1995 Chevy fullsize Silverado


Heater core making noises

Unread post by WackyWaldo » Fri Nov 05, 2010 2:00 pm

I have a '94 k2500. Last winter (first snow), I started it up and drove to work...when I shut it off, it made a weird 'thunk thunk thunk' sound for about 15 seconds (engine off, key out of ignition). Sounds like it comes from the heater core. Going home, went to start it up and as soon as the engine turned over, it made the same 'thunk thunk thunk' sound. Truck runs fine other than that. Mechanic said he's never heard the sound before, and does not know what it is. Suggested that an air flow flap is off, but can't be sure, he'd have to take the whole dash out to diagnose, before I hand over a grand for what could be a simple fix, any suggestions?


Re: Heater core making noises

Unread post by MeccBoy » Fri Nov 05, 2010 9:24 pm

Without hearing the noise for myself, it would be almost impossible to say. It could be a flap / door for the HVAC system, but this is usually a problem with newer vehicles that have electric controlled doors, yours are vacuum controlled. It would take some crawling around under the dash whn it is making the noise to locate it. Whatever is making the noise may be accesable without removing the entire dash, it is a matter of determining what is causing it before taking it all apart.

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Re: Heater core making noises

Unread post by wildman » Sat Nov 13, 2010 5:46 pm

You can probably diagnose the location a little closer by getting a cheap mechanics stethascope (@$10 at some places) or a rubber hose put to your ear. Pick a part/place and have someone start it or shut it off. When you get to where the noise actually is coming from you'll hear it much clearer. You didn't mention though if your heater controls work through defrost to floor blowing air through the vents accordingly. I'm not sure about that year but some of the older ones used a water shut-off going into the cab- this could make a noise or two if the line was dis-lodged or loose because it would hit. If you can even narrow down the approx. location of the noise- it could save you a bunch in cash
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Re: Heater core making noises

Unread post by Flipper1 » Sun Nov 14, 2010 11:16 am

Try disconnecting the battery for a few minutes. then start the truck and let the A/C system re-learn the door motor positions. this may correct the noise in the dash after they learn the positions again. It takes a fee minutes for the A/C system to go through the door motor actuator positin test.

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1995 Chevy fullsize Silverado

Unread post by craig420 » Sat Nov 15, 2014 2:48 pm

1995 full size Chevy Silverado pick up no dash lights or front corner lights what could it be

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Re: 1995 Chevy fullsize Silverado

Unread post by carriedi » Sun Nov 16, 2014 10:23 am

I would check the fuses first. See if you have power going through the parking lamps fuse ( fuse #9 20A in the fuse box in the lower left of the instrument panel) If the fuse is blown replace it and see if the lights are working after that.

If the fuse is good but you don't have power there, you should look for a problem with your wiring.

If you have power there and the fuse is good, I would look at the power going into the headlight switch (the orange wire) and the wire that goes to the park and dash circuit (the brown wire) It is common for the switch to go bad.
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