Heater core shape?

The outlets changed from the early design (left) to the late design (right) for the '94 MY. Here are a few part numbers for the late design:

Grog6 said:

If you ground ALL parts of the cooling system together it will not corrode. Block, radiator core, and heater core. The radiator core is not grounded in our car except by accident, unless you do it yourself. That's what most people miss.

Click to expand...

Exactly. My genuine theory is they were concerned technicians would fasten the other end of the wire to a poor point contact that wouldn’t stop the electrolysis, so rather than risking a return visit from the same customer armed with a complaint their core failed despite their touted repair, walking back the TSB on paper all gets the stealership off the hook, and rake in the hours for another heater core job

I mean the previous TSB tells the technicians to ground it to an “EXISTING FASTENER”, nothing specific since it applied across models, it’s up to the discretion of the technician doing the job. So let’s think of existing fasteners in the closest vicinity of the heater core on our cars - the studs for the heater box instantly come to mind… insulated! As are a few nearby bolts on the plastic wiper cowl. It’s basically a 50/50 shot you’ll pick an existing fastener that has direct contact with the grounded chassis steel, if you’re on the clock and unfamiliar with the car you won’t necessarily know unless you checked continuity/resistance with a meter

As long as you don't drill thru a tube, there's no danger. A copper wire touching a stainless ho se clamp is going to corrode in winter driving. A good ring terminal is tin/lead dipped, or at least, the 30 yo box I have is. It helps a lot. Galvanic corrosion is a *****, lol.
To eliminate it, requires extreme measures. So, just inspect and replace as necessary. If you replace the coolant every two years, you'll never have a problem, three years is too long, from personal experience. If it turns brown, it has boiled, and needs replaced.

Here's the table; the further apart right-left, the higher the potential. To eliminate the corrosion, you have to remove the voltage, or the electrolye. Rainwater is mildly conductive, but you add salt, you have an unwanted battery.