Hi all,

I was driving my '78 yesterday and turned on the defrost. I noticed air is only coming out of the passenger side. I'm assuming that means the hose on the driver's side has a crack in it or something to that extent. I am assuming changing that hose is a absolute nightmare but wanted to check before I even opened the car door.

TL;DR: Is changing the driver's side windshield defrost hose a nightmare/very involved?

There is not much room on that side inside the dash to route the piping.

The piping could be unhooked from the the defrost end.

It could be crushed in the dash.

Unhooked at the heater box end or have a hole.

I'm going to guess it's unhooked on one end. Even crushed it should blow some air

50 minutes ago, Patcon said:

There is not much room on that side inside the dash to route the piping.

The piping could be unhooked from the the defrost end.

It could be crushed in the dash.

Unhooked at the heater box end or have a hole.

I'm going to guess it's unhooked on one end. Even crushed it should blow some air

It being unhooked would make sense since there was absolutely no air coming through. Is the area its connected to easy to access or does it require any disassembly to reach?

I have my center console out right now but this shows the defrost hose as it attaches to the blower housing in the 260/280. The 240's are similar. My hose is not original. Okay, I'll do the dusting before I put the console back in...

The blower end of that hose is basically just above the transmission tunnel and at the rear end of the blower box - which means it's almost to the center console front. That's fairly easy to see once you get down on the floor. Everything is a bit crowded on that side of the dash but once upside down under the dash you should be able to see or feel it all. The hose isn't very long and it goes straight up into the plastic "diffuser" piece. If it was disconnected from the blower housing you'd probably see it hanging loose near your calf as you sat in the car - and you'd feel the defrost air blowing sideways into your leg.

Edited January 24Jan 24 by cgsheen1

6 hours ago, cgsheen1 said:

I have my center console out right now but this shows the defrost hose as it attaches to the blower housing in the 260/280. The 240's are similar. My hose is not original. Okay, I'll do the dusting before I put the console back in...

The blower end of that hose is basically just above the transmission tunnel and at the rear end of the blower box - which means it's almost to the center console front. That's fairly easy to see once you get down on the floor. Everything is a bit crowded on that side of the dash but once upside down under the dash you should be able to see or feel it all. The hose isn't very long and it goes straight up into the plastic "diffuser" piece. If it was disconnected from the blower housing you'd probably see it hanging loose near your calf as you sat in the car - and you'd feel the defrost air blowing sideways into your leg.

Now hang on - mine is definitely not plugged in, I always thought that was where the hot air was supposed to come out when you turn on the heater! Where is the heat actually supposed to come out then??

7 minutes ago, Zed Head said:

Interesting - in that case my 78 sends heat out of that defroster port regardless of if it is on heat or defrost. When I move the slider from recirc heat to defrost, it is definitely moving something though, which is strange.

Yup, 12. There's a door closer to the firewall that is heat to the cabin - pretty much right in front of the defrost port. It flaps up and down - well swings from closed to partially open anyway (on the 240 it's controlled by a cable - I don't remember on the 260/280...). Warm air on your feet... I have a blower box in the garage. I'll see if I can pull it out and get a pic or two. I think maybe closing that might be what diverts air to the defrost.

Edited January 25Jan 25 by cgsheen1

7 minutes ago, cgsheen1 said:

Yup, 12. There's a door closer to the firewall that is heat to the cabin - pretty much right in front of the defrost port. I flaps up and down - well swings from closed to partially open anyway (on the 240 it's controlled by a cable - I don't remember on the 260/280...). Warm air on your feet... I have a blower box in the garage. I'll see if I can pull it out and get a pic or two. I think maybe closing that might be what diverts air to the defrost.

interesting, thanks. it sounds like the unplugged/potentially missing hose is the issue.

I don't have a vacuum bottle or solenoids in my Z. I could have sourced them over the years, I may even have everything stuck in a cabinet somewhere. BUT, all I've ever been interested in is the A/C - SO I've never bothered with it OR the vacuum lines or solenoids under the dash because the HVAC system defaults to typical Air Conditioning settings: Air out the dash vents and cabin air recirc - not fresh. I'm an Idaho boy so Arizona never really gets cold enough for me to use the heater - good thing because my core leaked nearly as soon as I had this back on the road 13 years ago. I've never bothered replacing it.

BUT, there's an excellent description of all the vacuum line connections to the distribution block and how each mode functions in the FSM. It's in the Air Conditioning section - if you don't have A/C just ignore those parts - the heat and defrost and recirc and fresh air, bi-level, mode doors, solenoid operation is all in there.

Wow this is a lot more straightforward than I expected. I just took the below picture, you can see the defrost hose outlet (top) and the vent inlet (bottom) definitely missing its hose, with the heater core outlet vent open. Looks like I have a hose to buy, thanks all!

Update for you all - I purchased a Dorman 96034 (for anyone with the same issue) and was able to slide it right on. The driver's side is incredibly easy and didn't require removing anything to install the hose - the passenger's side looks like an absolute nightmare - so I lucked out.

Thanks for the help

Edited February 22Feb 22 by chaseincats