Electrical: Replace ECU, ECS and Climate Control Capacitors

This article will teach you how to replace the ECU, ECS and digital climate control capacitors in a Mitsubishi 3000GT/GTO and Dodge Stealth. This maintenance is particularly useful if your stock capacitors have started to leak, which can be considered a fairly common occurrence for our cars as the years pass by. Leaky capacitors are most likely to be found on first generation 3S's (1991 through 1993), but are not unheard of for later years as our cars advance in age.

The good news is replacing these capacitors requires minimal tools and only the essential electrical knowledge to complete. The replacement capacitors are relatively inexpensive (less than a dollar each) and are fairly easy to find as well.

When shopping for replacement capacitors, make sure that they're rated for operating temperatures between -55°C to 105°C (-131°F to 221°F). Also be aware that many retailers offer longer life capacitors as well (2000-3000 hour), which may cost slightly more, but are completely acceptable to use if you wish.

Leaking ECU/ECM capacitor

Capacitor replacement toolkit

Where to Purchase Capacitors

Most of the capacitors used in this tutorial were purchased from DigiKey.com using the listed part numbers below. Alternatively, some community members have also had luck finding similar capacitors locally as well (e.g. at Radio Shack).

Signs of a Bad Capacitor

How do you know if your capacitors have met their maker? There's a good chance you'll smell it -- it's not pleasant... unless you like the smell of rotting fish. For the digital climate control, you may notice that your screen no longer functions. Terribly annoying reactions tend to happen when the capacitors in your ECU/ECM begin to leak; intermittent starting problems, car will run poorly/stutter, and may eventually completely shut down.

When in doubt, simply pull the unit in question, open it, and take a look around the circuit board. If you see yellowish gunk, or even if you want to preemptively strike an aging capacitor that might begin to leak, then you've come to the right place for help!

Tools Required

• Phillips screwdriver
• Flathead screwdriver
• Soldering toolkit
  • Solder w/ flux core
  • Soldering iron
  • Desoldering iron w/ integrated vacuum pump (or solder braid)

The image to the right shows the tools used for this guide.The desoldering braid wicker tape is the blue plastic circle thing with copper braid sticking out. The brown bottle is liquid flux (I initially used that to coat the wicker tape for easier sucking but I don't think it was necessary at all).

Replace Climate Control Capacitors on a Mitsubishi 3000GT/GTO and Dodge Stealth

Capacitors for Digital Climate Control

Qty	DigiKey PN	Product Information	Location(s)
1	P5528-ND	47uF 16V	C4
1	P5566-ND	4.7uF 50V	C5
1	P5570-ND	47uF 50V	C9
1	P5543-ND	470uF 25V	C10
2	P5134-ND	10uF 16V	C11, C17
2	P5541-ND	220uF 25V	C14, C15

Diodes for Digital Climate Control

Qty	DigiKey PN	Product Information	Location(s)
3	1N4004	1 Amp (Generic)	D5, D6, D7

Resistors for Digital Climate Control

Qty	DigiKey PN	Product Information	Location(s)
1	PPC1.0W-1CT-ND	1.0 Ohm 1.0 Watt	R38

Transistors for Digital Climate Control

Qty	RadioShack PN	Product Information	Location(s)
1	276-2027	65W TO-220 (TIP42G PNP)	Blue-green transistor on heat sink

Access and Open Digital Climate Control Unit

1. Remove center vents. Use two flat head screw drivers to lift up the hidden tabs inside the vent and a third flat head screw driver to pull the vent out. This will give you access to the top screw holding the automatic climate control display.
2. Remove radio and any trim that's in the way of the climate control display. The display has three screws holding it, I've circled it in red in the pictures below.

   

   Climate control unit screw locations

   

   Climate control unit upper screw

3. Remove digital climate control display from the dashboard. It's difficult to remove the display out without scratching it, so I suggest putting masking tape on it. I didn't have any tape so I cut the useless white plastic piece that's hidden behind the radio trim. This makes removal much easier. Before you can remove your display unit out, you'll have to disconnect two connectors at the back and also move the black plastic box below it -- this black box is held on with four screws. I believe this black box is the climate control brain.
4. Open the digital climate control by removing the 10 screws from rear of the unit. If your capacitors are indeed fried, you may begin to experience a burnt fishy smell.

   

   Climate control rear screws

5. Pull internal circuit board from the case and remove the rubbery buttons. The rubbery buttons will likely fall off on their own, but it'd be wise to remove them regardless so that they don't accidentally get burnt by your hot soldering iron.
6. Inspect the digital climate control's circuitry and display for visible damage. On the display itself, you may notice two burnt marks on the right (seen below). Don't be alarmed, apparently this is normal. On the circuitry, you will likely notice where the leaking occurred. In my case, capacitor C15 failed and leaked onto diodes D6 and D7, causing the writing on the diodes to burn off. Before continuing to the next step, take note of your capacitor's size, voltage rating and location. Also observe the capacitor's polarity as the new ones must be soldered in the same direction. Write all this stuff down, take photos if needed.

   

   Climate control unit VFD

   

   Failed c15 capacitor

Replace Digital Climate Control Capacitors

1. Desolder and remove the VFD (display). This particular task took me many hours and is easily the most difficult part of this project. I used the braid desolder method but would suggest using a better tool such as a desoldering iron with integrated vacuum pump to make the task faster/easier. If you can, try using an alligator clip on the leg of the VFD that you are desoldering to keep from heating up the display too much. Then, after desoldering as best you can, you'll need one hand to hold the circuit board, one hand to hold a soldering iron to all 3 pins of the one leg, one hand to gently apply pressure to the VFD away from the board, and one hand to pry the leg up at the same time. This is where you might want to call in a help of a friend.
2. Solder in new diodes (if needed). Using new 1N4004 1 amp generic diodes, I replaced diodes D6 and D7. Polarity matters, so be sure to solder them in the same direction as mine.

   

   Replace diodes as needed

3. Solder in new resisters (if needed). Some people have reported R38 to be burnt up and in need of replacing. If R38 is burnt and continues to get burnt after replacing it, some members have had luck replacing the blueish-green transistor bolted to the heat sink (refer to the table at the top for part numbers). I also took the time to upgrade R55 from a 8.2k resistor to a 12k, and R56 from 160 ohms to 750. Here's a photo of a bag of 1 watt resisters being held up next to R38 to illustrate that the original resistors are probably a bit smaller than 1 watt rating.

   

   Replace resistors as needed

4. Solder in new capacitors. If you have any residue build-up under or around your old leaky capacitors, it is highly recommended that you clean it up. This stuff is corrosive and will surely cause issues if unaddressed.
5. Re-solder your VCD back.
6. Reassemble, reinstall and test the repaired climate control unit. You're good to go!

Other than that, in case you have other damaged components, here's some pictures of my display unit circuit boards for you to compare with.

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Replace ECS Capacitors on a Mitsubishi 3000GT/GTO and Dodge Stealth

Capacitors for the ECS Unit

Qty	DigiKey PN	Product Information	Location(s)
2	P5570-ND	47uF 50V	C1, C5
3	P5528-ND	47uF 16V	C10, C23, C32
1	P5562-ND	0.47uF 50V	C16
13	P5563-ND	1uF 50V	C14, C17, C18, C19, C20, C24, C25, C26, C27, C28, C29, C30, C31

Access and Open ECS Unit

1. Access and remove ECS unit. Your ECS is located in the passenger side trunk area (assuming RHD vehicles), pretty close to the very rear of the car. It's held on by three screws. If you find that the screws are on unbelievably tight, you may need to remove the plastic trim panel pieces to gain good leverage.
2. Open the ECS unit casing. Pry open the tabs and separate the shell casing. Remove the two screws that separate the board from the casing.

   

   ECS unit with closed tabs

   

   ECS unit with open tabs

3. Inspect and take note of any visible damage inside the ECS unit. Note capacitor location, sizes, etc. Below is what my ECS looked like. Everything was still in good order with no damage. Take note of the 19 electrolyte capacitors polarity all face in the same direction.

   

   Virgin ECS unit circuit board

Replace ECS Unit Capacitors

1. Desolder capacitors. My technique for this task was to solder wick using a braid each capacitor before bringing it to a vice. Once the board was secured on a vice I took some needle nose pliers and wiggled the capacitors free while heating the ends. To help make this even easier, I grinded my soldering tip to a very sharp point so I could insert it deeper. You might want to print this picture so you know where the desoldering points are located. You can see some of the silkscreening on the front photo showing the original locations of the capacitors that were removed.

   

   ECS unit with capacitors removed (rear)

   

   ECS unit with capacitors removed (front)

2. Reassemble, reinstall and test the repaired ECS unit. You're good to go!

   

   Completed ECS unit with new capacitors

Replace ECU/ECM Capacitors on a Mitsubishi 3000GT/GTO and Dodge Stealth

Note: Another (more elaborate) version of this tutorial can be found here: How to Replace the ECU Capacitors in Your Mitsubishi 3000GT/GTO and Dodge Stealth

Capacitors for the ECU/ECM Unit

Qty	DigiKey PN	Product Information
1	P5568-ND	22uF 50V
1	P5570-ND	47uF 50V
1	P5540-ND	100uF 16V

Access and Open ECU

1. Disconnect negative terminal on your battery. This is an important first step when you're working with anything electrical on these cars.
2. Remove ECU. Your ECU is located behind your radio and is secured on by three bolts. You need to remove the side trims to gain access. Use a 10mm wrench to remove one bolt on the passenger side and the two bolts on the driver's side. Pull the ECU out and then disconnect the ECU harness. Be sure to unlock the ECU clips before pulling. I find it helps to use a flat head screw driver when pulling the connector. Don't pull on the wires as you may damage your harness!
3. Open ECU Case. If your ECU has never been open, those screws might be on there super tight. To avoid stripping the four black screws use a cordless drill and put a lot of weight behind it so the bit doesn't slip.

   

   Open the ECU Case

4. Unscrew the circuit board. In order to access the capacitors, you need to remove the cover and unscrew four more screws that hold the circuit board down. Remove these screws.
5. Inspect and take note of any visible damage of the circuit board. Write down the polarity of the capacitors so that you can install the new capacitors in the same way.

Replace ECU Capacitors

1. Desolder the stock ECU capacitors. To remove the capacitors, I would use the same technique mentioned above with the ECS capacitors. First suck the solder out, and then pull the capacitors out while heating the ends.
2. Solder in the new capacitors. I intentionally left mine long so it will make future removal easy. This is now my third set of capacitors for preventative maintenance.

   

   Install new capacitors in the ECU (top)

   

   Install new capacitors in the ECU (angled)

3. Reassemble, reinstall and test the repaired ECU unit. Reinstall screws, case lid, screws again and finally reinstall into car. Reconnect ground battery.