3126 intake heater problem

3126 intake heater problem

Posted in the Caterpillar Forum


Antioch, TN

#1 Dec 3, 2010
why does the relay start for two seconds then stop


#2 Dec 4, 2010
It does that always at power up of the ecm as part of the system check.

The ecm checks the air and coolant temperature and then decides if it should stay on or not.

Antioch, TN

#3 Dec 5, 2010
Per thank you for your comment, but the moter isn't actually warm what other sensor could be telling the ecm that the truck is warm

Antioch, TN

#4 Dec 5, 2010
Per this truck will not start without plugging in the block heater no matter what the temperture is .. so how can we maybe check the air and coolant without the ecm? Can we take this ecm somewhere and have it tested? We really need to get this truck fixed
thank you for your time


#5 Dec 6, 2010
The best way is really to hook up Electronic Technician to it and se and see what goes on during a cold start attempt.

It could be a faulty sensor or some other issue with actuation pressure for instance.


#6 Dec 6, 2010
It should be activated for 30 seconds if the sum of air and coolant temp is less than 25degrees Celsius

If the air tempsensor is disconnected it goes on if water temp is less than 40.
It is located on top of the inlet manifold, C967 blue wire.

If water tempsensor is disconnected it goes on if air temp is less than 10.
Located below the inlet manifold, 995 blue wire.

Do you have any check engine light, code lamp or such?
This engine should be able to start without heaters, just more smoke and a little rough in the beginning.

Antioch, TN

#7 Dec 6, 2010
I do not have any codes or check engine light. The truck has always started even on the coldest of days. Now if the block heater is not plugged in no go on the starting.

Townsend, GA

#8 Dec 10, 2011
I have a 3126 Cat marine engine mechanical, 420 hp. The operating temp (gauge) is about 170 F. It takes a long time to heat up and must have high current draw because batteries take a long time to charge over 12V. Any clues as to what my problem might be?

Pittsburgh, PA

#9 Oct 26, 2013
1998 3116 Intake Heater Relay. Keep failing on 4th one. Check heater, had continuity from heater to engine. Replaced Intake heater, lost another relay. Anyone have any suggestions. Heed to know how much Amp draw across poles Thank you Al

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