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Brake/battery light issue

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dgdsm

10+ Year Contributor
173
4
Aug 24, 2008
Tarzana, California
So it looks like I have some variation on the infamous Brake + Battery Light problem. I think I may have had it for a while, but only noticing it now, as it goes away on normal driving. A few details:

It usually happens on cold start, occasionally on warm start. If I rev the engine to 1500+ for 1-2 secs after cold start, it goes away. If I go into first gear and drive it these lights go off. Not if I go into reverse though. When these lights are on at idle, the battery is at about 12.3V: definitely not charging. After revving the engine for just a sec or two, it’s usually at 13.5V+ . The P/O told me he had installed a new alternator . It seems like it shouldn’t be going bad in under 2K miles, unless there was something else. It also might be related to idle. Some days, my idle is as low as 650 which is when I tend to see this. On other days, it’s at about 900 and I don’t see these lights on start as much or at all.

Time to shop for a new alternator? There are some threads about the cause being elsewhere. It could be the first signs of a voltage regulator on the blink, as I have seen erratic voltages at the battery in the past. The belts are a bit loose. The P/O had an elaborate sound system which he took out, leaving a lot of loose wires here and there, esp behind the radio. Wires could be moving around and creating intermittent drains or shorts. I know of a used dsm alternator not too far from my area for not a lot of $, but I don’t want to be going through alternators if the problem is actually somewhere else.
 
I'd start with capping off all the excess wires that the P/O had before anything. Verify there's no power wires coming from the battery and anything that can contact metal behind the radio. Also, take a look at the large 100 amp and 60 amp fuses in the under-hood fuse box-particularly the wiring under it to make sure there is no melting or major deformation.

Clean and re-seat the alternator/regulator plug (in front) and verify there's no frayed or shorting wires their. The dielectric sometimes cracks in that area right at the plug.

Finally, start looking into an alternator because you actually do have a tell-tale sign of the unit going bad. I went through exactly what you went through and it was in-fact the alternator (most probably the circuit inside). If you buy a used one, make sure to get it tested for free at a local parts-store. Try to find a good used OEM one because the parts store ones are hit or miss on the quality of the regulator circuit.
 
Re-tighten the alt belt first and examine belt for wear. Examine harmonic balancer (crank pulley) for separation signs. When they start to separate the belt is loose at startup and idle (but can tighten up at rpm). Test alt yourself - auto stores have a near worthless test (http://www.dsmtuners.com/threads/car-died-on-freeway-electrical-problems.258035/#post-151165661). So called new alts are usually rebuilt and auto stores have a terrible record of selling bad "new" alts.
 
I'd start with capping off all the excess wires that the P/O had before anything. Verify there's no power wires coming from the battery and anything that can contact metal behind the radiot.

The way it was sold to me was that there was in fact a power wire going directly from the battery into the radio. Actually the way it's set up is that it's fused into a wire (yellow color) that's supposed to come from the ignition switch. That is, if I go into the car and hit the power switch on the head unit without doing anything with the ignition switch, it goes on. There was one day that that power wire burned up from making contact with the metal wall on the passenger side. I replaced that wire in the same way it was configured before.

I'll try and get a decent picture. The right front speaker doesn't work.
 
Re-tighten the alt belt first and examine belt for wear. Examine harmonic balancer (crank pulley) for separation signs. When they start to separate the belt is loose at startup and idle (but can tighten up at rpm).

When I had all the belts and pulleys off last time, I wasn't too sure about the condition of the crank pulley. There may be some very small dents and imperfections. But I always thought that this was one piece of metal.

There is a slight wobble at the outer waterpump pulley. I don't have a good way to torque those bolts and tightened them by feel. There might also be a tiny wobble at the crank pulley, though not near as much as the waterpump pulley. The others (A/C and P/S) are spinning straight with no wobble at all.

I did tighten up that belt, so any remaining cold start belt squeal ---> all gone. But it didn't change anything on the Battery/Brake light problem.
 
Last edited:
Ok I think this may be a case of a DSM mystery problem with multiple causes.

It got worse quickly over the weekend, with the Battery/brake lights going on/off at times while driving. A part of the problem must have been a bad battery .. one of the cells was almost empty and I suspect it was leaking. Although the Battery/brake lights never stayed on continuously, I guess the battery wasn't getting charged, and it died yesterday (no-start). So I ended up making a AAA call and getting a $150 battery. 3-yr warranty so that's good.

I disconnected the audio after the no-start. Here is some of the loose wiring behind the radio. After that power wire burned up one day, I decided to learn more about automotive sound systems, and set up this terminal block to sort out some of the wiring mess. The power wire comes into the block at the connection marked by the arrow. I'll probably leave the audio disconnected until this problem is resolved. Some part of the problem must be loose wiring as the blinking Battery/brake light was happening especially when going over bumps in the road.

But the alternator part of the problem must still be there... it's back to Battery/brake light on at startup, and then going away after a few feet of driving. I did pick up this used alternator, and it is OEM (MD327513).

Thanks in advance for any advice / suggestions.
 
It's fixed. They tested the OEM alternator at Autozone and it passes on their machine.
It's putting out 14+V at cold start/ idle and there's no Battery/ Brake light. The
alternator I pulled was putting out 12.3V at cold start before I pulled it. There's a faded
label on it "1000 Performance Tested and Inspected" ... no clue who the supplier was. Maybe I'll take it by Autozone, or just trash it.

A few things:

(a) No problems at the 100A and 60A fuses; But when I checked for shorts (no ignition key),
it appears I have a drain in the "Room Lamp" circuit. This wasn't the source of the charging
problem.

(b) When I pulled the old alternator, there was a leak where the water pump meets the water
inlet pipe. The leak is probably at that joint, although I don't know that it's not the
water pump. It might be something intermittent ... I haven't seen it after I put it back
together and drove it. It's not a part of the charging problem, except: The leak point
is right on top of the alternator. It seems like any shaking of the engine from the old
mounts could drip some coolant on there.

(c) Looks like I have no cruise control system, which I've been wondering about. Someone
pulled it out. Don't know if that affects the electrical circuits, or not.

Thanks, evoredy and luv2rallye .
 
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