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sailor_lou · 06-12-2017, 08:52 AM

I have a CAT C-7 (350 HP) in a Travel Supreme motorhome with a check engine light illuminated due to the following codes:

70-5: Inlet Air Heater Driver #1
729-5: Air Intake Heater Open Circuit

I checked the grid heater solenoid and it is good, but it appears I am not getting control power to the solenoid. I have read in a few places the 12 VDC power should be there and the ECU completes the ground when the heater is energized. Is this true? Where does the power for the solenoid come from?

I purchased the schematics from Spartan (chassis manufacturer), but they do not show the grid heater circuitry. Any help would be appreciated.

Thx,

Lou

Cat · 06-12-2017, 04:40 PM

Whats your engine serial number I'll look up your engine schematic. Check the resistance of your heater grid by its self- unhook your power wire going to the heater from the solenoid. Then take a ohm reading from the power in to ground ---sounds like its open in your heater grid is broken /open. Still give me the serial number.

sailor_lou · 06-13-2017, 06:43 AM

The engine S/N is KAL50664. I will check the heater resistance, but even if it was open shouldn't the heater solenoid still pickup when the conditions are met for the heater to energize? Also, is it possible to purchase a set of schematics for my engine?

Thx for your help,

Lou

Cat · 06-13-2017, 02:15 PM

Yes by the schematic power on this serial is supplied from the coach to the heat bulb and to the solenoid. The ECM does ground the wire--- if it is the combination of temperatures are correct to energize the solenoid and power the grid. If the engine ECM sees an open on a circuit it will not energize that circuit----its protecting it self from a short.
But by the schematic there should be power from supplied from the coach. See schematic trying to send it where you can read it. If you want the whole schematic Cat will sell you just the schematic----- they would have to order it. I hope you can blow it up to read. The section to the left is the coach side-- the one to the right is the engine side ECM. Hope that helps.

sailor_lou · 06-14-2017, 06:28 AM

Thank you, thank you, thank you !!!

Although a bit difficult to read I am able expand the pic enough to make out the interconnections. I think this info, along with the wiring diagrams I received from Spartan, will allow me to continue on with the troubleshooting. We leave the rig in NH (where we will be moving to soon from CT) so hopefully I'll get up there next week to check things out. I will contact CAT to order a set of wiring diagrams, but this should get me through for now. I'll let you know how I make out.

Thx again, your knowledge and efforts are truly appreciated.

Lou

Cat · 06-14-2017, 08:29 AM

You're welcome. Good luck. I look forward to seeing what you find is causing the problem.

slemnah · 06-16-2017, 05:01 AM

Cat, just wondering how you are able to pull up schematics and if I can get a copy of the engine schematics for my 2005 C13? My engine # KCB21422. Thanks

Cat · 06-16-2017, 09:08 AM

KCB wiring schematic. I had to put in to two screen captures. On our ECM there are two large connectors. One schematic is for the wires that go to one connector the schematic is for the other plug. Hope it helps.

slemnah · 06-16-2017, 10:19 AM

Thanks, I really appreciate it

gatorcq · 06-17-2017, 05:37 AM

there s a separate 125(maybe 150) amp CB that feeds the air inlet heater coil. Look on the frame rail, passenger side.

sailor_lou · 06-17-2017, 08:05 AM

Quote:

Originally Posted by gatorcq

there s a separate 125(maybe 150) amp CB that feeds the air inlet heater coil. Look on the frame rail, passenger side.

Thanks, that breaker is good and I have heater power to the contact side of the solenoid, it is the control power (solenoid's coil) that is not there.

gatorcq · 06-17-2017, 08:41 AM

That comes from ecu. Check the pin connection

Cat · 06-17-2017, 05:03 PM

By the schematic power to solenoid comes from the coach on the 957 red wire . The other side of the sole goes to the ecm wire 850 blue which grounds the wire to engage he solenoid.. Just for test purposes could you run a jumper from the main grid power on the solenoid to the connector that you should have battery power on the solenoid pole then turn the key on and see if the grid heater works. Its going to have to be cool enough for the computer to turn on the grid though. And you would have to monitor the grid voltage to see if it comes on. Because the power for control side of the solenoid and the heater light get power from the same source on the coach--so the heater light might not come on even though the grid heater did.

sailor_lou · 06-18-2017, 09:56 AM

Quote:

Originally Posted by Cat

Just for test purposes could you run a jumper from the main grid power on the solenoid to the connector that you should have battery power on the solenoid pole then turn the key on and see if the grid heater works.

If I cannot find the normal source of the power (hopefully a relay issue or a blown fuse/fusible link somewhere) that is exactly what I was planning on trying. I'll also fuse the jumper in case there is a short somewhere.

Thanks to all for your thoughts and suggestions.