2005 GMC Sierra HD evaporator coil cleaning

[Eduardo Guzman]

Need to replace blower fan and resistor switch.

But i need to clean the evaporator coil.

The procedure with the Kool It brand cleaner is not recommended because there could be damage to the resistor unit and the fan motor.

Is there a product that could be used that will not damage the resistor and/or the blower motor.

[Doug_Scott]

Having never cleaned an evaporator core in all my years of a/c repair, I am left wondering why you feel the need to clean the heater box?  Every system I worked on stayed clean as long as the cowl drains were not blocked.  

Since you are concerned with fan and resistor block being damaged when some product is used, you must be talking about cleaning the interior of the HVAC in-dash housing.  If you have leaves packed in there I would use a shop vac with hose adapters to allow small hoses to connect. Some vehicles come with a replaceable cabin filter as well. 

Blower motor resistor blocks are well known to suffer from meltdown issues.  The OEM resistor block is barely the proper design for the current they have to carry. It's not just GM with these issues.