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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8813
Experience:  I am ASE Master Truck Certified.
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I HAVE A C-9 2006 SER#9DG04865 IN A MOTOR COACH. IN MY

Customer Question

I HAVE A C-9 2006 SER#9DG04865 IN A MOTOR COACH. IN MY REGION CURRENTLY THE AMBIENT TEMPERATURES ARE 80-92DEG AMBIENT.
AT INITIAL START-UP THERE IS ABSOLUTELY NO HESTITATION ON ENGINE START, HOWEVER, FOR THE FIRST 8-10 MINUTES OF OPERATION, I HAVE "WAIT TO START" INTERMITTENTLY AS WELL AS AUBIBLE WARNING, AFTER THIS PERIOD, NO FURTHER LIGHT OR WARNING. ON INITIAL START I WAIT FOR LIGHT TO GO OUT. I WAS TOLD BY CATERPILLAR THE "WAIT TO START" WAS ASSOCIATED WITH THE AIR INTAKE HEATER. I HAVE BASIC KNOWLEDGE OF THE HEATER CORE AS WELL AS RELAY/SOLENOID, THE COACH IS NOT UTILIZED IN WINTER SEASON, SO STARTING EVENT FOR THAT PERIOD HAS NOT BEEN EXPERIENCED.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.

Thanks for asking your question and requesting me. I will try and help you out.

That is correct. The wait to start is for the intake heater. The heater is controlled by the coolant temp and intake air temp. With it being 80 degrees where you are at. The heater should go off. It should not stay on above 60 degrees. It it is staying on, I would suspect one of the temp sensors are reading wrong and low if the wait to start lamp is staying on. Basically the ECM add the intake air and coolant temp together. When the sum is above 120, it turns the intake heater off.

To verify. You could have the ECM read with a service tool to verify the Temps are correct.

Please reply back if you need more help or have more questions. I am happy to assist.

Customer: replied 1 year ago.
I have a code reader, however, that doesn't explain the intermittency of wait to start flashing on every few seconds during this 10 minute period?
Customer: replied 1 year ago.
Is there an air inlet temp sensor? or what value other than the coolant is being calculated by the ECM?
Expert:  Cat Man replied 1 year ago.

I see. I am suspecting it is blinking as one of the temps are reading low and it takes 10 minutes to get the temp up enough to turn off the intake heater. Can you see the intake air and coolant temps readings with your tool?

Customer: replied 1 year ago.
I'm currently not at site to sample information, however I'm certain those values can be determined with tool.
Expert:  Cat Man replied 1 year ago.

Yes the engine has an intake air temp sensor. The ECM takes the reading of the coolant temp and intake air temp and adds them together. If the sum is below 136 degrees. The heater stays on. If the temp sum is above 136. The ECM turns the heater off.

Expert:  Cat Man replied 1 year ago.

Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.

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