95Z28A4 wrote:
I am working on a grid heater for my wife's CRD. 65Corvair is doing the same for his CRD. I read a post (from Hexus if recall correctly) stating battery voltage dropped to 10 volts while using BOTH glow plugs and the Weeks intake heater simultaneously. Based on this, I decided a better solution may be to use both the glow plugs and the grid heater, but not at the same time.
The FSM states:
When the ignition key is turned to the ON position, the ECM sends a signal to the glow plug module to turn on, and cycle, the glow plugs for a predetermined amount of time, plus illuminate the glow plug light in the instrument panel.
MODULE-ENGINE CONTROL C2 (DIESEL) - 58 WAY
CAV_____Circuit__________Function
43_______D330 20WT/BR_____GLOW PLUG MODULE SIGNAL I think manual operation using a momentary contact pushbutton switch is the least expensive and most reliable mode of actuation for a grid heater.
Is it possible to tap into the glow plug module signal wire and use it to break the circuit from the pushbutton to the grid heater contactor? Possibly, a normally closed relay can be wired in series with the pushbutton. The glow plug module signal will trigger the normally closed relay coil. When the glow plug module receives the signal from the ECM, power from the pushbutton to the grid heater contactor will be interrupted by the relay dropping out the grid heater contactor.
If an indicator is desired, a 12 volt LED can be wired to the contactor. When the contactor coil receives 12 volts, the LED will illuminate indicating the grid heater is ON.
I am considering this Panasonic HY1Z-4.5V relay:
http://www.mouser.com/ProductDetail/Pan ... 252bp1I%3dAnd the White Rodger 120-901 for a grid heater contactor:
http://www.mouser.com/ProductDetail/Whi ... thOw%3D%3DThoughts anyone?
How long does the grid heater need to be on to get hot enough?
You could use a timing circuit that when turned on powers the grid heater for like 5 seconds. If necessary, you could reset the timer and power it for an additional 5 seconds and repeat as needed.
This could all be wired up to work with ignition key off.
You should power the circuit diectly from the battery. Therefore your relay should be a 12 volt relay with 50 amp contacts. A timing circuit may not be necessary at first but may be helpful down the road once you figure out the optimal on times.