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[ELECTRICAL] What is this and why was it wired like this?
Hello,
I just recently purchased my first 1993 Base FD.
Been going through the car fixIing some stuff and came across this pictured below.
A previous owner (there were several before me) apparently cut the wire on what looks like a relay and wired directly from it to a red wire to a blue connector underneath the steering column inside the car.
Been going through the service manual and dont see any info on this or schematics.
Any Idea what this is and why they cut and wired it like this?
I think that's a headlight relay. Could have been some part of that system burnt out and they bypassed it.
Unplug the relay and turn the headlights on, if it's the relay in question they shouldn't turn on. The retractor relay that runs the headlights up and down is separate, I think it's in the relay box in the front of the car.
That blue connector is the harness going to the headlight switch and wiper stalk, I believe.
Figured id confirm what DaleClark stated for anyone that comes across this thread.
It was indeed the Headlight relay. Im in the process of going over my Emissions/engine harness and power harness as the previous owner/shop I bought the car from did a hack job with stuff.
Did some more digging around with this. So I finally reconnected the W/L wire of that relay. When I did that and reconnected the battery, the headlights would pop up and the headlights turned on. This must be the reason why the previous person ghetto rigged that wire to bypass something. I tried looking for a opening in that wire that maybe making connection with another wire and came up empty handed. The wire it self seemed to be fine. Looked at the FSM wiring diagram again and noticed that W/L wire from the headlight relay split off into the CPU2 or you could say that the CPU2 tapped into the W/L wire. Well this time I unpinned the W/L wire from CPU2 connector plug since the W/L already directly went to the combination switch harness. reconnected the battery and nothing happened, headlights didnt pop up and turn on. I used the combination switch to turn on the lights and everything works just fine and I pressed the pop up headlight button and it works like it should. So I am thinking that something within CPU2 is causing the headlights to turn on and go up. For now I have the W/L unpinned from the CPU2 connector plug. Will do some more research on CPU2 to see if there is maybe a diode or resistor or capacitor or something that can be changed out on it.
reconnected the combination switch wire that was cut
reconnected the W/L Wire on the headlight relay that was cut
Headlight relay
unpinned the W/L wire from CPU2 that taps in to the W/L going from relay to combination switch
A side note, I was wondering why my Cruise Control wouldnt work but never looked into it. well by accident when screwing around the the headlight relay W/L wire, I noticed some wires were cut and mangled up near the back opening of the driver side wheel well. Looked at it more and looked at the FSM wiring diagram and turns out its for the Cruise Control. Hopefully when I reconnect all that, it might work and not give me more issues after....
Another side note for the fun of it, Got my BBS Spirt R look alike wheels on. Havent worked on the suspension yet, but will when I get done with this wiring stuff.
will update again when I figure out the CPU2, unless someone already knows and can share their input.
Don't forget to check out the Body Electrical Troubleshooting manual (BEM). It has some troubleshooting steps for headlights that do not pop up. Do check CPU#2 for any leaked capacitors. If you don't see anything, there could be a problem with the main logic chip in CPU#2. Let us know what you find! I dig your rims too. They look sweet!
Thanks George, will for sure check out that section. Thanks for the heads up on what to look for inside the CPU2. If anything when I get time and dont see anything ill post pics of the inside of the CPU2 for better trained eyes to get a look at.
Alright here are pictures of the CPU2. I just took it apart and took pictures, didnt do anything else. Only thing I can possible think of would be the 220uf 16V capacitor at the top right on the bigger board which looks slightly bulged at top and bottom?
Get a close-in pic of the swollen cap. I'd say that is the culprit. Replace it and your cpu#2 gremlin should disappear.
I would also use a little distilled water and baking soda around that cap to neutralize any potential electrolyte leaks. Do not soak the board. Use a qtip around the localized area. Make sure the board is completely dry before reinstallation.
The smaller board is the flasher cpu and should not be affected by your problem. I'll inspect the photos later today when at my computer. I'm responding via GT app so excuse any mispelled words.
Thanks George, Ill let you look at the pictures first when your able to before I go buying parts. I took a lot of close ups of that one Cap. The Capacitor that I was referring to, to me it doesnt look that bad, doesnt look that puffy, but just slightly, not sure if they are supposed to be like that or not. I know you can measure capacitors, but I dont know a whole lot about doing it.
Ill take a look at the Body Electrical Troubleshooting manual in the meantime as you suggested before.
I finally sat down and reviewed the photos. For certain, the one cap with bulging top is bad and leaked electrolyte onto the board. In the next few photos, you will see red and yellow boxes/circles that denote specific things. Here is what they mean:
Red box = replace that component. Basically, replace the capacitors within this section. The one for certain is bad. However, replace the others as a preventative measure because they WILL leak in the future. Do make sure that replacements are available before ordering. Like the speedo board capacitor replacement, make sure you replace the capacitors with the exact same values in capacitance and voltage.
Orange box = High degree of damage to the legs of the component. I believe it's a transistor. Follow the cleaning procedures outlined in the yellow box and inspect. Consider finding a replacement for this component.
Yellow box/circles = spot clean these areas with distilled water and baking soda. Use a tooth brush and/or cotton swab as stated before to clean the localized areas. This would be the same as cleaning your car battery so expect to see some foaming action. That is the baking soda reacting to the acid. Do NOT soak the board or let the water stand. Let it drain off the board. Dry the affected areas with a hair dryer. Slowly move it around to avoid hot/burn spots. I doubt the hair dryer would cause damage but let's not risk it. Once dried, use isopropyl alcohol to clean up the solder joints. Inspect each joint for any damage. The component may not need to be replaced but the solder may need replacement. This will ensure a positive physical bond and a clean electrical bond.
Additionally, there are some components in these yellow boxes/circles that may have damaged leads from the electrolyte. This mostly affects some transistors (TR's/Q's) that are adjacent to the leaked capacitor(s). Be aware that these may need to be replaced. Pay particular attention to these transistors after you clean them. Once cleaned and inspected, then order all the components you feel are necessary to replace.
I'll post some additional notes in the photo captions. How does the back side of the board look? Could you take a few photos of it in this affected area?
Cheers,
George
Clean & inspect these areas. The tall black capacitor top is clearly bulged.
Clean & inspect these areas in yellow. Replace the 2 capacitors in red. The black one is certainly bad! Replace the brown one as a preventative measure.
Different angle, replace the capacitors in red, clean and inspect the yellow circle. Pay special attention to the transistor within the orange box. Clean and inspect it. I expect to see a missing leg on this transistor after it is cleaned. It has a high degree of replacement.
Good angle that shows more affected areas to clean and inspect in yellow. Replace the 2 capacitors in red, there is a 3rd capacitor (in yellow) that should also be replaced.
See the greenish corrosion in the yellow box? Clean and inspect!
Clean and inspect the yellow boxes. This angle shows all 3 capacitors to replace in the red boxes. Note hoe the tall black cap has a bulged top? That is a bad sign!
Yet again, yellow circles indicate clean & inspection points. Red boxes indicate the same caps to replace.
Top down view showing other components that require a clean and inspection.
Thanks for the input, will clean and replace the two capacitors with the correct ones and not make the same mistake like I first attempted with my Odometer (hehe) and see what transistor that one possibly damage is and find a replacement first.
Will get images of the back side of the board for you. Its amazing how out far out the capacitors leaked on the board, figured it would be right where the caps are, thats why i didnt think much of the caps.
No worries! Glad to lend a hand. Keep in mind the orientation of the body cpu when mounted in the car. It sits vertically so when the capacitors leak out then gravity takes hold. The good news is that the main cpu (marked as MPU) looks untouched. If that gets damaged then I would recommend replacing the entire board because that chip is no longer available.
Since you are replacing the one cap then you might as well replace the other surrounding caps. Now that you know what to look for then you may want to inspect the rest of the board for other potential capacitor leaks. Be sure to mind the polarity stripe that denotes the Negative lead.
Sorry to hear that your repair was unsuccessful. At least the replacement CPU#2 solved your problem. Thanks for the link! I wasn't sure if these Body CPUs were still available. I also wonder if Ray could beat that price?
For the most part, the backside of the board looks ok. There maybe some shadowing effect on some solder joints that cause them to look dull and grey. Solder that looks dull & grey may indicate a bad (cold) solder joint. They could be replaced with fresh solder.
Thanks for the input Alchemyst6. I figured if this cant be fixed first then ill order a new one. I like to go the least expensive route first majority of the time. Ive been ordering the mass of my parts from here https://www.mazdapartworld.com/oem-p...ule-fd0167560b
Looks to be the same price as that in the link you provided.
I'll have to check them out for future purchases. I've attached my order from from digikey that has part numbers for all the board capacitors if you need a place to start. I would recommend replacing that transistor at Q12 (outlined in orange)
also. I suspect that is where the problem lies with my old board. Eventually I will compare the circuits side by side to see if I can find the failure point(s).
08-26-17, 05:43 PM
