during the summer, i had some probs with what i think is the relay for the wait to start deal. im not really sure what i have or what it is, other than its not glow plugs ; )

so anyway, under the hood, mounted on the wheel well (drivers side) is a device that has two wires on one side and two on the other. kinda like a connection block. well one of the wires became hot enough one day to melt the rubber boot that was proctecting the wire from the weather. so, like a lazy bumm, i just disconnected it rather than actually finding a solving the problem.

now its getting cold here and when the wait to start light comes on i no longer hear any humming or click or the hood. so i remember that i unhooked that wire, and i hooked it back up, but still i cant hear anything working under the hood during the what to start period.

oh yah, im new to the board! heres to my first post, hope you had a happy thanksgiving, i know i did!


edit:guess i could have posted the year model. its 91 250 12 vavle CTD, with over 230,000 miles. non intercooled and it is an automatic tranny.

 

Welcome to the DTR!!! 8)

As for the melting of the boot, I assume you are talking about the grid relay. Basically there are 2 relays. They each have 2 small gauge wires with 90° elbow connections and then 4 heavy gauge wires, 2 to the battery and 2 to the heater. If the large wires melted, I would think that the heater grid may have burned out or shorted, or the wires rubbed through somewhere. Maybe try to explain it some more if you can and we can take another stab at it.

FWIW grid heater failures are not very common.

J-eh

 

okay, heres another stab. your right on about the relays. the two heavy ones going to battery are fine. its one of the heavier wires on the other side of the relay that got hot and melted the boot. im guessing these two wires are just running to another relay which is what i see mounted on the intake. again with two heavy wires on one and then the other two same diameter on the other side. this relay did not get hot enough to melt any of the rubber boots.

oh, and heres one for the "im an idiot board". when i hooked the wires back up, i managed to hook them up wrong. two wires, the one that got too hot and the other one, both running to what appears to be another relay. anyway, i switched them back and now i have the click sound back.

but last winter and all winters before i could hear them humm before they clicked off. now they dont humm at all. still it wasnt that cold (like 45+) so it did start without all that rattle that i expect to hear soon in colder weather.

after reading your post again, this system does consist of two grid relays and a seperate heater grid. where is the heater grid located?

 

Well I think we are talking the same thing.. Thats good.

The heater grid is located just under the intake elbow coming from the turbo. There is a small block spacer about 1" tall under that aluminum horn piece (the one that says Cummins Turbo Diesel on it). You will see the heavier gauge wires come in on one side on the back and then a ground wire going to the block right near it. I think you were describing it as another relay on the block, thats the heater grid. I would still check the wires to see if they may have rubbed through.

I am not certain, but the wires to the battery should be checked for continuity too to make sure you have power to the relays. It sounds like one of the relays is stuck and overheated. This may have burned out the grid heater too, not sure.. :-

 

Check that the small right angle wire pushon connectors are in the terminals on the relays. Mine comes of now and then, it will also set a code.

 

okay, i just went under hood to see if all this makes sense. and amazingly it does! : )

so i have one relay and a heater grid.

are the heavy gauge wires supposed to be hot or just one of them?

 

Well tracing the wires from the battery, they should be hot full time to one side of the relay. The other side should be off, except when the relay is activated, right?

So, if you have a test lite, see if you have the hot side powered. Then see if the heater side goes hot with the click of the relay.

 

if i wanted to test the heater grid when its above 50f outside, could i just bypass relay?

i'm thinking its just the relay. or let me rephrase that. im HOPEING its just the relay. hehe

 

Good Question..... ???

I don't think just unplugging the IAT sensor would work..

Sheezz.. Above 50°F eh, must be nice.. :

 

well isaid that, because overnight it stays plugged up. now its 30f something outside. but i have to be able to drive it, so i cant leave it where its at and run test on it. not at this temp. at 45+ i would leave it unplugged and use volt meter to see whats going on.

"I don't think just unplugging the IAT sensor would work.."

i meant hot wiring the heater grid to see if would activate. in other words, im planning on taking those heavy guage wires and touchin them together on the respectable sides to see if the heater grid humms like it used to.

 

update:after rewiring the relay properly and getting caugt in the cold without the truck plugged up, the heater grid works.

so as said before, there must be a wire rubbing a ground somewhere.

i need a wiring diagram. is there one posted on the web for a 91w250 heavy duty CTD?

only manual i have is a haynes or clymers, and they decided NOT to include the CTD...