Dave Fox

For anyone considering replacing a clogged heater core, at least try unclogging it first to save a lot of work. (This suggestion of course is not for those with a leaking heater core.) My heater core in a 1986 Subaru GL with 250,000 miles was so clogged only about 5% or 10% of the coolant flow and heat transfer occurred. The barely tepid air temperature at the heater outlets wasn't enough to defrost the windshield. I had tried pressure flushing the core with plain water with no effect. 10 years of nearly no heat haunted me until this year. But I finally fixed the clog by removing both heater core hoses from the engine, filling them and the heater core with white vinegar, and draining the heater core and flushing it after 18 hours. That dissolved whatever had clogged the heater core. Now when outside temperature is about 30 degrees F, I can get hot air out of the heater vents when the car is idling at up to 180 F measured by an infrared thermometer. Now the Subaru is toasty warm on cold winter nights.

"When you replace your pump, keep in mind that the fuel pump may get power when the ignition is switched to 'run', pump for about 1-1/2 seconds, stop and wait for an 'rpm' signal. On my 87, there is a rev. sensor between the ignition switch and fuel pump. The fuel pump resumes pumping when the engine is running. Not sure about your 86." Thanks for advice. I didn't know where to look for any rev sensor. My '86 GL occasionally (once per year) runs for 30 seconds and runs out of gas when the fuel pump turns off after just starting the engine. This problem can last for a day or two; what a nuisance at first! One work around I discovered is to slightly rotate the ignition switch from the "run" position towards the "start" position, but not enough to actually engage the starter. It isn't happy being engaged when the engine is already running. Then when rotated 1/2 way between, a contact in the ignition switch provides power for the fuel pump bypassing that rev sensor apparently. The downside of this tactic on rainy days is that while the engine runs, the wipers don't while the ignition switch is in this slightly-rotated position. Use Rain-X then. I discovered this ill-advised-but-workable-solution when the return spring on my ignition switch broke and conveniently the switch would remain in that fuel-pump-on-regardless, half-rotated position. To know just when that ignition switch is rotated far enough but not too far, I installed a 12v indicator light on the dash with wires in series with the fuel pump's supply wiring to let me know when the fuel pump is receiving 12v of power. If once per year or whenever that dash light is unlit, I know that I need to slightly rotate the ignition switch to supply power to the fuel pump until things clear up again. Maybe the rev sensor, wherever it is, is wonky? Since the problem only occurs once per year, I've had little incentive to look for that rev sensor. One hopes that in a year or so a newer car will take its place. But the Subaru just keeps on running. Sort of.

The spring inside is likely broken; that happened in my '86 GL. Either buy a switch for ~$60 +/- and spend the hour to replace it or manually twist the key to the ON position each time manually.