Saturn SC2 Heater Core

You should know what this is. If not, you probably roll your windows down a lot.
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Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Saturn SC2 Heater Core

Post by Fast_Ed »

There are decent Youtube videos on the actual process for replacement of this core, but I'll share some of the diagnosis..

The condition was that there was very little heat available in the cabin of the car. Vent temps on cold (~12 degree) mornings would struggle to reach 85F with cabin fan on low and no recirculate. Would drop to 65-70F if I pumped the fan up to high. With recirculate engaged, the cabin fan level made little difference to the vent temps, and the vent temps would climb to a nearly-liveable 100F. Any time the defroster was used, the AC would overpower the heater core and it would become very cold.

Eliminating the blend door as a cause:
Turn heat knob to full cold. Warm up car completely. Turn heat knob to full hot. If there is a noticeable change in vent temp, the blend door is working. The blend door on this SC2 is working. This test could probably be applied to any car, so lesson learned there.

The coolant temp gauge is in the normal range for this car when fully warm; same range as it has been for the last 25k miles. I know that some cars will send the temp gauge to the center of the dial to indicate 'normal.' this car does not appear to do that. Thermostat is not a likely candidate.

So this all points to a heater core. Two choices here: flush or replace. on this car, an aftermarket replacement is ~$40, and a 2-3 hour job. For other cars, it makes more sense to flush. This car received a replacement. Again, check youtube for instructions. And use rockauto for parts!

Result:
Vent temps at ~110F with fan on high on a 12F morning, no recirculate. Recirculate brought the temp up to uncomfortable levels, but surpassing 120F. Defrost no longer cools the car. Low fan speed brought temps up to 125F.

And the car is now comfortable again.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Saturn SC2 Heater Core

Post by kevm14 »

I recommend using a scan tool to see what the coolant temp is doing, both during warmup as well as once the thermostat opens. If that was a problem, I would assume a thermostat would qualify as low hanging fruit to bolster both heat output and improve fuel economy, not that either of those things is "unacceptable" currently but more in the spirit of optimization.
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