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Ivan
Ivan, ASE Certified Master Technician
Category: Chevy
Satisfied Customers: 4871
Experience:  ASE Master Tech. 20+ years experience. 9 years self employed. Expert on AUTOLAB Radio Show
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2005 trailblazer lt: heater..car dies..when i am driving..loses power

Customer Question

i have a 2005 trailblazer lt and when i turn the a/c and heater on the car dies..when i am driving and i turn the a/c or heat on it loses power....what is causing this
Submitted: 6 years ago.
Category: Chevy
Expert:  Ivan replied 6 years ago.

Hello and good evening. It sounds like the air conditioning compressor is starting to seize up. If it's enough to burden the engine when cruising, it is certainly enough to cause it to stall when at idle. On the compressor itself, with the truck off, see if you can turn the center of the compressor pulley be hand. That is the actual portion that is connected to the compressor. If it very stiff to turn, the compressor is to blame. Let me know what you see.

 

Your JA Expert,

Ivan

Customer: replied 6 years ago.
where is the air compressor so that i may try
Expert:  Ivan replied 6 years ago.

When you are looking at the engine, this will be located towards to lower portion of the engine on the driver's side.

 

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Customer: replied 6 years ago.
do we turn the part that has the bolts in it...if so it turns and its not tight....but it has a belt around it aswell.......would it be a vaccum hose leak
Expert:  Ivan replied 6 years ago.
The part right on the front. It has a center bolt and spins independent of the pulley. That portion will turn easily. I don't mean totally loose, but loose enough that you can turn it with one hand.
Customer: replied 6 years ago.

it turns

 

Expert:  Ivan replied 6 years ago.
Ok, I would like you to see if you can do this, unplug the electrical connector on the front of that compressor. It will be right behind the pulley. Then start the truck up and turn the a/c on and see if you feel anything. The compressor will not turn on, but the rest of the components will. I would like to see if the compressor along is the variable or if something else may be.
Customer: replied 6 years ago.
it still dies
Expert:  Ivan replied 6 years ago.
Ok, then lets try this next. If the throttle plate was very dirty, it would cause the engine to stall at idle. Never off idle or under cruise, but at idle. If you follow the tube that goes from the air filter to the engine, it will go to a black air box. Remove that air box and you will see the throttlebody. As air passes through the air filter it goes through the tube into the engine. As the air passes the throttlebody it deposits dirt to the back of the throttleplate and to the surrounding housing. When this accumulates, it blocks off the airflow that would normally pass it and the engine will stall. Obtain a can of throttlebody cleaner or carburetor cleaner and a brass brush. Open the throttle plate by hand and spray the throttle plate and the housing around it with the cleaner. Then scrub it with the brass brush. Spray again and wipe it clean with a cloth. Reassemble and don't be alarmed with it starts a little rough, it will, then it will clear up. See if it feels better. If it does, reconnect the compressor and see if it is still good. If so, you will be done. Keep me posted.
Customer: replied 6 years ago.
i will have to try this in the morning but i will keep you posted and thank you so much. i will prolly be talking to you tomarrow....thanks michael
Expert:  Ivan replied 6 years ago.

You are welcome Michael. Let me know what happens. Have a good night.

 

Ivan

Customer: replied 6 years ago.
okay we did the cleaning and it is still doing the same thing.....i watched the compressor as the car was running and it would turn then stop the engine would die down to almost dead then the engine would pick back up....with it doing this the compressor will then start turning after the engine idles
Expert:  Ivan replied 6 years ago.
What happens if you unplug the compressor?
Customer: replied 6 years ago.
its unpluged and it idles like it should and it does not try to die anymore
Expert:  Ivan replied 6 years ago.
Ok, so we are getting closer. With it idling, I would like to to turn the headlights and the fan for your air conditioning while leaving the compressor unplugged. Then with all of that on, put your foot on the brake and put the truck in drive, let me know if it still feels stable through all of that.
Customer: replied 6 years ago.
idles like it did when we bought her
Expert:  Ivan replied 6 years ago.
Ok, then do this, reconnect the A/C, take it for aXXXXX During that drive, turn the A/C on and drive with it on for a bit, then shut it off. After you return, see if the truck will idle properly with the a/c on.
Customer: replied 6 years ago.
it did great but when i pulled into the driveway it did the same thing
Expert:  Ivan replied 6 years ago.
Ok, I'm going to do a little checking to see if there is something that will take attention away from the compressor. I'll get back to you in a moment.
Expert:  Ivan replied 6 years ago.
Do you have any check engine light?
Customer: replied 6 years ago.
yeah it is on'
Expert:  Ivan replied 6 years ago.
Great, that will be a clue. Large parts stores like Autozone and Pep Boys offer code retrieval for free. See if you utilize that offer and have them scan the codes. Let me know the code numbers they find and that will point us in a direction. Right now, I'm feeling we have either a bad compressor or a bad throttlebody, but let's see what code is there and I'll have a very good direction on where we should look.
Customer: replied 6 years ago.
they said that a map sensor....and a camshaft position sensor is also bad
Expert:  Ivan replied 6 years ago.
What were the code numbers?
Customer: replied 6 years ago.
he would not give me them.....he just wrote down what was bad
Expert:  Ivan replied 6 years ago.

That is very nice of him. Here is what I would like you to do first. Get a volt meter. Unplug the map sensor and measure the voltage you find on the 3 wires going to the map sensor. Do that again with the 2 wires on the camshaft positioning sensor. I want to make sure we have the proper reference voltage on one of the wires at each sensor. Here are pictures of their locations. They are easy to get to. Without the codes numbers, I can't be exactly sure what error the computer is seeing, but let's try this. If it comes down to replacing these two sensors, they are easy to access.

 

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