SwEm (Safety) Bulletin Number 1 01/04
Attention All Vintage Volvo Owners:
your Brake Lights for proper operation! (Especially on Models:
The original equipment "Brake System Hydraulic Pressure Sensing" Brake Light Switches fitted to these models often become sluggish to operate or fail totally, especially on "Sunday Drive" only, or seasonal vehicles which are parked for extended periods. Brake Lights are critically important for keeping drivers behind you (who are in a position to do real damage), informed of your intention to slow and/or stop. To check their function, with ignition ON, check that your Brake Lights light when slight pressure is applied to the braking system...if it takes jabbing on the brakes or heavy pressure, BEWARE!, it means you will NOT be showing your brake-lights in normal driving situation.
If you are going to drive an oldie, do it safely! DON'T TAKE CHANCES with your car, yourself, or your passengers! Check your Brake Light function often...and please consider upgrading to the MUCH MORE RELIABLE "Brake Pedal Position Sensing" Brake Light Switches as Volvo itself did on the later vehicles (see below). These switches are not only more reliable, but they result in Brake Lights showing earlier, as soon as the pedal comes off its rest position, thereby giving those following the maximum amount of notice of your intent to slow, and time to react.
There are plenty of distractions which keep drivers occupied with things other than paying attention to where they are putting their vehicles...we're not going to change that. Add to that, the increasing number of cars on the road, and resulting decreasing separation between vehicles...we can't change those things either, unfortunately. But showing them our Brake Lights late, or not at all, when those items are under our control, seems like a deliberate compromise of our own safety, when instead, with a simple, common sense, inexpensive solution, we can actually improve our own safety and minimize the risk!...and is safety not one of the reasons we drive a Volvo oldie in the first place?
In the author's opinion, upgrading from the "late-acting" original equipment hydraulic Brake Light Switches to "early-acting", mechanical "Brake Pedal Position Sensing" switches is not an option on these vehicles! It is a significant safety improvement, and therefore required!
Suggested reading: Link to Tech Article Hydraulic Brake Light Switch Failure Investigation
How does one know if vehicle has a Hydraulic or Mechanical Brake Light Switch? Brake Light Switch changeover, from earlier (hydraulic) Brake System Pressure Sensing (located at hydraulic brake distribution block on firewall behind engine) to later (mechanical) Pedal Position Sensing Switch located in pedal box of footwell, took place in 66-67', but this is market dependent, so if vehicle in question is from this year of manufacture range, it's best to check to be certain!
Hydraulic Brakelight Switch in situ at brakeline junction block on firewall.
SwEm "pedal-position-sensing" brake-light switch upgrade kits are available: Link to SwEm Kits page.
Link to: Hydraulic Brake Light Switch Failure Investigation
Additional reading: Brake Light Upgrades