Heater not working

Here is an issue I have to deal with so I'll throw it out here.

Last summer we sprung a leak in one of the coolant hoses, I couldn't tell you which one exactly , but I believe it was attached to the head and then to a tee. One end of the T went into the firewall( to heater core) and the other end back to the engine compartment. Becasue it's wedged between the engine/intake manifold and the firewall, the access was horrendous, so we removed the whole T to attach a couple hoses freely.

I think the heater wasn't working after we did this repair. (not sure though).. Is it possible that that T was some sort of 1-way check valve and we might have put it in reversed?

Other than that, where else should I be looking?

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sdp
Here is an issue I have to deal with so I'll throw it out here.

Last summer we sprung a leak in one of the coolant hoses, I couldn't tell you which one exactly , but I believe it was attached to the head and then to a tee. One end of the T went into the firewall( to heater core) and the other end back to the engine compartment. Becasue it's wedged between the engine/intake manifold and the firewall, the access was horrendous, so we removed the whole T to attach a couple hoses freely.

I think the heater wasn't working after we did this repair. (not sure though).. Is it possible that that T was some sort of 1-way check valve and we might have put it in reversed?

Other than that, where else should I be looking?

I believe the 'T' is an over pressure bypass. It was a recall item that was installed to preven heater cores from bursting and spraying hot coolant all over the driver's legs.
If you got it in backwards it may be the reason.

Feel the hoses going in and out of the heater (through the firewall), at least you'll be able to tell what is going into the heater core but it could still be the valve by the core or the switch (its electrical you know)- happy hunting