SwedeSpeed - Volvo Performance Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter · #1 ·
Good afternoon forum members,<p>I could use a bit of help here and I've used the search function but don't see this previous issue.<p>1. My brake and center lights don't work at all. All other lights work.<p>2. Behind the ash tray, the #4, 15A fuse checks good and I read about 12.34VDC at the fuse.<p>3. At the brake switch connection, one set of pins reads about 12.49VDC, the other 0.<p>4. With the old brake switch installed, voltage at the fuse reads 0 with brake off (switch depressed).<p>5. With the brake on (switch extended), voltage at the fuse reads about 12.5VDC.<p>6. With a new brake switch installed at the connection (but not in the bracket), VDC reads the same as 4 and 5 above.<p>So my guess is that somehow the circuit is open somewhere between the fuse and the lights.<p>Is there another fuse, relay or connection I should be checking?<p>Thanks in advance for any help you can offer.<p>Cheers!<p>Mike K.<p>
 

·
Registered
Joined
·
1,015 Posts
Re: "95 940T - Brake lights inop (Mike K)

Sounds like your bulb failure relay is bad.<br>It's that big plugin relay in the fuse block.<br>
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #3 ·
Re: "95 940T - Brake lights inop (VolvoBob)

Bob,<p>Thanks for the quick response. As my Chilton's does not show the layout of the various relay's, is it pretty clear with relay that is stuffed back in the cubby hole?<p>Also, do you think it's a pretty common relay that may be available at the local auto parts store ?<p>Thanks !<p>Mike K.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #4 ·
Re: "95 940T - Brake lights inop (Mike K)

I did locate a relay diagram. The bulb failure sensor is the round one in the back left corner.<p>As all my other bulbs work and the bulb failure light, on the instrument panel, doesn't come on, wouldn't this mean that the relay is still good ? <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/confused.gif" BORDER="0"> <p>Any other thoughts ?<p>Mike K.
 

·
Premium Member
Joined
·
19,953 Posts
Re: "95 940T - Brake lights inop (Mike K)

Could be a faulty bulb out sensor (not relay).<p>Does the relay diagram show a brake light relay?<p>George Dill
 

·
Registered
Joined
·
1,015 Posts
Re: "95 940T - Brake lights inop (Mike K)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Mike K</b> »</i></TD></TR><TR><TD CLASS="quote">I did locate a relay diagram. The bulb failure sensor is the round one in the back left corner.<p>As all my other bulbs work and the bulb failure light, on the instrument panel, doesn't come on, wouldn't this mean that the relay is still good ? <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/confused.gif" BORDER="0"> <p>Any other thoughts ?<p>Mike K.</TD></TR></TABLE><p>I had the same problem and just the brake light circuit was bad.<br>If you have cruise control on your car, I bet it doesn't work.<p>In case you want to know, the device has several pairs of coils (so it could be called a relay) one pair of coils is for the brake lights. The coils are wired such that the current throught each create a magnetic field that cancel out.The device senses magnetic fields and if one of the bulbs doesn't draw current (burned out or bad connection) the magnetic field of that coil stops and the other field triggers the device.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #7 ·
Re: "95 940T - Brake lights inop (VolvoBob)

Thanks for the responses.<p>George, <p>If the faulty bulb sensor was bad, wouldn't it cause the other bulbs to be out?<p>Regarding the Chilton manual, the wiring diagram is difficult for me to read. I'll have to look up the symbol for a relay and see if there is one.<p>VolvoBob,<p>You are correct on my cruise control. I never use it and it is also inop. So when you talk of the "device", would this be the faulty bulb sensor ? It sounds like it controls several circuits independently. If so, that may be the problem.<p>Do either of you know if it's possible to check this sensor with a VOM ?<p>Thanks again for your help.<p>Mike K.
 

·
Registered
Joined
·
1,015 Posts
Re: "95 940T - Brake lights inop (Mike K)

As I said my bulb sensor was bad but only the brake lights didn't work.<br>The reason the cruise control won't work if the brake light circuit of the sensor is bad is that the cruise control relies on seeing the brake light bulbs for a ground return. When you step on the brakes 12 volts apears on the cruise input and it turns the cruise off.<p>If you can find the wiring of the sensor you can do a continuity check with a VOM.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #9 ·
Re: "95 940T - Brake lights inop (VolvoBob)

VBob,<p>Thanks for the response.<p>I will check later today. I'll keep you posted.<p>Cheers !<p>Mike K.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #10 ·
Re: "95 940T - Brake lights inop (Mike K)

Guys,<p>We are back in business now ! <p>Replaced the Hella unit. Dealer wanted $175.00 for it. Got it for $80 at my local foreign auto parts store.<p>You've saved me from a potential ticket and accident !<p>Thanks again for your help ! <p>Cheers ! <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/embeer.gif" BORDER="0"> <p>Mike K. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/biggrin.gif" BORDER="0">
 
1 - 10 of 10 Posts
Top