Heater core leak

I just pulled my 94 M35A3 from it's winter hiding spot and found that I have a heater core leak, leaking into the cab. Has anyone ever had to pull one of these apart and if so, is it a big deal to do it?
Also, and don't shoot me if this is a dumb question, is there a fan speed switch for the heater on my unit somewhere or is it just on and off?

Thanks!

SaskCanuck said:

I just pulled my 94 M35A3 from it's winter hiding spot and found that I have a heater core leak, leaking into the cab. Has anyone ever had to pull one of these apart and if so, is it a big deal to do it?
Also, and don't shoot me if this is a dumb question, is there a fan speed switch for the heater on my unit somewhere or is it just on and off?

Thanks!

Click to expand...

Every one of the trucks I’ve had (4) eventually needed a heater core. Depending on where’s it’s leaking it’s an easy fix. Should have a switch left hand side below steering column , high ,off ,low.

My truck's heater core leaks too. Until I can pull it out, I have its water control valve disconnected and tied shut with some bailing wire. It hasn't leaked since. I haven't needed heat either though But I do want a working heater someday!

It's my understanding that the cores were overcrimped somewhere when manufactured, leading to a leak.

From my recollection of the TM's instructions, the cooling system should be drained before the core is pulled, so this is a good time to replace the coolant if it hasn't been done in awhile. The glovebox also needs to be removed, which gives you an opportunity to clean and paint it. The fan needs to be disconnected. I can't remember if the box and core come out as an assembly or separately.

SaskCanuck said:

Also, and don't shoot me if this is a dumb question, is there a fan speed switch for the heater on my unit somewhere or is it just on and off?

Click to expand...

The fan speed switch is a 3-way toggle switch located on the dashboard to the lower left of the steering column. It is two-speed with an OFF position in the center.