2003 Sonoma No Heat

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only1jw
Posts: 1
Joined: Fri Oct 19, 2012 2:27 pm

2003 Sonoma No Heat

Unread post by only1jw » Fri Oct 19, 2012 2:47 pm

Suddenly I have no heat only cold air. Checked the HVAC fuses all good. Coolant level full with new radiator and water pump. Any suggestions on where to look next?

Thanks for the help!

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ProTech
Posts: 651
Joined: Wed Oct 17, 2012 10:08 am

Re: 2003 Sonoma No Heat

Unread post by ProTech » Fri Oct 19, 2012 6:08 pm

The Sonoma's and the S10 pickups had a bad tendency for clogged heater cores. Unless your no heat issue is an immediate result of replacing the water pump and radiator, in which you probably just have an air pocket, you're going to have to do some checking. There was a service bulletin a few years back for those trucks where you had to acid flush the cooling system, back flush the heater core and install a new thermostat. You may need something like this. Give a feel to the heater hoses once the truck has reached operating temperature. Both should be very hot to the touch. If only is hot and the other is cold or just lukewarm, you definitely have a restriction in the heater core. Usually taking the hoses off and doing a back flush through the heater core is sufficient. Worst case scenario, if it is extremely clogged and unable to be cleaned out, you'd have to replace it. If you don't feel that is the issue, check to make sure you don't have a large air pocket in the cooling system...OR a bad thermostat...OR internal engine problems like a head gasket issue.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

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