Cruise Control / Brake Light Switch Part Number

Fresh Air Inspector

Well-Known Member
Joined
Aug 27, 2023
Messages
95
Reaction score
33
Location
Yarmouth, NS, Canada
Hello All,

I've managed to gather together most of the bits for a cruise control set-up. However, the brake light switch appears to be a bit of a challenge. According to my factory service manual it has 6 terminals which strikes me as strange. The only part numbers I have been able to find are 'SLS-99' which appears to be an aftermarket item and '2947798' which seems to be a MOPAR part number. The ones available on eBay are VERY expensive and are 4 terminal switches - which makes sense; two for the brake lights and two for the cruise.

Hopefully someone out there can shed some light on the subject.
 

Fresh Air Inspector

Well-Known Member
Joined
Aug 27, 2023
Messages
95
Reaction score
33
Location
Yarmouth, NS, Canada
Hello Volare 1977,

Appreciate the quick response. Unfortunately the link you sent me is for a different part. The eBay item is for the front wheel drive platforms from Chrysler. My car is a rear wheel drive M body '88 Plymouth Caravelle (Gran Fury in the US).
 

AHBguru

Well-Known Member
Joined
Apr 3, 2024
Messages
66
Reaction score
28
Location
WI
4221979 - Stoplight switch w/o Cruise

4221980 - Stoplight switch with cruise

I don't know where you could find the 4221980. Dealer search, Internet search. Most likely the boneyard.
 

Fresh Air Inspector

Well-Known Member
Joined
Aug 27, 2023
Messages
95
Reaction score
33
Location
Yarmouth, NS, Canada
Hello AHBguru,

Thanks for the part numbers - always helpful.

Hello volare 1977,

Thanks for the eBay link - I've purchased the switch, just waiting for it to arrive. :) Interesting that the 'correct' (??) aftermarket part number is SLS-135.
 

Magnum Aspen

Active Member
Joined
Jun 25, 2019
Messages
40
Reaction score
17
Location
Prescott, Az
I used a DPDT industrial control relay with a 12VDC coil in a similar application. I wired the coil of the relay in parallel with the brake lights.

The PCM from the magnum engine needs a "brake on" signal to properly operate the torque converter lock up. One pole completes the circuit to ground to the PCM for the TCC. I used the other pole for the brakes on signal to the cruise control.

I did this because the Aspen brake switch, no cruise control, is a single pole and I needed 2 more poles for the PCM. The donor truck used a 3 pole brake switch.
 

Fresh Air Inspector

Well-Known Member
Joined
Aug 27, 2023
Messages
95
Reaction score
33
Location
Yarmouth, NS, Canada
Hello Magnum Aspen,

Interesting solution to your set-up. I assume you installed an A518 (46RE), transmission with overdrive and lock-up TC. I'm going the same route but using the '95 and earlier A518 (46RH), that uses hydraulics (no electronics :) for O/D and TCC. The company below has a nice solution for the 46RH version.

Lock Up and Overdrive Kit, Dodge 727 to 518 Conversion

For some strange reason on my '88 Plymouth, Chrysler uses a 2 pole brake light switch in 'non-cruise' vehicles and a 6 pole brake light / cruise switch. A separate 2 pole switch for the brake lights and a 4 pole for the cruise. I assume other years had the same set-up.

Thanks for the feedback.
 
Back
Top