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A9L Repair

29K views 123 replies 26 participants last post by  eycchu 
#1 ·
So my 88 A9L MAF conversion GT vert that I gave to my son started running bad at idle and lower rpm but ran good WOT. Since I wired up a CEL in the conversion, we ground the correct test pin and the light flashed Code 66, bad MAF signal. No problem, we put a new sensor in it less than a year ago so we swapped for a replacement. Same thing. I knew the wiring was good because it ran fine for a couple of years after the swap. So, we pull EEC and disassemble for a look. At first glance, didn't see an issue, so I get out the magnifying glasses and I notice discoloration under an electrolytic capacitor. When I give the can a little push, I can see one lead has corroded away. Since these computers now go for $150-$250, I decide to get capacitors. Solder them in and now things are back to normal. Below is a pic of the board showing where the 3 electrolytics are located and their ratings. I had to buy 10 sets of repair capacitors as that is the smallest amount I could find online. Since only the one was failed, that one is associated with the MAF processing circuit. Thought you guys might like to see this info. If anybody wants one of the 9 repair sets (3 capacitors) I have left, $5 shipped to your mailbox. PM me for my address.

 
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#2 ·
Good job repairing.

When you or anyone runs out of parts, any reasonable voltage greater than original can be used (say up to 3 times). Capacitance can be at least doubled without issue. Most of the time capacitance can be several times original.

The function of those parts is to bypass noise to ground, so more capacitance generally does not hurt as long as the part fits. The real issue is lead size and spacing to fit holes.

Hows that LS volvo?
 
#3 ·
Thank you for sharing. I'll save this info in case my A9P has a similar problem some day.
 
#6 ·
Did you replace the caps with the original aluminum liquid electrolyte type or did you find some polymer e-caps? I've noticed that all EEC-Vs only use polymer e-caps, probably making them many times more durable than EEC-IV with liquid electrolyte.
 
#8 ·
Sounds like I ought to grab a set myself! Thanks!
 
#12 ·
This was surprisingly easy with a solder puller. Total time was 2 hours. My capacitor for the MAF was shot and the neg lead was corroded and loose. Would explain my recently varying idle. Now it idles very deep and hits solid, not fluttering like before. Thank you.
 
#13 ·
So what parts is everyone using for their refurbish job? The newer EECs have those solid state caps that are supposed to last a lot longer... I believe they are electrolyte free.
 
#15 ·
Yes, but I'm referring to specific part numbers and manufacturers. You know, like TI DM3686 or something like that.
 
#16 ·
you can buy the newer design caps with the same ratings as the originals, you don/t need a part number. Search on Amazon with the cap ratings and they will come up. You have to buy multiple caps as they are only sold in small lots at decent discount pricing.
 
#17 ·
I was going to simply add the part numbers to my company's next order for parts. We have accounts with Mouser, Allied, Newark, Digikey, etc.
 
#20 ·
I had the exact same capacitor go bad on my X3Z. MAF voltage was all over the place. I was able to get single capacitors, 2 of the 47's and 1 of the 10's, from Mouser. They cost me more to ship them than what the capacitors cost. After installation of them my voltage is now as it should be.
 
#22 ·
Any style newer capacitor is more reliable than a 30-40 year old part. Just buy any properly sized and rated part from a name brand manufacturer like Panasonic or Nichicon.

Unless abused, they will be good long after the car is gone.

Go to Mouser or some reputable new component distributor. Don't buy components from Amazon. There are rejects and seconds that are sold off surplus, you do not want to accidentally buy a QC rejected part just to save a dollar.
 
#26 ·
Tmoss you still have any cap sets available??
 
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#31 ·
Here's exact replacement part #'s from Mouser.

Quantity 1:
647-UKA1C470MDD1TD
Nichicon Aluminum Electrolytic Capacitors - Leaded

Quantity 2:
75-511D106M063AA4D
Vishay Aluminum Electrolytic Capacitors - Leaded

Unfortunately on the ECC I just looked at for a friend, the traces/pads beneath the capacitors were completely ruined by the acid that leaked out of the caps.

I'd recommend anybody who is still running the EEC-IV and plans on it for a while, to replace these before they fail and not after. It's a simple task to replace them before they've ruined the board, it is not a simple task after.
 
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#32 ·
Looked into this a bit further and why not use the aluminum polymer solid electrolytic caps instead of the standard type of aluminum liquid electrolyte caps?

I think the following parts would probably fit the bill nicely and last a lot longer with zero possibility of leaking out and corroding a PCB.
10 uF part: Nichikon PLV1K100MCL1TD
47 uF part: Nichikon
RNS1C470MDS1


 
#33 ·
I don't know why not, which is why I don't mess with it :). There's more to a capacitor than voltage and farads, in a fact a whole mess of ratings and characteristics that an electrical engineer probably knows and understands but I haven't gotten around to that education yet (specifically ESR comes to mind which is different between the two, and depending on circuit design changing this can change voltage bias which is a bad thing for any voltage-sensed engine parameters).

What I do know is the different constructions are suited to different purposes. The common assumption is that electrolytic aluminum caps are only used because they are cheap, but they are actually the best for the job at some things. I don't understand well enough just how tailored these caps are to their purpose in these circuits to make the call to change the type.
 
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