The Stovebolt Site Forums The Shop Area Interiors Original defroster vents for 3100 truck

I’m looking for a picture of the defroster vents for a 1950 3100. Are the inlets different diameters?

I'm pretty sure the inlets are the same diameter. I'd have to dig my vents out to be completely sure though.

No, both are the same. Can see example on classicparts.com , look for part number 68-821 Defroster Outlet

I think at Classicparts and everyone else that sells repro parts they are the same. But what about original? I picked up a set with the left side with a 2” diameter and the right side 1.75”. I’ve heard both answers and just trying to get some clarity. In the 70’s I pulled mine out of a car in the junkyard and used the JC Whitney heater. But that’s gone and replaced with a rebuilt fresh air heater.

The ones that I'm sure are original on my '51 were both the same diameter. If I get a chance, I'll get out in the trailer where they're stored and confirm that.
Your "set" may be from a different vehicle (or vehicles).

Kevin, the set I had in there has always worked. I actually thought I had the correct vents. But after my rebuild the vacuum wipers don’t work properly. The control arm for the left side is now hitting the vent. That is what has sent me down this rabbit hole. I have not gotten under the dash to take a good look now that all the gauges are in place. I really don’t want to pull everything apart again. So I’m looking for advice, knowledge, and opinions. Thanks.

If you're all connected up the reason the wiper control arm is hitting the vent is you may have the larger one on the left. Putting it on the right instead might help that. The air doesn't really care how big the hose connection is.
I understand you trying to avoid working under the dash again. Never a happy spot to work in.

For what it's worth, left driver side vent on my truck is 2 inches. The passenger side is missing.

My truck did not have a heater but when I bought the truck it included a spare dash that had the ducts in place and a third duct of unknown origin. All three were the same tube diameter (I am pretty sure) and the one not in the truck measures 1 3/4". Two of the ducts were the same but the other one had the hose connection offset from the windshield discharge end, I presure for clearance of something. Unfortunately I did not keep track of which 2 came installed in the extra dash and which was the loose one. I just received (long time before installing) defrost tubes from Jim Carter and they are 2" diameter but they also include a rubber ring that I believe is intended to fit on the duct to increase it to match the tube diameter.

I dug out my defroster vents and was a little surprised to see that they were different, both in length and the diameter of the nozzle. The longer one has a nozzle that's 2" dia., and the shorter one has a nozzle that is 1-3/4" +/- with a rubber ring on it to bring it up to 2". I don't recall which side they came from but I'm guessing that the shorter one was on the left side to clear the wiper arms. You can see from the cobwebs and bugs inside that they're original. The nozzles on my recirculating heater are different sizes as well, with the same type of rubber ring on the smaller nozzle. The smaller nozzle on the heater points toward the driver's side.
Hope that helps.