thepurpleblob

It's about a year old... I made it myself. I recycled the 14 pin connector and it looked in good condition. I'll go and check it if you think it might be relevant. It's a fair point - I'll re-check my work very carefully.

Yeh - a fuse wouldn't work if it didn't have some resistance. You get a small but measurable voltage drop (sorry - not amperage, my mistake) across the fuse pins with it in circuit.

thepurpleblob

I'm not sure why I didn't notice before - my car doesn't have an interior light relay (XXI). The space is empty. Is there any scenario in which the car doesn't have one or is it just plain missing?

(Possibly because somebody was having problems in the past)

SwayBar

I would be curious to know what the current draw is at the battery - have you measured that yet?

thepurpleblob

Yeh - it's in my original posting. It's about 50mA whenever I measure it. Although it does vary a bit. Which, of course, doesn't account for the problem.

thepurpleblob

Update - although no smoking gun... this is stuff I have done..

- taken it out for a good run, waiting a few minutes, no unusually warm relays. Waited more minutes, ditto.
- checked more carefully the current draw at the battery. On connection it's 60mA, after two or three seconds this drops to 10mA and stays there. It makes absolutely no difference when I do this (e.g. after it's been sitting or immediately after being run). Clearly not enough to account for the problem.
- I've checked the 14 pin connector carefully. All the soldering looks good and the connector (still) looks in good condition.

So I'm still completely clueless...

Mrmerlin

are the rear edge lights out in the doors when they are closed/
NOTE roll the windows down to see inside the doors to verify the lights working.
NOTE did you check that all the interior lamps are properly wired

thepurpleblob

NONE of the interior lights work on the door switches. The red lights in the doors don't work at all. The white lights on the door cards work in "manual" mode. As mentioned above, the "timer relay" for the interior lights is missing from the fuse/relay board (I don't know why - it came that way).

In any case, is that likely to (a) result in an intermittent issue that I've never seen and (b) kill a battery in a matter of a few hours.

EDIT:
I notice that the 1985 wiring diagram doesn't have the interior light relay but the 1986 diagram does. Possibly my 1986 car has the earlier wiring.

Kevin in Atlanta

I had a battery go flat in less than 5 hours. The only thing that was unusual was I left the windows down. I think the switch was stuck.

No repeats since that one occurrence.

Mrmerlin

a seat switch can also stick,
Make sure they are all centered,
good call on the sticking switch Kevin

thepurpleblob

What I can't understand is that I am consistently measuring the battery drain at 0.01A (10mA).

This afternoon, I took the car for a run, parked it up and measured the battery charge - 98%. I checked the drain (10 mA as usual). I then just left it connected. After approx 4 hours the battery had dropped to a 30% charge. Checked the drain (10mA still).

So, I'm really missing something or doing something properly stupid.

BTW... I've checked the battery drain with two different metres. Same result.

gazfish

How are you measuring the current? Have you taken one lead off the battery and put the meter in series so there’s no other route for the current to take? Is the battery lid up when you’re monitoring it so there’s no chance the lid is shorting the +ve?
Do you have a GoPro or similar you can use to watch the meter for a few hours to see if the draw is changing?

thepurpleblob

The lid is open and I have the earth lead disconnected from the battery. I've got the ammeter in series with the earth lead and battery. There's nowhere else for the amps to escape (I hope).

My wife has a GoPro... that's a thought.

FredR

Perhaps the Blob should calibrate the test kit with a known ampage draw just to make sure he is not being led up the garden path.
I use a nice DC clamp on meter to do such checks. For the last 20+ years I have been using a sheet of inner tube rubber to ensure isolation of the positive terminal from the lid . Most unlikely that would have been the problem-when this happens the inrush current is well over a 1000amps and the lid welds itself to the battery post -then you cannot open the lid and the battery is completely knackered.
Ask me how I know this! Fortunately my battery was only a couple of weeks old- told the shop the battery had failed and got a new one. Had they asked why it failed I would have told them the truth-see honesty really does pay!

thepurpleblob

Fair point about the meter. I've tried it with two different meters and got the same result but - clearly - it doesn't add up.

I think rather than moaning about it, I'm reduced to systematically disconnecting stuff and then monitoring the batter charge until - hopefully - I can narrow it down.

Mrmerlin

After all of the battery drains I would start with a fresh battery then redo the check I suggested to find a hot relay
make sure the window switches and the seat switches are all centered in the rockers I have had both stick to on the seat switches are harder to find cause they are out of sight
Also make sure the defrost switch is turned off it has a push on timed circuit and manual twist on