rvaughn801

From the starter relay connector (starter relay removed), I have 12V when the key is in START on the yellow wire, from the ignition switch. I also have continuity from the starter relay connector to the starter solenoid terminal (brown wire). So the starter relay ($12) is suspect, and I will replace that next. It looks to be original. and I haven't replaced it in the last 10 years.

Thanks for the replies, very helpful.I found several pics of a starter relay, but haven't found one on the truck. Could I get a hint where this is located?On the right side of the wiring diagram is a rectangle marked "31". Is this a fuse or fusible link? Any idea where this is located?Thanks again.

0V at solenoid terminal when in START position. Do you mind giving me some pointers on how this works? Is this likely an electrical problem with the ignition switch? I see a rod moving when I turn the key. All the accessories work when the switch is ON, and the accessories go off when the key is turned to START.Looking online at the part picture, I think I replaced this part several years ago

So far I have tried the following:1) Charge and test the battery at NAPA -- battery tests out "Good"2) Test starter at NAPA -- spins easily, sounds good3) Removed starter solenoid cover -- oil on contacts, contacts and plunger are pitted. Cleaned and sanded contacts4) Clean and tighten battery terminals5) Clean main engine groundThe only idea I have left is to remove the positive cable and ohm it out to see if it has a broken connection.The starter contacts do not look like new, and are probably 8 years old. Is it possible the starter will run for NAPA but won't on the truck because of contacts?Thanks in advance for your help.

Dumping the freon would not be a big deal, as the A/C hasn't worked in 10 years. It is still and R12 system. I will prod the valve with a screwdriver and see if anything comes out.This truck originally came (in 1989) without A/C, and A/C was added by a dealer in 1992. Does that make a difference? You can see in the pics the sloppy cuts in the dash for A/C vents. It was a Canadian truck, with metric speedometer and no cruise control.This is the 2nd heater core that has gone bad. A shop replaced the first one for me, for $90 labor (I supplied the part). They didn't mention evacuating the freon.The part I bought has a lifetime warranty, so I wanted to do it myself. That, and the face that this core only lasted 5 years, so I felt like I need to know how to do it (if only Cummins made the rest of the truck!)I think I've already asked, but any chance I could cut an access hole and patch with rivets? I would like to get this back on the road. I apologize for trying to take short cuts, but this is a busy time of year. Thanks again for all the help.

Thanks for the help. I got a little farther last night, and will get started again once I get some presents wrapped Fortunately I have another car to drive to work tomorrow. The heater box is still not free, so I may have missed a fastener on the engine side. Once I can pull the box away from the firewall, can I get the core through the opening under the center of the dash, or does the top of the box need to come up and off? Again, thank you Michael.

I took some photos. Please let me know what you think. Thanks!

My heater smells really bad, and I have taken it apart far enough to reach inside to the bottom of the plastic heater box and feel antifreeze. So it needs to come out.The issue I have is how to get to it. There is small panel that comes off easily so I can see part of the core. I can also see a vacuum actuate flap that closes off air flow to the core.At this point, is the best plan of action to remove major pieces of plastic and/or dash to get at this? Or is that needed? I haven't found a step by step removal how-to for the 1st Gen D250. But how-tos for other cars talk about removing a small rectangle of heater core box for access, then riveting a cover over the hole. Has anyone done this?Thanks in advance for your help.