Hello
I've replaced three heater cores in two years and it's getting a little old. I purchased the core from the Ford Dealer ship thinking it would be of good quality. However, the heater core failed twice. Finally, I installed an aftermarket heater core because it has a lifetime warrenty. I read the articals about stray voltage in the antifreeze and the reading was about .01. However, I noticed the reading would spike when the engine was started, about .03 to .06. Does anyone have any suggestions, I've already cleaned a few ground cables and replaced the anitfreeze. In additon, I replaced the rubber hoses going to the heater core and one hose has the restrictor in it. Furthermore,I was wondering if I should ground the heater core to the chasis? I have heard some say not to and other say yes...
Thanks.

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I think your inquiry has been answered in other threads.
The basic issue is a kathodic action of the metals and coolant helped along with the truck power system as you saw when starting.
Unless you eliminate the voltage you see by taking whatever actions are needed, the core failure will continue.
You can see the voltage so take any action to eliminate it.
A spike as you seen is an indicator the truck's DC power is flowing in the core and adding to the issue.
There are no other reasons.
Good luck.

 

The voltage readings I'm getting are below spec with the exception of the starter. In order to get around this I run a ground wire from the starter to the negative battery post. The result is the spike of voltage remained after I run the wire, what else is there???

 

Besides using distilled water for mixing your antifreeze to combat stray voltage I would remove and clean each mounting point for every ground strap on the vehicle. Check your grounds; Engine, body and frame all need to be connected to each other. You might even go further and add extra straps.

Have you read TSB's 01-15-6 and 06-21-19? hope this helps.

 

First off, what's the year/model/engine of the truck in question?

Second off, if your heater core is getting internally clogged and causing the failure, you have problems elsewhere.