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I have a 94 940 non-Turbo with what I believe is an airbag problem:
90% of the time when I start the car the SRS light will stay on, and the car will run off the battery until it dies if I don't alleviate the problem. I found out that by hitting the front of the passenger side airbag, the light goes off, and the alternator kicks in. I don't remember how I found out about this fix but it works. Most of the time a gentle tap will do, but sometimes I really need to hit it hard a few times until the light goes off. Interestingly, the temperature gauge stopped working one of the times when I had to hit the airbag a little harder than usual. Not sure why as they are on opposites sides of the dashboard. I have removed the glove compartment to check for loose wiring etc, but all appears to be tight and ok.
Any help would be much appreciated.
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Dear Volvo Mystery Sleuth,
Hope you're well. I just tried to submit a detailed post, to help you.
The post didn't make it.
I don't know why.
Yours faithfully,
Spook
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Spook,
Thanks for the advice on the SRS light issue. After cleaning the wiring contacts on the alternator, and removing the glove box to check for loose connections, the light did not go on for a few weeks. However when I replaced the glove box last weekend the light came on the next time I started the car, and has been on and off since, which I would assume indicates some issue or loose connection around the airbag that was triggered again when I replaced the glove box. I'll keep looking.
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I think you'll find Spook is on the right about a missing D+ alternator signal from a bad connection at or in the the instrument cluster that's reponsible for lack of charging. A more common charging problem might be a worn brush/regulator pack in the alternator, but thumping on the dash should do little more than calm your angst, not cause a warning light to go out.
Because you just say the SRS warning light (not the alternator charging light) and thumping on the passenger side of the dash makes a difference, then I will mention that there's a ground screw on the airbag above the glove box that can be problematic for the SRS warning light, but not so far as I can imagine for alternator charging. The passenger side airbag ground screw is just a threaded screw that extends out from the airbag assembly to touch a ground strip attached to the dash structure. If that screw is not extend all the way, or if the end should somehow become corroded, and only makes intermittent contact then it will raise an SRS diagnostic code. If you suspect this possibility then check the OBD section here in the FAQ and read out any error codes from the SRS system from port 5 of connector B. Anything other than a 1-1-1 code will indicate a detected problem, such as a 2-2-2 code for a bad connection at the passenger side airbag. You can alway try resetting the SRS diagnostics -they will soon return if the problem persists.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Dave,
I think you may be correct on this. On the advice of both you and Spook, I cleaned the wiring contacts on the alternator, and took the glove box out to see if there were any loose connections around the airbag. Afterwards the car ran for a full two weeks without the SRS light coming on. However, after putting the glove box back on, the light came on the next time I started the car, and has been on and off intermittently since, indicating to me that the problem is in the wiring or the ground wire around the airbag. I will take out the glove box again this weekend and investigate further.
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Yes, based on what you're saying, I'd be very suspicious of the aforementioned ground screw on the passenger airbag module.
Let me begin with the usual SRS cautions and a disclaimer. Before playing with any airbag wiring Please DISCONNECT THE BATTERY negative terminal to make sure the SRS control module (uner the driver seat) is disabled. Wait a few minutes (like maybe 20+ just to be safe) to make sure the internal capacitors are adequately discharged. NEVER USE A CONTINUITY TESTER OR OHMMETER ON ANY CONNECTOR TO AN AIRBAG, stray voltage and even static discharge can, in theory, trigger an airbag deployment. No matter what, always keep your head out of the bag deployment zone. Work around SRS systems presents added risks of serious injury and requires a certain level of competence and confidence. If at all in doubt, leave it to someone more qualified. Any work you do is done completely at your own risk, not anyone associated with brickboard.com, and most especially not me.
You shouldn't need to open up any of the SRS connectors, in fact this could be a very easy fix. With the glovebox removed, just carefully look under the airbag. You're looking for a long ground screw on the airbag module mounting assembly. It just threads through the frame and the tip touches up against metal. As I recall, there are no wires to it and it's in the very middle of the assembly. Once you find that screw, just back it off a few turns and then tighten it back in snugly. That should fix it. If you see any hint of corrosion then be sure to clean it up first, ideally protecting it with a little dielectric grease or DeoxIT paste.
Now, if I'm right, this deserves a double Thumbs Up as this is one rare occurrence and you just happened to say the right words to trigger a very old memory.
Let me explain that I only know this by virtue of once having had an airbag replaced by a dealer related body shop that I quickly learned to distrust. A couple of weeks later, the SRS light started coming on, much like with you. The OBD code led me to the passenger airbag wiring. I quickly determined that ground screw wasn't even finger tight. A few good turns of the screw quickly fixed the problem. That was 15 years ago, no problems since and I've never heard of it with anyone else.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Dave,
Spent a few hours this weekend looking for the ground screw or any loose connection for the passenger airbag. Did not find either one. It does not appear that there is any ground screw anywhere in or on the mechanism or anywhere around it. All connections appear to be tight. Still, my gut feeling is that you are correct and there is a ground issue or loose connection somewhere around the passenger airbag. I even checked the wiring under the seat, although it was very hard to access, but quick a visual looked like everything is in order. After I reconnected the battery and started the car, the SRS light stayed on. A quick tap of the front of the airbag shuts it off. I have noticed that the warmer it is the less likely the SRS light stays on after the car is started, which may confirm my loose connection thoughts.
I'll keep looking, but this is starting to drive me crazy....
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Dear Volvo Mystery Sleuth,
Hope you're well. You just delivered the key clue: tapping on the driver's side airbag causes the SRS light to go out.
The ground fault is at the steering wheel, where the driver's airbag is housed, not the passenger-side airbag. I suspect that a contact is simply corroded. A film of corrosion invisible to the unaided eye can produce the problem you describe. A few passes with fine steel wool - or a spray of an aerosol corrosion-remover - should solve the problem.
Before doing any work on the SRS system, be sure to disconnect the negative battery cable's terminal from the battery's negative post. Put the negative battery cable's terminal into a plastic bag. Wait 30 minutes, for any SRS system capacitors to discharge.
You will need a long T-20 bit to reach the two screws, that secure the airbag to the housing in the steering wheel. You will need to turn the steering wheel, to access the screwheads.
Once you've loosened the airbag, You'll see a small, two-pin wiring connector, that goes into the airbag. Remove that, and set aside the airbag. Do not try to disassemble the airbag: there's no need to do so. The airbag itself is NOT the problem.
At the center of the airbag's housing in the steering wheel, you'll see the contact reel, the device that connects the airbag to the SRS system. One of the contact reel's connectors goes to the aribag. The other connects to the SRS wiring harness. Both of the contact reel's wiring connectors are a bright orange.
There should be no reason to remove the contact reel. See the warning label on a plastic strip attached to the contact reel. There should be a ground wire, for the contact reel. That's likely the source of the problem. Clean the contact and the underside of the screw head.
You'll also see several back wires, that connect the horn buttons to the rest of the car. ignore them.
Reconnect the airbag to its wiring connector. Secure the airbag by replacing the two T-20 screws.
Replace the negative battery cable clamp onto the battery's negative post. When you go to turn the ignition key to "start", do so at arm' llength from the passenger side of the cabin. This is a likely unnecessary precaution.
Volvo airbag systems have stood the test fo time. Occasional posts show that even after 20+ years, the Electrolux airbags work as engineered.
Hope this helps.
Yours faithfully,
Spook
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Yes, based on what you're saying, I'd be very suspicious of the aforementioned ground screw on the passenger airbag module.
Let me begin with the usual SRS cautions and a disclaimer. Before playing with any airbag wiring Please DISCONNECT THE BATTERY negative terminal to make sure the SRS control module (uner the driver seat) is disabled. Wait a few minutes (like maybe 20+ just to be safe) to make sure the internal capacitors are adequately discharged. NEVER USE A CONTINUITY TESTER OR OHMMETER ON ANY CONNECTOR TO AN AIRBAG, stray voltage and even static discharge can, in theory, trigger an airbag deployment. No matter what, always keep your head out of the bag deployment zone. Work around SRS systems presents added risks of serious injury and requires a certain level of competence and confidence. If at all in doubt, leave it to someone more qualified. Any work you do is done completely at your own risk, not anyone associated with brickboard.com, and most especially not me.
You shouldn't need to open up any of the SRS connectors, in fact this could be a very easy fix. With the glovebox removed, just carefully look under the airbag. You're looking for a long ground screw on the airbag module mounting assembly. It just threads through the frame and the tip touches up against metal. As I recall, there are no wires to it and it's in the very middle of the assembly. Once you find that screw, just back it off a few turns and then tighten it back in snugly. That should fix it. If you see any hint of corrosion then be sure to clean it up first, ideally protecting it with a little dielectric grease or DeoxIT paste.
Now, if I'm right, this deserves a double Thumbs Up as this is one rare occurrence and you just happened to say the right words to trigger a very old memory.
Let me explain that I only know this by virtue of once having had an airbag replaced by a dealer related body shop that I quickly learned to distrust. A couple of weeks later, the SRS light started coming on, much like with you. The OBD code led me to the passenger airbag wiring. I quickly determined that ground screw wasn't even finger tight. A few good turns of the screw quickly fixed the problem. That was 15 years ago, no problems since and I've never heard of it with anyone else.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Dear Volvo Mystery Sleuth,
Hope you're well. There's a faulty connection between the instrument cluster's battery indicator lamp, and a terminal on the alternator.
When this connection is faulty - usually because of corrosion on the connectors or a micro-crack in soldered connections - the alternator does not get the small flow of power from the lamp, required to initiate charging. That explains why, sometimes, the alternator does not charge. Your thumping the dashboard seems to suffice to restore the connection, so I'd guess the problem may be corrosion related. It could also be as simple as a loose connection.
The temperature gauge's failure also suggests a loose or corroded connection.
Be advise that a layer of corrosion, only a few molecules thick and so invisible to the unaided eye, suffices to prevent the flow of power.
You can remove corrosion by using an aerosol, such as DeOxit. This product should be available on-line.
Equally, a micro-crack in solder - which also cannot be seen by an unaided eye - can prevent the flow of power. These micro-cracks can be closed-up by touching to any suspect joint, the tip of a soldering iron (not more than 25 watts). A heavy duty soldering iron (e.g., 45 watts or more) should not be used. The excess heat will damage the blue-green plastic circuit card.
With a low-power soldering iron, only a one-to-two-second contact is needed. As soon as the solder turns from dull gray to shiny silver, remove the iron: the micro-crack has closed.
Inspect the thin red wire that connects the instrument cluster's battery warning indicator light to the alternator. If the wire is frayed, etc., replace it.
See the site's FAQs for instructions as to: (a) removing the instrument cluster; (b) re-flowing solder joints.
There should be no need to remove or otherwise work on the airbag.
Hope this helps.
Yours faithfully,
Spook
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Spook,
Thanks for the info! I will check everything next weekend and let you know how it turned out.
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