Grid Heater Bypass

 

Installing this bypass will allow you to manually control if and for how long you want to run the grid heaters when the ECM is commanding the grid heaters on.  This will reduce the load on the alternator/charging system and in turn reduce the harmful AC voltage.  This bypass will also keep the fault codes P0380 Intake Air Heater Relay #1 Control Circuit and P0382 Intake Air Heater Relay #2 Control Circuit from being set.

 

  

 

Parts needed:

1.  2 micro relays, terminal 87 (5) normally open (NO) with suppressor                                                                                                                

2.  2 5 watt / 20 ohm resistor

3.  1 single pole single throw switch (spst)

4.  2 male bullet and 2 female bullet connectors

5.  2 ring terminals

7.  Rosin core solder

6.  10 female quick connect terminals

8.  Heat shrink

9.  ¼” protective wire cover

10. Electrical tape

 

11. Wire 18 AWG  4 different colors would be nice.

12. Optional    3 ATC fuse holders with 2 amp fuse

13. Something to mount the relays and resistors on.

14. 5 or more  6” zip ties

 

 

          Micro relay

                             

 

Putting it together

To mount the relays, resistors and fuses I used part of a used relay mount from a Volvo that I found.  It was cut and modified to fit the parts.  

 

 

I didn’t want to cut the wire harness at the fire wall to access the solenoid trigger wires, yellow/black and orange/black, that goes from the Engine Control Module (ECM) to the grid heater control solenoids.  I ran two wires to each solenoid connecting to the trigger wires with the male bullet connectors.  This sent the trigger signal back to the control relays at terminal 30 (3).  Two more wires were run from terminal 87 (5) of the control relay back to terminal 86 of the grid heater solenoids and connected the wires with the female bullet connectors.

                                    

 

 

 You can cover the wires from the firewall to the solenoids with the ¼” protective wire cover.

 

                          

 

I installed the rely/resistor housing  under the dash secured with a sheet metal screw and attached the ground wires to the dash sheet metal.   For power I tapped into the fuse box on the left side of the dash and installed one of the ATC fuse holders and a 3 amp fuse.  The control switch is installed into the left side of the steering column cover; I didn’t want it sticking out of the dash.

 

With the switch in the on position the control relay contacts 30 and 87 close and the grid heaters will operate normally giving heated air to the cylinders.   The switch in the off position the control relay contacts 30 and 87a are closed and the ECM signal goes to the resistors mimicking the grid heater solenoids.  No check engine light and reduced electrical load on the charging system.   The switch can be operated on or off before during or after engine start up.  Another added benefit is if your batteries are weak the grid heaters can be turned off saving power for the starter.

Written by:

J. Daniel Martin, Martin’s Mobile Maintenance

AKA IBMobile

12/21/2018

 

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This is how I have done mine about 10 years ago. I just took the 4 factory wires from the solenoids & wrapped them up & sealed them in a plastic bag. I refuse to run a hot wire through the fire wall, especially with all the signal wires from the gauges.

For the switch I use a momentary toggle in the back of my cubby hole. I start by holding it on for a count of 10, release & start engine, then just cycle it like the ECM would do until it smooths out. This will set codes but not set the CEL, besides if you know what the codes are, who cares, you know it's not going to cause any problems.

4 hours ago, jag said:

This will set codes but not set the CEL, besides if you know what the codes are, who cares, you know it's not going to cause any problems.

 The CEL will come on in my truck.  With it on all the time from the disconnected grid heaters then when a more serious problem occurs, for example the crank sensor going bad,  I wouldn't know it until the engine died.   

 

In California, as in some other states, the trucks have to go through some type of inspection.  If the CEL is on, or a code stored, or the monitors not set from a code being erased then it is an automatic inspection failure. 

Remember some places like Idaho in general is not a smog state. But... Ada county and Canyon county is smog areas and are based on exactly what @IBMobile said. Ive spent enough time talking to one guy at a smog station in Boise.

I was figuring for myself to just switch the power leads off of the battery. Just something simple to turn them on and let the ECM regulate until I turn them off. Start the truck, let them cycle a couple few times and then turn them off. That way if I did leave them on the ECM will shut them down before any damage is done. That is Sparky the chicken's idea anyway.

I did something like this to my old IDI.  That was much simpler though, just added and on/off switch to the solenoid wire.  No point using glow plugs in the summer. 

 

 

I might just buy a 200 amp breaker fro the driver side battery and hook up the grid heater to the breaker. Then in the summer just push the button and let it open the circuit. Then in the winter close the breaker. Still, code free method. 

 

@IBMobile is more of in-cab control that doesn't trip the codes. California smog...