OK guys, it is getting cold around here now and I need these heaters to work and I can't find the problem! the problem is with my 98.5. The wait to start light works properly and stays on until it's preset limit but the heaters never turn on. I have checked the solenoids and the connections and they are working fine. When I manually trigger the solenoids the heaters turn on and work fine. The IAT sensor appears to be working fine as it recognizes when to turn the heaters on. Am I missing something? A fuse or relay I don't know about? I just hope the PCM is not the cause of this problem.

Any thoughts?........I'm stuck......

 

Ok... Let track this one down..

1. Do you got voltage to the solnoid? With the key off one side should be hot and the other side should be dead.

2. With the key on... Do you have trigger voltage? (The smaller wires).

Just a gut feeling is the solnoids have pitted contacts and are not making good connection any longer internally.

Or...

The singal from the ECU is sending a weak signal or you have a bad ground...

Just my 2 cents for the morning...

 

Thanks for your .02

To recap,

When the solenoids are triggered manually, they work fine and the grid heaters work. The connections including the grounds were checked and work fine. With the key on and a cold engine, I have NO voltage on the solenoid trigger wires.

 

I think my truck may be doing the same thing. Where can I find these solenoids and relays so that I can test them?? I'm tired of sitting in the driveway cranking and cranking the dern truck till if finally fires. Also I can hear my grid heaters come on and off and the Wait to start light is working fine also...

 

If you can hear your grid heaters cycle on and off when the truck is running, they are working. I'm not sure what relays you are talking about but if you are wanting to test the heater solenoids, just put (+) power to the trigger terminals on the solenoids (one is ground the other is switched (+) power) and check the terminals at the heaters for continuity.

 

Anybody else have any ideas?

 

Check fuses, and check relay in PD box(swap with another relay to test). Check your IAT sensor for proper resistance, and check the plug in connector to it, for a bad connection, or wire from plug not pushed into connector fully.

 

What relay in the PCD?