Inlet Air Heater Keeps Cycling On And Off

[smilnjac]

I have a "99 Renegade by Harney with a Cat 3126 engine. its a pusher setup. Air inlet heater keeps cycling. Problem is intermittent. Sometimes I can go 400 miles without it happening and then it may start. Sometimes when it does it the engine will not run at idle. Strange thing is when it does it, if I turn on the Jake Brake it quits or it least it doesn't do it when the engine is above idle. Still might do it at idle like at a stop light. If I turn off the Jake brake it starts doing it at cruise RPM. Naturally engine runs rough when heater cycles (too rich). Cat dealer changed Inlet Air sensor for coolant temp no help,,,,, going back Monday,,,if any one has any experience or ideas, all gladly appreciated.

[wolfe10]

Welcome to the FMCA Forum.

Hopefully someone else has experiences these very unusual issues.

Did the Caterpillar dealer do a download and find any fault codes that would shed light on the cause of the problem?

And ALWAYS when a unique electrical issue, remove, clean and tighten the computer ground stud located just below the computer on the passenger's side of the engine. Have seen some that the chassis maker did not properly secure-- intermittent ground on any computer controlled engine leads to strange issues.

Assume you/they have verifies this is not a gauge issue, but an actual intake heater cycling on even after the engine has reached operating temperature.

That brings up the last question-- is your engine operating at normal operating temperature?

And just a matter of terms, but your Caterpillar 3126 will have an exhaust brake. Yes, it may be made by Jacobs, but is not commonly referred to as a "Jake Brake". A Jake Brake is also known as an engine compression brake and opens the exhaust brake at the top of the compression stroke. And exhaust brake is basically a really strong potato stuffed in the tail pipe-- it creates back pressure on the engine. Ya, it is confusing as Jacobs Corp makes both kinds of brakes.

Please let us know what you/they find.

Brett

[smilnjac]

Hi Brett, Thanks for the reply. When the Cat dealer checked the codes the only one was "Low voltage" to the sensor they changed. (coolant temp). I did not check the ground at the computer, could you give me a little more info on where it is and how to find it ? I am scheduled to drop it off at the Cat dealer Monday. Anything I can eliminate or troubleshoot will help.

[wolfe10]

Locate the computer on the passenger's side of the engine. Right below that is the ground lug.

Brett

[chucknewman]

The ECM in the link below will look very similar to the ECM on your CAT engine.

I have read a post in the past of the same problem that was the result of a defective inlet air temp sensor.

Also the inlet air temp relay could be defective (intermittent contact closure).

The engine electronic/fuel system diagram: here

Chuck

[smilnjac]

Have not solved the problem yet, I have cleaned every electrical connection I can find, nothing has changed other than the air inlet heater light doesn't illuminate anymore. Heater still cycling you can see it in the voltmeter and how the engine runs. Took coach back to the Caterpillar dealer and left it.

[wolfe10]

Thanks for the update.

Please let us know what they find.

[smilnjac]

The Cat service center thinks they have solved the problem. There were some "connector issues" at the ECM, plus they downloaded the latest software to the ECM. Everything was normal on a 10 mile road test, so here is hoping.