After spending two days tracing a parasitic power drain, I discovered that the right hand door lock solenoid/switch is causing an extra 40ma draw in the unlocked position which goes away in the locked position. I suspect one of the two charging electrolytic capacitors is failing, that one of the diodes is failing, or I’ve got corrosion causing the drain, since the drain only occurs in one position of the solenoid/switch.
Has anyone taken one of these apart to replace any of the electronic components? Any help would be appreciated.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
Electrolytic caps and diodes are cheap, and electrolytic caps are known to malfunction when old. Just replace them all while you’ve got the door panel off and be done with it. It’s a fairly safe bet the solenoid itself is OK.
And take pictures please. Heck, take some pix of the window motor while you’re there, as we could always use more info on those things.
And be sure to report if your 40ma draw goes away. Thanks!
Got the solenoid out. Electronics are under the rubber cover. Someone had already replaced one of the caps. I believe the blue was original, and the black was a replacement. Blue tested at zero capacitance and only a little over 1 ohm resistance. Black tested ok. Resistors and diodes in the circuit tested ok.
I’m ordering new capacitors, but I had a used cap in my stash of the right capacity that tested ok, so I soldered it in as a test. 40 ma excess draw went away, so the bad cap was obviously the problem.
I happened to have another blue cap in my stash identical to the one I replaced, but it tested bad as well. The blue caps are only rated to 85 degrees C, but the black ones are 105 degrees C. so the black ones should last longer in a hot environment. I believe the blue caps are original, as they fit the holder better than the black, but I can’t prove it.
Anyway, a successful repair. BTW, just roll the window all the way up, and push the vapor barrier out of the way to access the two bolts that hold the solenoid in place. I used a 1/4" drive with a long wobble extension to reach the bolts. Once the bolts are out, you can move the solenoid around, and undo the two electrical connectors, and the rod that attaches the solenoid to the door lock assembly.
A couple of further notes; the black plastic assembly that holds the capacitors, resistors, diodes and microswitches can be separated from the main body of the solenoid by removing two long screws that accept a flat blade shown in the end-on photo. There is no direct electrical connection from the plastic electrical assembly to the solenoid at all. The actuator rod on the solenoid has a plastic piece that actuates the microswitches. The resistors can been seen on the side of the black plastic piece when installed on the solenoid, but the diodes are on the bottom and can only be accessed and tested by removing the assembly from the solenoid.
I was able to isolate the issue to the door lock system initially by removing fuses and relays from the various locations until I found the one with the current draw. Then I isolated it to the passenger door by removing the outer kick panel and unplugging the connectors there that go between the body and door. On my 85, there were three of them. The color codes on those wires for the solenoid/switch do not match the ROM or the electrical diagnostic manual. The two connectors that affect the door lock system have orange wires on one, and several purple wires on the other. One interesting point was by disconnecting the connector with the purple wires, but leaving the orange wire connector connected, the solenoid in the passenger door still worked, and would lock and unlock from the driver’s door, but the passenger door wouldn’t unlock the driver’s door, either from the outside or inside.
Before I did this, my battery drain with all doors closed, everything turned off was 60ma. After fixing the issue, it dropped to around 19ma. The remaining draw is from the radio keep-alive, a remote add on to the lock system, and a tiny amount from the trip computer. I’ve found with various cars that any draw over about 30 ma after everything has settled down is probably too much and needs to be investigated. The 60ma I had was way too much, especially for a non-computer car like the XJS.
Got the new capacitors from Digikey, and installed them. Door locks work perfectly, and excess battery drain is gone. Kind of a fiddly job getting the solenoid in exactly the right position to ensure that the lock and unlock functions work correctly, but not hard.
Photo is of the part number for the capacitors I bought. 1000uf, 16v, 105c.
One thing I failed to mention is that the capacitors are polarized. Both the old and new ones have a clearly marked negative terminal. Be sure to match up the negative side when installing the new capacitors.
