Engine/Transmission (1994 - 1998) grid heater not working

[Keith1]

1st wait for heater light to go out

2nd start truck or should i say try to start it

3rd truck starts but no cycle off heater was 16 here this morning



replaced the air temp sensor cleaned battery post and other grounds but still no cycling off grid heater any help appreciated.

 

[shendren]

try tightening the nuts on the grid heater solenoids mounted on the driver's fender well. they have little rubber caps on them. they are probably loose.

 

[Keith1]

cleaned and tightened nuts and still only get the first 10 seconds then start and no cycle

 

[shendren]

is the pcm throwing any codes. i believe the pcm controls the grid heater cycle... ... ... .

 

[DMC]

Try swapping fuel shut off relay with the grid heater relay. They are up on the firewall to the right of the brake booster and brake reservoir.

I'm sure you know that when the grid heaters cycle they will cause your volt meter to swing significantly when the temps are very cold. this will be an immediate indication that it is working properly when you do get it working.



I hope this helps



Don

 

[shendren]

on my 96 they are to starboard of the brake booster. the grid heater relay is the starboard of the 2 relays.

 

[Joe G.]

The relay on the firewall next to the fuel solenoid relay is the fuel heater relay, not the intake manifold heater relay. The two relays below the passenger side battery are the intake manifold relays.



According to my '95 service manual pg 8W-30-41 the start/run voltage is applied to the light green/black wires to the relays. The circuit is made by a yellow/black wire from relay 1 to the PCM on pin 16 and by an orange/black wire from relay 2 to the PCM on pin 15.



You need a volt meter to test to see if the relays are being energised. Since you are getting no heat at all from either of the grids I would remove the wires from the relays and clean them before doing anything else. You live in a salty part of the country and corrosion may be your problem.



EDIT: Should have said DRIVER'S side battery.

 

[Joe G.]

I've read a little more in my service manual about the intake manifold heater circuit.



One way you can test it is to remove the orange/black and yellow/black wires from the relays. Turn the key on. Connect test leads from a ground to the terminals you removed the wires from. The heater grid should come on. If it does then you may have a problem with your PCM. If it does not, than make sure all connections are clean and tight and try again. If it still does not work, then remove the wires from the heater grid terminals and use a ohm meter to check the heater grids. You should get a reading on your meter of 0 ohms between the terminals on the heater grid and ground if the grids are ok. If the grids are ok then you may have bad relays. I would be surprised if both of them had failed.

 

[DMC]

Joe you are correct. Its been a while since I had to mess with the fuel heater relay and shut off relay. I'm sorry for the misinformation.



Thanks For taking the time to straiten me out.



Don

 

[ramman]

check The IAT

You may want to chech the intake air temp sensor,I think the resistance readings per temperature are in the service manual,I don't have one handy. It is the sensor screwed in the intake plate.

 

[Joe G.]

I forgot about that thing. Here is the resistance chart from my manul. It is located just behind the air horn on the top of the intake manifold. Remove the two wire connector and test with an ohm meter. .

 

[Keith1]

when i turn the key on they do come on for the 10 seconds or so its after it starts that they do not cycle,no codes,just no cycle starting to look like a bad pcm.

 

[Joe G.]

The temp sensor could also be the problem so you should check it before spending any money.

 

[Keith1]

checked yesterday and even put in new one but still got the same results,thanks for all the help.

 

[Dennis Garrett]

On my 97, on the driver's fender well, I have a common bracket with two grid relays on it. You should have cables from the battery, going to both relays, and cables out, one to each heater grid. While it's cycling, touch a 12v test meter to each cable, or grid, and see if both are getting current FROM the relays. If one of the relays quits, the volt meter will still cycle, but it will start hard.

 

[DBranzovsky]

I have a heater grid problem. I think that my grid is bad since the relays came on and wire have no corrision. Anybody have a idea what the grid heater intake combo will cost

 

[DMC]

Do you mean the grid heater is cycling in temps above 59*.



Or do you mean that you get the wait to start indication?



If they are cycling in this warm weather, there will be a noticeable drop in voltage. That will be evident on the voltmeter.



Give us some more info.



Good Luck



Don

 

[shendren]

check the bolts on the solenoid on the fender well. they are ususally loose. there's probably nothing wrong with your grid.

 

[BV]

If your getting the first 10 second Pre start heat cycle then the grid, wiring, solenoids and fusible links are all good. The only thing it could be is one of the sensors telling the PCM to not run the Post start heat cycle or the PCM its self.



DBranzovsky - Make sure you check that voltage is going threw the solenoids. I had one that would click but not close to allow the grid to have the volts. Also have seen the fusible links melt. They are located between the drivers side battery and the solenoids.

According to the parts look up from Dave Smith Motors:

INTAKE heater, Ram 2500,3500 94-00 $130. 00 $110. 50

Fuel system - Fuel supply - Diesel fuel supply - Intake heater



It might be less expensive through a Cummins dealer/distributor.

 

[shendren]

guarantee you it ain't the pcm.