bisongus

After replacing batteries and starter truck still has a long crank to start and its not even cold out. If plugged in starts very fast so think it's the grid heater. Removed air horn above grid heater and cleaned all connection points. Cycle key and grid is hot. Replace everything. Removed and cleaned relays, film of oil from vent hose I guess. Clean all connections. Reconnect wires. Air inlet temperature sensor working fine as light on for few seconds if engine is warm. Relays cycle on for about 15 seconds otherwise. Test system as per Dodgeram.org Manifold Heater Problems. Instructions were for '01 - '02 engines but the wire colors are the same. With the relay power feed disconnected I read 4 volts on the orange and yellow wires supplying the relays. Connect everything and the voltage at the grid heater is 11 volts during the cycle. Intake above the grid heater is slightly warm to touch. Should it be hot? Could the relays be faulty? Did I miss anything?

patdaly

What year truck are we talking about?

bisongus

'99 3500 Quad cab ,long box ,4x4 , 6 speed manual. AFE Stage 2 air filter. Fuel pump in the tank.

patdaly

Ok, at some point, perhaps 01? they changed the GH solenoids from a ground to engage to a power to engage.

Your 99 is just like my 97. Essentially you have the two solenoids with a large supply wire from the battery to on of the large studs, then another large wire from the other stud to the heater. Next you have the small studs, one side has a constant 12 volts applied whenever the ignition is on and the other is hooked to the PCM. When operation is called for, the PCM applies ground to one or both small studs and the solenoid engages.

Testing it is relatively easy, just take off the ground side of the small terminals and touch from there to a ground. You will hear the solenoid click if it is good.

patdaly

Oh yea, one other thing, the supply from the battery to the input of the large terminal on the solenoid is a fusible link, and has been known to corrode and not provide enough power. You might want to closely inspect it for signs of corrosion under the sheathing.

bisongus

Ok I will test the relays. I do get power at the grid heater. Will check out the fusible links. Looked ok when I cleaned connections but will look careful at them

KATOOM

Here's a link which may help. Ram Diesel Manifold Heater Problems

toesmack

Had a pretty hard time getting my 01 to start last week in Wyoming, it was below 0 deg.F. Got it home and found suspect connections due to corrosion. Cleaned it all up and get good contact and heat from one side of the grid heater. Including cycling after startup, just like the last 16 years. The other side of the grid heater is cold, and second solenoid is not firing. Does this truck fire both at the same time, or just one determined by air temp?

Since new this truck has always started instantly after heater cycle, even in temps down to -40. This is the first time it ever had a slow morning.

KATOOM

Read that link I provided as it should help you understand what the grids do. But in answering your question, both elements heat up during the initial WTS period. Then after the engine is running they alternate. You can even pull the intake horn off and rebolt the grid element back down and start the truck. (Obviously making sure nothing gets accidentally sucked in) You can see how the grids glow.....

toesmack

Yep read the link, and thanks for the info! Did not know they did a switch hit act during warm up. Could not tell from the schematic if they both fired at the same time. Will do a bit more troubleshooting when we get cold here again.

patdaly

You could always go full retard like I did before I fully understood how they worked.

https://www.dieseltruckresource.com/...orking-189976/

KATOOM

I remember that thread.....

toesmack

Found a relay that was firing but not always passing current to the grid. Replaced the relays (Amazon) and works great now. Just needed some cold weather for the troubleshoot.

torquefan

Good find! It's a pretty common failure, I've replaced several. To test them, I'll usually go out on a chilly day, and clamp an amp clamp around the two feed cables on the preheater. Turn the key on and you should see about 200 amps being drawn by the two elements together.