VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1930 Sedan - Vacuum Line Question

I’ve owned my car for going on 10 years and I never noticed the nut and knurled knob on the bottom of my dash next to my steering column. I traced to line out the firewall to my intake manifold and have no idea what it’s there for or what it does. I unscrewed the knurled knob to reveal what is shown in the photos below. I’m guessing it may have something to do with my wipers ? I’ve never driven it in rain so haven’t used the wipers… and no it’s not a trailer queen.. LOL !! Anybody else have this or know what it’s for ?

That is in fact the wiper control. It's simply a needle valve between your vacuum-operated wipers and the intake manifold where the vacuum is being produced. Turn it fully clockwise, wiper is off. Then the more you open it, the faster the wiper runs If your wiper is not working with the engine running and the control open, you'll need to check that there is in fact a vacuum at the wiper motor by disconnecting the hose where it attaches to the wiper motor. If there is a vacuum but the wiper isn't working, you'll need to fix the wiper motor. That is a somewhat delicate operation and should not be undertaken until you're sure you know what you're doing.

The most common problem with the wiper motors is a lack of lubrication. There is a way to draw some light oil into the motor manually to relubricate it, which would be the first thing to try.

Let us know and we can offer further advice. You could also do a search here on this website for other threads about fixing the wipers.....

Hope that helps.

All the Best, Chip

PS -- Also be careful with the control valve -- the body of it is pot metal and is somewhat fragile. They are scarce as hen's teeth and are not being reproduced.

Chip, thank you so much for the quick and informative response. I’ll try the wipers in the next day or so and get back to you on what I find. I have a spare wiper motor, just in case. Thanks for the warning on the Control Valve too.

Happy to help.......

Bob, I can’t remember ever trying your wiper but they vacuum line is in place if I remember. On the valve, bearsfan made me aware that Gary Wallace does in fact have a reproduction valve. It’s different in construction but it can’t be seen under the dash.

On the stock valve, be very careful screwing and unscrewing into the original housing. this is for any of hte components, the needle valve, or either of the vacuum line connections. the body is a pot metal and will easily break/snap, strip !!! the original one in my car looks like someone JB welded the lines in as they broke off the threads. i was able to get an repro from Gary W. it is machined out of aluminum. looks archaic but it works just fine :)

i am attaching a few pictures of a unmolested stock one, has the one line still screwed in but cut off then the repro i got from Gary W.

Thanks Ted and Jerry, the vacuum line is in place and I know I have never tried the wipers and I don’t plan on removing the valve at this time. Thanks for the info, good to know.

If you want to test the wiper motor you can simply connect a vacuum line from the engine directly to the wiper motor.

Thanks Rusty.

My rebuilt wiper motor worked fine when I first installed it a few years ago, however it did not have much power. Now that it has been a few years since I tried it, it is not moving at all. I am wondering if it is just because of the added friction of trying to wipe a dry windshield or maybe there's a leak in the line (possibly at the valve). The motor did seem to be well lubricated when I got it. I may try taking off the wiper blade to see if the motor does run. I have not installed the valve you sold me yet. The old valve was broken and repaired with JB weld.

Chances are the lube has hardened . From previous post it may be possible to put a few drops of ATF in the vacuum line to help loosen it. Possibly moving by hand and then let it sit overnight to work. Worked for me on my 32 .

i was thinking the same thing, the grease may have hardened up. agree a few drops of ATF or 3n1 lightweight oil.

I'll give it a shot, thanks.