To: Volvo303@yahoogroups.com From: Greg David Date: Sun, 15 Feb 2009 16:43:55 -0800 (PST) Subject: Re: [Volvo303] Brake Warning Light Reply-To: Volvo303@yahoogroups.com The TGB has a "dual split triangle" dual circuit braking system as originally used on Volvo passenger cars. One of the sensors that can trigger the brake failure light is triggered by a difference in the pressure of the two circuits. You should check this sensor, as it is likely stuck one way or the other causing the light to come on. Once it is triggered, it stays triggered until you remove the electrical switch part allowing the internal piston to center itself. This was a common issue on 240 series Volvo passenger cars that had a similar dual circuit system and failure sensor. The porcess is documented on page 2 of the linked manual section below. http://www.sorin-having-fun.com/volvomanuals/section5brakes3.pdf Cheers! Greg To: Volvo303@yahoogroups.com From: "Willem-Jan Markerink" Date: Tue, 17 Feb 2009 00:54:45 +0100 Subject: Re: [Volvo303] Brake Warning Light Reply-To: Volvo303@yahoogroups.com On 15 Feb 2009 at 16:43, Greg David wrote: > The TGB has a "dual split triangle" dual circuit braking system as originally > used on Volvo passenger cars. One of the sensors that can trigger the brake > failure light is triggered by a difference in the pressure of the two > circuits. You should check this sensor, as it is likely stuck one way or the > other causing the light to come on. Once it is triggered, it stays triggered > until you remove the electrical switch part allowing the internal piston to > center itself. This was a common issue on 240 series Volvo passenger cars that > had a similar dual circuit system and failure sensor. No parts compatibility, I presume, by your wording?.... ('similar' not being 'identical'....;)) -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] To: Volvo303@yahoogroups.com From: Greg David Date: Mon, 16 Feb 2009 16:28:20 -0800 (PST) Subject: Re: [Volvo303] Brake Warning Light Reply-To: Volvo303@yahoogroups.com --- On Mon, 2/16/09, Willem-Jan Markerink wrote: From: Willem-Jan Markerink Date: Monday, February 16, 2009, 3:54 PM On 15 Feb 2009 at 16:43, Greg David wrote: >> The TGB has a "dual split triangle" dual circuit braking system as originally >> used on Volvo passenger cars. One of the sensors that can trigger the brake >> failure light is triggered by a difference in the pressure of the two >> circuits. You should check this sensor, as it is likely stuck one way or the >> other causing the light to come on. Once it is triggered, it stays triggered >> until you remove the electrical switch part allowing the internal piston to >> center itself. This was a common issue on 240 series Volvo passenger cars that >> had a similar dual circuit system and failure sensor. > > > No parts compatibility, I presume, by your wording?.... > > ('similar' not being 'identical'. ...;)) Not sure... A quick check of VADIS shows two part number variants for the warning valve on a 1976 Volvo 244. 1206854 1273052 The TGB parts manual shows the valvle as: 673764 I'd bet that the 240 valve would work on a TGB if you needed one. It's a pretty simple device. They even list a repair kit for the electrical contact portion. Don't know if they are available new, but there are still a ton of 240's in junk yards the world over. They used these valves on all their cars until the addition of ABS, when they switched to conventional front/rear split systems. The TGB's valve may also be out of a 140 or 1800 series car. They also had the same type of valve. The whole idea of the dual split triangle was to maintain something like 80% of braking ability, even with complete failure of one circuit. That is why the TGB has dual front cylinders and the 240 cars had dual piston calipers with the pistons isolated from one another. Cheers! Greg