My heater core has small leak in it and I think it may be due to electrolysis. I used a DVOM and checked the voltage reading of the coolant and it read -0.12. Is that reading a cause for concern. The heater core was fine until I hooked up my amplifier for my stereo and then it somehow sprung a pinhole leak in the core. Maybe I need to relocate my amp ground wire. Could that cause the electrolysis condition of the coolant. Right now the amp is grounded to one of the tail light hold down bolts in the rear hatch. I am also installing the new heater core and I'm wondering if there are any important instructions before I do it. I plan on flushing the system myself, rather than taking it to a shop and having it pressure flushed. I have new coolant and distilled water and I think that should bring my heater system back to normal.

(The heater core manual said the electrolysis reading should not read more than 0.1-volt. Is the book saying the reading should read more than a 0.1 negative voltage or is that just a dash before the word volt.)

 

I have my ground wire mounted under the seatbelt bracket therefore there isn't any interference with anything

 

its just a dash, the voltage polarity doesn't matter, you can change that by switching the DVMM leads around, its the amount of voltage thats important, you will never get it there, but the closer to 0.00 the better.

make sure all of your motor to body grounds are good, clean & tight along with motor to battery & battery to body grounds.
some of the newer cars have a ground strap on the heater core, it won't hurt if you can add one on your new core, a small hose clamp on the metal part of one of the hose fittings with a wire
under would work if you have the room.

be sure to actually flush it with clean water, not just drain & refill it.
i like to throw in a little baking soda (4~5 table spoons) after i flush a system that had excessive voltage.

 

As far as numbers are concenerned, .2-.3 is about where I start considering a full system flush.

 

Well I drained and flushed the system and installed my new heater core and everything seems to be working correctly. No more antifreeze oil on the windshield and no more antifreeze gas smell in the cockpit either, so I'm confident that it was just a plain ol' defective heater core. Thanks for everyones input. I don't think the voltage in the coolant is high enough yet for concern!