Brake light switch for use with silicone brake fluid (DOT 5)

[JoeyD]

Several years ago (2004) in an article in the SDC Turning Wheels, an Harley-Davidson brake light switch was recommended for use in Studebaker's when converting to DOT 5 fluid. I have a 1949 2R5 pickup and have replaced the original equipment switch several times after converting to Silicone, but before reading the article. However, on the H-D forum site, it appears that they are having issues with the switch recommended (HD #72023-51C) and its replacement. Does anyone have any suggestions as to what replacement could be used with DOT 5 silicone fluid?
Thanks, in advance.

[StudeRich]

Your very best solution is to make a bracket that fits under the floor to mount a GM or Ford Mechanical switch so that depressing the pedal releases the normally open switch.

[fatboylust]

As I recall all brake system soft-goods are compatible with all DOT spec fluids, that said, it is the mixing of DOT 5 with DOT 3, DOT 4 or DOT 5.1 where the problem begins. When changing a system to DOT 5 or from DOT 5 the soft-goods may not survive the change due to cross contamination. Harley uses the same brake switches with both DOT 4 (touring) and DOT 5 (everything else). I wish I have the Turning Wheels article to see why the Harley switch was initially chosen. HD 72023-51D Brake Light Switch (replacement for 2004-2005 models, stock for 2006-later models). Of course there is no current recall for a problem on HD products. If you have had numerous problems with system soft-goods since your change to DOT 5 (assuming the system was changed over to DOT 5 and not built anew with it) you may have some residual cross contamination causing the problem.

[StudeRich]

That is probably not the case, because many of us have flushed the heck out of the system OR replaced everything, and still had the problem. Remember that DOT 5 as good as it is, is NOT universally approved by the big three for use in their vehicles, hence no switch compatibility problem, AND when did they last use a Hydraulic switch? 1969?

[JoeyD]

Brake Switch

I started with a clean system, replaced all brake lines, wheel cylinders, master cyclinder etc. Used Silicone brake fluid and in about two months, the OEM switch failed. I replaced it with another OEM switch, and in a few months that one failed. The article was in the June 2004 issue, page 20. The H-D switch part number is 72023-51C.

As I recall all brake system soft-goods are compatible with all DOT spec fluids, that said, it is the mixing of DOT 5 with DOT 3, DOT 4 or DOT 5.1 where the problem begins. When changing a system to DOT 5 or from DOT 5 the soft-goods may not survive the change due to cross contamination. Harley uses the same brake switches with both DOT 4 (touring) and DOT 5 (everything else). I wish I have the Turning Wheels article to see why the Harley switch was initially chosen. HD 72023-51D Brake Light Switch (replacement for 2004-2005 models, stock for 2006-later models). Of course there is no current recall for a problem on HD products. If you have had numerous problems with system soft-goods since your change to DOT 5 (assuming the system was changed over to DOT 5 and not built anew with it) you may have some residual cross contamination causing the problem.

[fatboylust]

You did everything right that is for sure. My Harley has DOT 4 (06 Touring) so I haven't been following problems in the HD DOT 5 world (everything else). The HD 72023-51D switch replace the "C" version for 04-05 and became standard 06 and later. The change seems to be more about the electrical connections than a fluid issue. Still it would interchange. Might be simpler in the long run and go to an electrical switch on the peddle arm and plug the HYD switch unless keeping it original is the bigger issue, good luck; sorry could be more helpful.

[JoeyD]

Original would be nice, but safety is paramount. I will try the "D" series switch, and see how that goes. All else fails, I could try and adapt a later pedal operated switch (or one like on my Model 'A'.) Thanks, and good luck with to '52. Looks like a good car. I have had my '49 2R5 since 1976, and just recently had the little bit of body work done and painted. Now the engine has to be rebuilt! Never ending, but fun.

You did everything right that is for sure. My Harley has DOT 4 (06 Touring) so I haven't been following problems in the HD DOT 5 world (everything else). The HD 72023-51D switch replace the "C" version for 04-05 and became standard 06 and later. The change seems to be more about the electrical connections than a fluid issue. Still it would interchange. Might be simpler in the long run and go to an electrical switch on the peddle arm and plug the HYD switch unless keeping it original is the bigger issue, good luck; sorry could be more helpful.

[Retired]

Install a 45 elbow in the master cylinder with the open end facing up. Install switch. Good to go. Silicon drains away from the switch when not under pressure. Jon Myer solution.

[JoeyD]

Thanks, I will try that.

[stuuder]

Richard,
I thought thats what the residual check valve in the master cyl was for?? 3-6psi for non disc brake applications.
I never had much luck with dot 5 silicone fluid, I eventually installed a mechanical switch as others have mentioned. heres the skinny on fluids....

http://www.gomog.com/allmorgan/brakefluid.html

[Son O Lark]

I went through several Harley D switches before I went to NAPA and got a brand new (Newly manufactured) one. It has lasted for three years now.

[Retired]

I used silicone for a good number of years, replaced stop light switches about once a year untill Jon Myer told me about the 45 elbow. Silicone is very thin and will in time seep from brake wheel cylinders as well. A couple of years ago I could not get the parking brake to hold. Removing the rear drums exposed silicone soaked shoes. My mechanic told me that the front brakes were doing most of the work. New shoes ,rebuilt the wheel cylinders a complete flush of the system and filled the system w/ standard fluid. At one time SI did not guarentee brake components if silicone fluid was used, this maybe their policy yet???

[studesnbldr]

Here is another perspective and experience on silicone fluid usage:
I converted my old daily driver MoPar to DOT5 silicone fluid in 1987.
NEVER an issue with brake light switch failure, leaky wheel cylinders or anything of the sort.
At the time I did the switch I thoroughly flushed everything with denatured alcohol and replaced all the soft parts.
I still own that old MoPar and to this day you can still clearly see the bottom of the master cylinder through the 23 year old DOT5 fluid!
The only brake repairs in covering almost 200,000 miles have been the replacement of the brake shoes; nothing else!
I have since converted several of my Studebakers, some 10 years ago, following the same proceedures and using new (not NOS) switches; not one problem or switch failure of which to speak.
I am very satisfied with the DOT5 and other than a slightly softer pedal, it has worked beautifully, saving me many repeat brake repairs & regular system flushes.
I can only recommend conversion work involving thorough flushes of the metal lines, complete rebuilding of the 5 cylinders and replacement of all soft parts.

[DEEPNHOCK]

Ron Francis sells a silicone compatible switch that has been mentioned here several times.

http://www.ronfrancis.com/prodinfo.asp?number=SW%2D32



Item Number: SW-32Unit Price: $28.95In Stock

[PACKERBACKER]

I have been running it (dot 5) in my Avanti for four years now and I am still using the original switch with no problems. It sure is weird how some people have a major problem using it and others do not. I read that the military has been using it in practically all of their vehicles for years. I wonder if any of their applications use a pressure switch and if it could be purchased by just anyone?