bumpytruck

My wait to start light does not come on. I do not hear the grid heater cycle as well. I replaced the "relays" on the drivers side wheel well. I still have no grid heaters. The light come on momentarily as I have the key in the crank position.I went to my local parts house and when I ask for a grid heater relay, they want to sell me a little square relay, and I cannot find where it is on my truck.My truck is a 91.5.Its intercooled. Any help would be great. Thanks

taterfarm

here is the link from the sticky to repair the grid heater relays, there is no little square relays for themhttp://dens-site.net/Dodge_CTD/Grid_Heater_Relays/

There are two little signal wires that trigger each of the heater relays, you can check for power on one of these small wires to tell the relays to turn on, if there isnt any power there then there might be a signal problem, also check the larger diameter cables to see if they have battery power .

I think the heaters run from the air temperature sensor in the intake but am not certain on how that works, someone else can clear that up for you.

j_martin

There are 2 grid heater relays, side by side, mounted on the driver's side inside fender. They are 100-150 amp solenoids in actual fact.

It is highly unlikely that the relays themselves are bad. The PCM both drives the relays, and the light. It does it if the air temp is below about 50° in the intake manifold. There's also a protocol followed. It'll run the relays for one cycle before cranking, and then cycle them on and off til the engine temperature gets to a certain point after it starts. The lights don't light after the engine is running, but the grid heaters run on and off.]

Most likely fault will be the air temp sensor in the manifold, or the harness wiring to that sensor.

This is one of those places where a factory service manual is priceless.

bumpytruck

I did replace both of the relays on the fender. I was suspect that they were not the problem but I didnt know what else to try. After doing searches on here,I will add that the speedo does not work either,that seems to be tied into this,from what I have read.I will check the fuseible link,but were is it exactly?

taterfarm

the small blue wire at the relay on mine is the + signal for the relay, check that for power when the key is on. The link from the repair page say that it should preheat for 10 seconds if the intake is less than 59*F, so you dont have much time to check for a signal before it shuts off and you need to cycle the key again.


The two fuseable links for the heaters on my truck are right at the battery post, coming out of the large wrap of wires.

many people just add a push button switch in the cab to signal the relays to run when they want them.

how does the air temp sensor look in the intake manifold? those are very small wires and are easily damaged, the wire lead is short so they could have been pulled out. I think the sensor closer to the intake pipe must be the one for the heaters, the other sensor goes to the ksb.

TIMMY22

Also, check the thin wire opposite the blue. It's the ground for the solenoid. without ground the solenoid will not close.

j_martin

A bit oversimplified.

Power is supplied by the ignition system, key on.
The ground, operating the relays, is supplied by the PCM.

You can temporarily (as in seconds) ground the relays to test them and the heaters. Whatever you do, don't permanently wire the PCM operated terminal to ground.

bumpytruck

Thanks again guys!Problem was a broken fuseible link wire.The grid heaters and speedometer all work perfect again..

purecountry49

What size fusible link wire and length did you use to replace the original? And, where did you get it?

Thanks Up Front!!

I think mine need replacing because I can see them getting really hot and smoking just a little during the cold weather starting season!!

peckens

you can use an inline spade fuse they are about 2-3 bucks at any auto store or u can use a fuse block and get rid of many fuse links

TIMMY22

I did it w/ a momentary switch on a buddys truck no problem...Computer was disconnected or hacked in one way or another. Hooked up ground and ran the tickler wire to the momentary switch. Works great, they even wine when you hold the momentary in.

TIMMY22

And just why do they wine?

j_martin

You won't hurt the PCM if you ground that terminal with a switch. PCM output is an open collector circuit, which can be paralleled if you wish.