Ok, so I finally managed to start the engine (after a few years) and everything seems semi-OK but the headlight switch didn't bring up the lights. The over-ride switch works fine and the actual lights came on without issue.

I'm fairly comfortable with the vacuum system and it's operation but wanted to run some assumptions past some others before I look too deep.


First off, the switch was working before and on the bench before I reinstalled it and I have no reason to believe it quit (although anything is possible)

Since the over-ride is working, the two hoses must be on the headlight switch, even if reversed, for that to work.


Is there a way of testing if the two lines are reversed without getting to the switch itself?

Thanks
M

 

Absolutely.
1 - Pull the small control vacuum hose off the check valve. Hook up a vacuum pump to it.

2 - Block the vacuum hose after the "T" connection going to the solenoid behind the tachometer. This can be done by squeezing the hose with a vice grip type tool or putting a "golf tee" into the hose end. (If the wiper door circuit is holding vacuum this isn't really necessary, but it eliminates any question about it's condition).

3 - Squeeze closed the control vacuum hose going to the front headlight relays, (again optional, but will save you some pumping).

4 - With the over ride closed, and the headlight switch off, you should be able to pump up the headlight switch circuit and it should hold vacuum. With the h/l switch off, it just transfers vacuum through it. It's when the h/l switch is pull out to the on position that a reversed hose scenario will show itself.

5 - With the h/l switch on, if the vacuum reading goes immediately to zero, the hoses are reversed. Reason is the forward port is designed to allow atmosphere into the circuit now. If vacuum is retained, the hoses are properly routed. Reason is the rear port is designed to block vacuum upstream on the control circuit to prevent a vacuum leak.

This testing procedure mirrors the actual operation of the system, allowing testing of the headlight switch without pulling it out, which can be a real pain as we know. Bottom line, vacuum source hose to the port closest the the pull ****. In line vacuum hose going to the over ride connects to the port farthest from the pull ****.

 

Hello Dave,
As usual an excellent write up.
Thanks again for all your help in the past on my beast.
Any further news on your H/L switches?
Marshal

 

Thanks Dave that sounds like a nice easy check. (wiper door and everything else works perfect)
I'll have a look one night this week hopefully. Off the top of your head, is there anywhere to swap the hoses lower down as a temp bubba fix?
M

 

If your not worried about the color coding of the lines, you could climb under the dash and switch the HL lines at the other end ie... The pull down blue stripe, and tee line white stripe to confirm lines are switched after following Dave's outline above.
Control line has white skunk stripe and if installed correctly comes in from the fire wall off the check valve small port. It then tee's off to the HL port and attaches to solenoid valve on rear of tach.
Rear of tach line has a yellow stripe but still same circuit.
The rest of the lines to the pull down are blue stripe coded.
Marshal

 

Fixing the problem correctly is probably the easiest method. I just put a new headlight switch in a 70 and it took about an hour and I'd never done one before. Half of that time was spent actually removing the old switch. I could swap the hoses in 15 minutes now I know what I'm doing.

 

I'm not concerned about getting at the switch, just have bigger fish to fry right now
M

 

Hey Mooser,

Yea, Marshal is right on. Depending on where your "T" is, swap the hoses there for the vacuum supply. You should then be able to "splice" in another short hose going to the solenoid. Piece of cake........

 

Not far away my friend, not far at all! Should be in production by the end of summer. Don't know 'bout Carlisle though, 1200+ miles one way, I may ship you yours!

 

Shane,

I'm sure a lot of guys would be curious to learn from you how to do a H/L switch swap like that!

 

I did this about 6 month's ago and it's from memory... but...

Disconnect the battery.

Removed A/C duct from under dash. Mine just slide out but I believe there is supposed to be a screw holding it in. I don't know what's under a non A/C cars dash.

Remove the drivers side kick panel (couple of screws).

Drop the steering column by removing the two bolts under the dash pad. This will allow the steering column to lower about 2".

Remove all the dash pad screws, this allows the dash pad to slide out and down to gain access to the headlight switch. Be careful with the dash pad as it's brittle and will break easy. If you need more room you could remove the steering column bolts at the firewall and gain a little more room, I didn't have to do this.

At this point you should be able to reach in with a set of needle nose pliers and swap the hoses.

You can also remove the headlight switch at this time.

First you remove the headlight switch ****, and there is a trick to it. Pull the headlight **** to the ON position. Reach under the switch and there is a small button. Push the button in and than you can pull the **** the rest of the way out. This is really easy if you have a new switch in your hand to see where the button is located.

After the **** is removed you will see a big retainer nut that can be removed with a large flat blade screw driver. Once the retainer nut is removed the headlight switch will slide out.

I also replaced my vacuum control lines at this time. I broke off a golf tee and plugged the new line to the old line. I than reached under the dash and pulled the new line through using the old line. I took about 5 minutes to replace the vacuum hoses.

I replaced the entire headlight switch and vacuum hoses in about an hour and I'd never done it before.