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SRS Failure

Joined
15 December 2008
Messages
444
I recently had a most unusual failure that appears to be due to aging parts on our cars. Recently, I took my stock '91 NSX out for a drive and run some simple errands. After I completed one of my errands, I returned to the car, started it, the SRS light stayed on. I let the car idle down and then turned the car off and restarted it hoping it would reset the SRS computer. No such luck. I continued with the remainder of my tasks for the day and upon returning home, researched the matter here on Prime. Much of what I read was to check the fuses. Well, low & behold, fuse #1, the one with the yellow cover was blown. I promptly replaced it thinking my issues would be resolved. Unfortunately, it didn't resolve the matter, in fact after a few more blown fuses I realized that I had a serious problem.

I then began the painful process of checking for shorts and did indeed find that there was a short between power line of the SRS and ground. Since there had been no alteration of my cars wiring, I couldn't figure out what may have caused such a short. Also, the car (fortunately) has never been in a collision so the sensors couldn't have been damaged from any trauma. I also had a factory steering wheel and airbag so I didn't think they would be the issue.

While researching prime, I found a great write up on the removal of the SRS computer, so I decided that was the last component that I needed to evaluate. Initially, I didn't intend to remove the computer, rather simply remove the connector from the computer to see if the module may be the culprit in causing the short. Sure enough, if the SRS was removed, the fuse wouldn't blow; however, if the computer was connected, the fuse popped. Thus, I proceeded to remove the SRS module. The write up by Madbox was perfect. The one thing that I would emphasize is that the Torx bolts holding the unit to the body are coated with locktite and are pretty hard to remove.

After removing the computer, I decided to pop open the module and see what might be amok. To my amazement, it was the same issue that has riddled my CCU & amps...failed capacitors! You could visibly see the leakage from the capacitors. Since I am not that adept at the replacement of the capacitors, I went ahead and purchased an entire new module. One note was that unlike the original post by Madbox, my unit was not exposed to any moisture leaking from the A/C unit.

After receiving the new module, I installed the unit and everything operated as it should. I re-assembled the dash and went back to enjoying my beloved NSX.

I simply wanted to share this experience with others should they run into a similar problem. Seeing that this is a similar problem that is affecting our CCU's & Amps, I fear that we'll see more of such similar problems as our cars age.
 

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Thanks for the heads up NSX2K. So how much did a new or was it used module cost and where did you get it? Also why not just change capacitors? Perhaps have an electronics technician change them.
 
I went ahead and purchased new. It was around $800. My reluctance with a used unit was that I was concerned that those capacitors would also, in time, fail and I didn't want to go through the whole process again.

I didn't replace the capacitors myself because I wasn't adept at such procedures. Certainly, that would have been cheaper.
 
Thanks for the in depth info and for sharing your information with us. I know as our cars age we will all benefit from your research and conclusions.
I, myself, know if this situation comes up this will be my first avenue to pursue.

Perhaps Brian will add this repair to his list of services so we can all avoid the $800 purchase price of the new units.......... With his CCU repairs, I don't see why I wouldn't trust replacing these caps with new ones.
 
Thanks for the in depth info and for sharing your information with us. I know as our cars age we will all benefit from your research and conclusions.
I, myself, know if this situation comes up this will be my first avenue to pursue.

Perhaps Brian will add this repair to his list of services so we can all avoid the $800 purchase price of the new units.......... With his CCU repairs, I don't see why I wouldn't trust replacing these caps with new ones.

I have repaired one of these units and am now offering that service so if you are blowing fuses get in touch with me.
 
For the DIYers: what to take care of? I didn't play around with SRS systems so I don't want to blow it eventually.
 
I am experiencing the exact same problem in my '91. This is a dumb question, but how do you remove the #1 fuse (the one with the protective cover)? The little plastic extraction tool in the fuse box does not fit over it. I suspect that I might have the same problem with the SRS computer, but want to rule out the easy/inexpensive option first.
 
I am experiencing the exact same problem in my '91. This is a dumb question, but how do you remove the #1 fuse (the one with the protective cover)? The little plastic extraction tool in the fuse box does not fit over it. I suspect that I might have the same problem with the SRS computer, but want to rule out the easy/inexpensive option first.

Just pry off the yellow cover with a screwdriver and then take out the fuse.
 
I was starting to dismount the SRS control module today until I had to give up. The Torx screw holders broke both on the passanger side. Now the screws rotate but can't be removed, they have to be drilled. Obviously, the car was starting to get on my nuts...why did they torque these Torx like a dork?! I mean: Torx, 10 Nm, lock washer and Locktite???! Bloody car! The module doesn't explode like a nuclear bomb in a crash, does it? :rolleyes: I'm waiting until the car gets pissed itself (until the dash has to come out)...
 
The screws are held in with red Loctite. Attached is photo of what the factory replacement screws look like.
SRSScrews.JPG
 
I agree with goldNSX, the area is pretty tight and do run the risk of potentially burning something near by.
 
Those SRS screws suck. I broke 3 of the 4 as I recall. Had to use self tappers to get it setup again. Great to hear BrianK's heroism knows no bounds. Must have same primers over a $100k by now...
 
Those SRS screws suck. I broke 3 of the 4 as I recall. Had to use self tappers to get it setup again. Great to hear BrianK's heroism knows no bounds. Must have same primers over a $100k by now...

If you compare my prices to the cost of new parts and the # of repairs I have done over the last 10 years its over a Million in savings to NSX owners.
 
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I finally got the unit out. Well, no leakages after 22 years but I'll change the caps for sure.

Not sure about the orange one in the picture above, it's a 3900/35V and it's very fat for this kind of values. The top of it is coated in plastic. Anyone with more info in it?

Brian, do you change the orange one too?
 
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I finally got the unit out. Well, no leakages after 22 years but I'll change the caps for sure.

Not sure about the orange one in the picture above, it's a 3900/35V and it's very fat for this kind of values. The top of it is coated in plastic. Anyone with more info in it?

Brian, do you change the orange one too?

No, are you blowing fuses?
 
No, are you blowing fuses?
No blowing fuses.
I can't find a direct substitute for the big orange one. The contact spacing is 22.5 mm. The max height the case allows is 40 mm.
 
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No blowing fuses.
I can't find a direct substitute for the big orange one. The contact spacing is 22.5 mm. The max height the case allows is 40 mm.

I don't see any need to replace the big orange one the only ones that have leaked were the 330 X 35V ones so if you don't have any leakage just replace those 2.
 
I don't see any need to replace the big orange one the only ones that have leaked were the 330 X 35V ones so if you don't have any leakage just replace those 2.
Thanks very much, Brian.

My friend (a lawyer) came up a thought why the screws on the passanger side break 'by design'. Honda likes to see if there has been any work on the SRS unit, if yes, they have a chance refuse liability if anything goes wrong with the airbag. If they can't proove you in court they're in trouble. It's a very high effort to put it back in a state you don't see anything at all which heads to my next problem:

Should I drill the screw completely out? I thought it can be removed completely while cutting the head of the screw off which is not. Or drill a different hole to attach the unit? What did people do?

EDIT: I've put the SRS unit in the car today, It still works, lucky me. I've drilled holes on the passanger side and used a scew/nut-combo.

I've read about water in the unit and about drilling holes in the underbody. I think this is second best. As I don't want to have ANY water in the unit I've taped it on the sides esp. on the plug side because it's there where water COULD enter. Even with a bucket of water from above I won't have water in the unit.

I'm waiting for the caps to arrive to complete the radio head unit...
 
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