In an earlier post, I had a problem with the cold start heater grid on my 1992 D350. I replaced the ignition key and wiring in the steering column thinking it may be a bad connection, but no such luck. I have heard of guys wiring in a switch to manually control the heater grid. Does anybody know how to do this? I am at a loss as to where to begin. Any any help will be appreciated!!
-Jackson

 

since the relays that control the heater grid take a low current input to activate them I can see just useing a 12-14 gage wire from a switched source with a switch in the middle to turn it on and off.

I say useing a switched source so you have to have the ignition to on for it to fire up so you dont kill your battery.

I remember someone posting a wireing diagram, might have been you. This would show you which wires to cut into.

 

With the ignition in teh "on" position, i have issolated that the yel/blk and org/blk running from the powertrain control module to the heated intake air system relay 1 (yel/blk) and relay 2 (org/blk) act as a ground wire to complete the circuit and this engages the grid system. I know that i can wire a switch into the ground wires to make the stsyem work, but the system does not shut off automatically as it should. I was wondering if teh powertrain control module could be failing and not completing circuit properly. Is there anything i can fix or replace in there? As of now, i can make the system work but i want to have the system working properly and automatically if i can.

[IMG]local://upfiles/25952/4CA6283568A2460598E27C11C1629BB3.jpg[/IMG]

 

from what your saying it does sound like the module is going bad