Hmmmm. Paid about $90 for the Dodge ones a couple of years ago. If I'd have bought them last week I'd be choked right now. I guess time does heal all wounds.

 

Bill, do the relays look similar? Is it obvious which wires to go which terminal?
Thanks!
Dave

 

The starter relay will look somewhat like the one below. Two big studs are the supply from the battery and to the grids, they can be traded. The two small studs (one is hidden in the picture) are the trigger, connect the two small wires to these, they can be traded.

Now the exception to this is if you get a relay with a grounded body, it will only have one small stud. Find out which small wire is ground and connect this one to the screw that holds the relay down.

Better off asking for a relay with a non grounded case like this one
http://www.surpluscenter.com/item.as...tname=electric

 

Great! Thank you Sir!
Dave

 

Hello Everyone...New Here
I also seem to be having problems with my preheaters as well so I went out to the truck today and started testing. With the truck off and the keyswitch on, the heaters don't work. It seems that the relays are bad. The relays have power on the coil side, but are not closing to get power to the preheaters. We checked the ground side of the coil and found 94 ohms of resistance on each from the ground wire to the negative terminal on the battery. We checked and cleaned the three grounding sources on the drivers side body. When the truck is started, the relays will go in for approximately two to three seconds and then back out. This cycles several times. With the key switch on and the truck not running, if you unplug the power side of the relay and then plug it back in, the relay will chatter for a while. If the negative side of the relay is grounded to the negative side of the battery with a separate wire, both relays go in and hold, and the heaters work. Is this just a bad ground, or are both relays shot? If it is a bad ground, where are the relays grounded to? Does anybody know what's going on here? Thank you for any help

Tom

 

How cold is the engine?
The grids won't energize till the temp drops below 50F
To check the relays run a jumper from the battery + to the + triger side of the relay, should stay closed and the girds will heat if the relay is good.

One of the small wires is ground but somewhere along the line, not sure which year, the ground was provided by the pcm when the intake temp sensor called for heat. If this is the case one of the small wires will always be a hot positive with the key on.

Here's a '97 wiring diagram, yours might not have the same colored wires but will be similar

https://www.dieseltruckresource.com/...sort/1/cat/500

 

The temperature today was in the mid 40's. I will look in to your suggestions in the morning. Thank you very much for your fast reply.

Tom

 

I tried getting alternator parts from local NAPA store. They found the P/Ns, but couldn't get order info.

I ended up ordering from
Northwest Power Systems
Po Box 160, Thief River Falls, MN 56701
(218) 681-5282
800-570-5282

Alternator brush set, rectifier and 4 starter brushes was $60

edit
found 800 number

 

As long as we are on the subject of grid heaters. Is there any advantage to disconecting them for the summer? Maybe save on the batteries a little. If so whats the best way to disconect?

 

Just remove the small wires from both of the relays down and a little to the rear of the driver's side battery. They just slip over the posts, shouldn't take you more than 30 seconds with no tools involved.

 

I have had a problem with the Ford units overheating, because they are intended for intertmittent use only. 12V contactors from a RV store cost more, about $15.00 - $20.00 but are made for continuious duty, and are rated at 80 or 100 amps.
Bruce