Parker 7, I am in no real rush so Please see what you can find. I will gladly pay for the resistors and mailing to FL

Thanks
Dan

 

Free

Researching

 

My airbags were fired off and not replaced by the previous owner before I bought the car

I have replacement airbags and before I hook them up will insure the module is not still in firing state

So when your replacement module is received you can do the same assuring that the received module is not in firing state

Send me a PM with your address

 

Small 5W resistors will be ok, thats what I used. The module looks for resistance between 0.7-4 Ohms. That way it knows if the airbags are actually connected. If the airbag or clockspring in the steering column went open circuit, the module would deactivate the system and show the airbag warning.

Dan: Since you have a physically burned module, you may have a shorting fault of some kind. You can at least do some tests without a module. You can disconnect the airbags, put the resistors in the sockets and look for 2.5 ohms on the module plug pins. That would insure connectivity through the clockspring at the module. You can test the crash sensors and safing sensors in a similar way, looking for continuity or ground as appropriate (and without any resistors). All of the necessary info about the wire colors and pin locations is in the Dummies guide. Just takes some studying to logicize it all. DO NOT try to measure the airbag resistance using the multi-meter. That could set it off in an uncontrolled explosion!

Parker: if your airbags were fired off before, you will need a new module! It is only good for one actuation of the airbags. When you get a new module, be sure to open it and test for continuity on the tabs of the thermal fuse box. Labeled F1. Outer tabs = thermal fuse, continuity (very low resistance); inner tabs = 15 ohm resistor. I believe the thermal fuse is designed to be a weak point in the system, as it is a catch-all for shorting faults that could cause burning (like yours Dan), especially after an impact.

 

Have asked this in the X305 forum, so apologies for anyone who reads this twice.

I went through the tests in the airbags for dummies document, and the voltage feed to the safing sensor, and the return from the safing sensor, was reading zero volts. All other tests passed (including the other safing sensor voltage tests, all about 25% of the battery voltage). Any tips on what it could be?

Only other thing of note was that the crash sensor voltages were all the same, and all constantly about a volt lower than the battery voltage.

 

Thanks , I have to remove a glove box surround panel ( with my color as I found one ) as a replacement off of a salvage X300 and will have to confirm or reselect a different salvage X300 for a non - fired module

So that means I can remove , open up , and play with the original module

Fortunately, the yard I use has about 4 X300s in different body states

 

I used Brendan's "Air bag diagnostics for dummies" and was extremely happy to be able to get the problem sorted out.
For Australian members JAYCAR carries 2.5 ohm resistors

 

My 1995 VPS has the common airbag light...followed the "dummies" diagnostice and could not get voltage on either RH and LH crash sensors when backprobing the plug at the module. I was getting .330 volts on both. I pulled the module and have the burned up thermal fuse and looks to be some burn damage to the board. See pics.
My questions are:
1. Will the damaged board casue no (low) voltage readings for the crash sensors?
2. If I replace the module will it immediatly burn up like this one?
3. If so, How do I fix the crash sensors to get voltage?

This car has never been in a crash - snesors look undamaged.

 

Answer to question 2 : yes expect it to burn the fuse again until issue resolved , commonly assumed every thing's fine from others experience

The thermo fuse was found as a known part # on E - bay / Amazon and such , looking

Thinking as I warm up to airbag knowledge base

Brendan is your man as he works in the airbag industry fortunately and should eventually see your post

 

I removed the RH crash sensor to bench test. It appears to be dead. Potted and no way to repair. Anyone have any idea how to test this thing with a multi meter? I get 0.2 ohm across the yellow and orange wires and open circuits on the rest.

 

On the face of it your readings sound about right.

I would suggest first testing the sensors at the Air Bag module rather than removing them. That way you are testing the wiring to and from them also. Put them back where they should be, unplug the connectors from the Air Bag module and test the circuits based on the wiring diagram and pin out diagrams that are included in the Dummies book.

So for example, on the RH sensor, put a 12v supply into pin AB1-11, and check that voltage comes back on AB1-2. I suggest doing load tests to confirm this rather than just measuring volts on a multimeter which can mask high resistance circuits.

The Sensor is grounded through its casing. So when bolted in place check you have good ground on AB2-8. If these tests pass the sensor should be good.


Repeat the tests for LH sensor.


It's possible you may have already fixed a common issue (lost ground through casing screw) by removing and refitting. That's why normally you would try the tests first from the module and then only disturb sensors when you have identified an issue and can prove it's fixed.


BTW @Parker 7 I have never worked in the Air Bag industry, just an enthusiastic amateur like most of us on here.

 

thanks for the advice. I mounted the RH sensor that I removed to a good ground location to run your test, because it’s hard to access the original spot. I was able to get 12v voltage back and verified good grounds on the pins you provided. Also verified good ground and voltage on the LH sensor. So I guess the sensors are good and the module is bad. I replaced the thermal fuse on the module, but still only getting .3 or .4v during the back probe test in your manual.

I found a used module on eBay, will have it here next week. With the data I have verified and provided here, do you think I will fry the new module if I just plug it in and test?

 

I would also carry out similar tests on the Safing Sensor at the module following the wiring diagram. Assuming you have already verified the integrity of the air bag circuits (that's standard tests in the dummies book) that's as much as you can do really and you should be good to go.

Note when testing the Safing Sensor circuit at the module with the connector unplugged you will need to remove or disable the shorting bar in the connector to test circuit for Pin AB2-6.

Just a reminder that all these test are with the actual Air Bags removed from the car!

 

yes airbags circuits are good; and airbags are removed and resistors in place. I’ll keep testing while waiting on the module.

 

I have nowhere near the level of knowledge that Brendan does on the airbags but from what I have gathered from reading others a common thing is the blown thermo fuse that accures when hooking things back together thinking things would be fine but.........................

If the airbags were blown on the salvage donor car I would expect the thermo fuse to be blown on the arriving module

I had the fuse # some time back

As Branden pointed out check for voltage before hooking up airbags as they will blow , I was lucky to have a local ( airbag shipping restrictions as explosives ) salvage yard with replacement airbags as mine were blown when I purchased M'Lady Penelope

 

That is waht I am worried about...blowing the replacement module when i hook it up. I received the replacement...nothing is damaged and fuse looks good! it's 2-3 years newer than my original and I see some differences on the baord. Major components are the same, but different lay out.

original from my 1995 VDP on top, after I have replced the thermal fuse.

my original...i did replace the thermal fuse here...but notice the black discoloration in middel of the board. I beleive this is more damage.


new board from a 1997 VDP

seller left connectors on module, so i will verify wire colors match.

 

No more Air BAG WARNINGS...replacement board worked.