the computer is not making a good connection, but even if that were the case, or if the senser were bad, the grids should be turned off after a while -- so I am leaning to stuck relay and wishing you luck.<br><br>

 

A quick note on the 91's. Depending if you are intercooled or not will also determine the position of the intake air sensor. ON the non intercooled trucks the sensor is a 2 pin plug just under where the intake elbow connects to the intake manifold. If you unplug it and run the unit the WTS lite will flash at you to say something is wrong.<br><br>Also the computer for the WTS system is actually in the dash and not behind the battery in the fender for the non intercooled units. The CUMMINS consol has some of the brains in it for the grid hears I believe.<br><br>I would pull the two wires off of the battery terminal that run to the grid heaters.. Depending on the repairs to the positive cable, they may still be a permanent fixture. If so then disconnecting the main leads OUT of the relays will help.<br><br>Also on the early 91's the voltage regulator is an external unit mounted on the firewall just above cylinder #6. he regulator is about $10 at any parts store. If this unit is TU then you will also have the large drain on the battery.<br><br>One more thing. I had a similar problem with my 89, the problem (after much troubleshooting and swearing) was the ground cable to the block was corroded from the inside out. If I wiggled the cable just right, I would get full charge, close the hood and the lites go out...What a fiasco...<br><br>Anyway Good Luck..<br><br>J-eh<br><br>