I'm working on the same thing. Very little air out the vents, tiny amount of heat, fan motor not happy. The underhood heater water valve is sticky, but works. All three motor speeds work. It sounds like different speeds anyway
I tried the 'core a hole in the side of the heater plenum with a hole saw and shop vacuum trick', compressed air blowing to loosen up the junk, but that didn't work. Not much came out. Too small a hose, not enough suck from my little shop vac, too much junk that was too stuck to the core. Maybe a combination of those. The blower still sounded like a garbage disposal when I turned the fan on, and sounded like the fan was slipping, then turning, then slipping or something. Not much air came out.
Rather than continuing to monkey around, I just removed the entire dash in order to get the heater plenum, and water separator out.
Let me say this about that... When they built these, I'm pretty sure Suzuki started with a heater, then build and over-bolted a truck around it
It's no wonder the most viewed Youtube video under 'Samurai heater removal' is some angry guy chipping, no, smashing his up with a hammer, and removing it in chunks.
Tips: In my '88, the underdash crossbar has to come out. There is a sneaky little bolt thru the firewall, that must be removed from under the hood.
In my case, after I got it completely out and on the bench, I found small rocks and leaves in the fan, oak leaves in the water separator, the heater core's fins were almost completely clogged with trail dust and what looked like dog hair.
I'm glad I gave up and removed the dash, as no amount of vacuuming thru a hole was going to get that stuff out.
My The plastic fan's hub had partially stripped out, probably from getting jammed up by the rocks, which explains why the fan would come on, all three speeds worked, but it would start, stop start, sounded like a disposal, and almost no air would come out on any setting. Other than that, the thing was perfect.
I have a spare used blower and fan, but with this thing being such a PITA to work on, I ordered a new blower motor, new resister, heater core, and hoses.
I salvaged the good fan from the spare blower I have. I also picked up a cowl vent cover (LowRange), to slow down the leaves and junk from getting into the vent and clogging up things in the future.
I cleaned everything up and replaced all the parts and bench tested everything a few nights ago. Not exactly a hurricane, but it moves air, 3 speeds, all the flapper doors work, I gorilla taped up the seams were the foam seals had bitten the dust.
Another tip: You have to check the polarity on the replacement blower motors. These 12v motors are made to run in either direction. Get it backward and the fan spins, but the air doesn't move. I got mine reversed the first time, but it was easy to correct by swapping the wires.
I'll get mine back together this weekend. I hope that's helpful
