Front and rear heater core questions

[arootbeer]

I'm getting ready for winter down here in Texas, which means I've got about 3 months to get my new '92 Safari sorted out

The AWD was already installed when I got it, and with the new windshield and brakes, it's pretty much ready to go. Well, except for the fact that it has no heat.

My questions are - are the front and rear heating apparatus water lines run in series, or in parallel?

If they're in parallel, which ones are run off of the two lines at the top of the passenger's side firewall, by the relay hanger, and where is the other set?

If they're in series, is it possible to bypass the rear after the front?

The lines that connect to the ports at the top of the firewall are not even bypassed; they're both plugged. Should they be connected together if they're not going to be connected to the heating system, or is being plugged acceptable?

[CaptSquid]

You have WINTER in Texas?????

Seriously, the H-valve by the relays is for the frong heater core only and has no control over the rear heater. The rear heater is controlled by a vacuum which is engaged by the rear heater blower switch. Either one can be run independently.

Sounds like the previous owner discombooberated the heaters. The rear heater runs under the floor.

[arootbeer]

So does the rear heater get hot water from the cooling system or just hot air from the front heater core?

Sounds like I'm in for a heater core replacement...good thing I picked up a manual :P

Is it worth trying to pick one up at a parts yard, or can anybody point me to a good deal on an OEM GM/Delco part?

[CaptSquid]

The rear heater is a water-heated system.

You can get a core at any rep radiator repair shop. But, as always, SHOP AROUND. Use the stealership as a last resort or for GM specific parts. You WILL need a new heater control valve (looks like an H), which is vacuum controlled, for the front core. I can't help you with the rear core.

[arootbeer]

Thanks for the advice. So the heater control valve is just one of those things that you replace when you do the heater core? I have no idea the condition of mine, I'm just asking.

I know I've read on here that the GM parts are supposed to be a bit more friendly to high-flow water pumps, which is why I asked. I'll start looking around and post up any other questions I can come up with.

[CaptSquid]

Replacing the heater control valve is a good idea. At the age of our vans, it begins to weep and seep. Besides, they're cheap.