Would anyone happen to know what the part number is for a brake light switch that has the vacuum break built into it for the cruise control for a '90 740 b234f ?
We ordered one from FCP groton ( and specified that it has cruise control and needs the switch with the vacuum break )and they sent one that only has the electric terminals, no vacuum break, part number 3544691.
This is also the only switch that seems to come up in any of the online parts catalogs.

To make things worse, I just spent about an hour digging through the VADIS parts diagrams and that part number is the only brake light switch that they have listed for any of the 700/900 vehicles until late '95 when they show a 9128577 which I can't tell if that thing has a vacuum break on it or not, it just looks different , but it's not the same shape as the one on the car.

Thanks---------

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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

The GLE's (w/b234f) had a special brake light switch for the cruise control?

I thought all of those era Volvos had a more or less stand brakelight switch that was mounted up high under the dash (and difficult to access) while the cruise control had a vacuum switch (release) that was a little more accessable in the same area above the pedal.

Typical failure of all the brake lights (as well as the cruise control)at one time in the cars is usually the result of a bad solder connection in the big red bulb out sensor in the relay tray under the radio.

Randy

That could be, although I found no reference to a seperate switch for the cruise in the VADIS program, but it wouldn't be the first time that thing has been wrong.
I figured that thing had to be the brake light switch since I took it apart and cleaned and reversed the internal contacts and got the brake lights working.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

It sounds like you know what you have. I was just expressing my surprise at a setup like that.

All of my experience with Volvo brake light switches have been ones that looked like this:



Randy

That's the do-hicky that they sent me, and I dug back in there and , sure enough, there's one buried up in there.
Now for the real confusion, why the heck did cleaning the contacts on the cruise switch make the brake lights work ?
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

I have no idea. I was not aware that the vacuum switch even had contacts. I was working under the assumption it was purely a vacuum release valve.

Are you referring to the device activated by the brake pedal are that is attached to a vacuum hose that eventually leads out to the engine compartment? Are there elecrical contacts on it?

Randy

Well, I finally dug up the wiring diagram and for some odd reason, the vacuum switch shares a wire with the brake light switch and that same wire is the one that goes to the bulb out sensor, so that would explain the bulb out light, still not sure why it made the brake lights work, but it all seems to go together. Guees I need to get a new vacuum switch now and see if I can make that bulb light go out.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

look under group 27 in vadis, ENGINE CONTROL, or 36, other electric equip. I'm pretty sure the cruise parts are listed under engine controls. And yes, the vaccuum switch does get wired in to the circuit buut it has nothing to do with the lights or the warning lamp on the dash. It's only job is to electrically tell the cruise control unit that you are braking, and to release vacuum to the diaphragm at the throttle. The same switch was used in 240/740/940 from about 85 on, you should be able to find dozens at the salvage yard, they rarely fail.

According to the wiring diagram, they two switches share the wire that goes to the bulb out sensor. At this point, I'm assuming that the bad contacts in the vacuum switch are contributing to an excess resistance reading and throwing the bulb sensor off. I know that the Vac switch has bum contacts, so it needs to be replaced anyway. I'll get that variable out of the way before I go chasing any other gremlins.
Thanks for the location in the VADIS, THat should get me on the right track.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

Are you sure there is anything wrong with the vacuum switch?

They are easy to check by applying a vacuum to the hose and pushing the brake pedal to see if it releases vacuum. For testing purposes simply apply a vacuum by mouth.

The bulb out sensor circuit is a pain. Have you tried clean the bulbs and associated sockets? The bulb out light relies on a differential in current flow to set the light. Sometimes changing both bulbs will rememdy the situation.

Randy

The vacuum part of the switch is fine, but the electric part of it was dead before I opened it up and flipped the contacts and cleaned it up, now it has continuity, but not perfect, it's still a weak connection.

I went through every connector and socket on the brake circuit and cleaned and tightened everything up, but no difference.
Now that I've seen the wiring diagram, I'm pretty sure that that shared wire is giving an excess resistance reading to the bulb sensor.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

Actually, it just occoured to me that somewhere along the line, somebody must have hooked the wrong sets of wires up to those switches. THat would explain the brake lights running off the vacuum break switch
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

Yes, the vacuum release has 2 electric contacts, and the wire colour coding is different that the ones going to the brake switch so it doesn't look like they loop through.

A while back I disassembled the vacuum switch and it has an extra set of contacts inside, so I cleaned it up and turned the head to use the clean contacts and the brake lights started working.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

The vacuum valve is indeed shown with engine controls in vadis group 27, part number 1367159. The brakelight switch is shown with the brake pedal and is pictured in on of the posts, part #3544691.
If the bbrake lights are wired to the cruise vacuum switch, then someone has cut and spliced the conectors, cause the terminals on the switches are way different. again, the switch with the vacuum valve and wires has nothing to do with the brake light operation.