mcgrizzler

Hi Everybody,

I just picked up a 1995 LS400 last night off Craigslist, it's in pretty decent shape, but it definitely needs some TLC.

The person I bought the car from stated that it had a check engine light on and that occasionally the speedometer would stop working while driving. I scanned the car and got code P1600 "Battery Malfunction" and had read up a bit before purchasing the car and figured the speedometer issue might have something to do with bad capacitors in the ECM.

After picking up the car, it also stalled twice while idling in drive.

Today I pulled the ECM out and sure enough, at least two of the capacitors have leaked some brown stuff onto the board. I have all 6 of them on order from Mouser they should get here on Monday.



While I'm waiting on the capacitors to arrive, I decided to clean up the car. This is where I ran into an issue that I'm not exactly sure how to form a correct search term for, and don't know if its somehow related to the ECM. All of the electric motors in the car, like the mirror adjustments, seat adjustments, steering wheel, and windows seem to work fine until you try to actuate the motor around 5 times in a row. They then suddenly start to get sluggish and just stop all together.

For example if you were to roll down the driver side window, it would roll up and down about 3-4 times, then start to rise very slowly and then just stop all together.

Turning taking the key out of the ignition and letting the car sit for about 10 minutes seems to reset the issue and allow the motor to work again, I should note that when one motor stops working, all the other ones will still work 3-4 times before stopping themselves.

Sorry if this has been asked before I just am not too sure how to word what to search for something like this or if the ECM caps have something to do with this. Any point in the right direction is greatly appreciated.

Glad to be on the forums and excited to get this LS up and running!

oldskewel

iTrader: (1)

Does it do the same thing when hooked up to a battery charger? If no, then it sounds like a weak battery.

mcgrizzler

Unfortunately I don't have a battery charger available to me, however I could pick one up tomorrow and try.

I did forget to note in my post though that the battery in the car was purchased a few days ago (I have the receipt) and metering it shows 13.1v when the car is off, 14v when the car is idling.

Also, the motors act the same regardless of if the car is running or off. (I have the ECU plugged in so I can roll it around for street sweeping while I wait on the capacitors)

jaaa

The motors in these cars are just getting old. Especially the ones that move the steering wheel up/down in/out, because they get used twice each time the car is started. Lots of times, these motors will work fine if cold, but if they get into high heat conditions they will slow down and then stop. As you use these motors, they heat up internally and the same thing happens. When you let them rest awhile, they will begin to work again.

YODAONE

Remove door panel an lubricate window motor and lift mechanisms.

The window rollers are probably tired......

JohnAndic

Do they all go in and out? My steering wheel only goes up and down.

oldskewel

iTrader: (1)

My 200+k mile '91 has no problems with any motors. The only one in the whole car that has failed so far was the fuel pump, which soft failed at around 195k miles.

It sure seems weird that ALL of your motors appear weak, which is why I was (and am) thinking of a central issue like a weak battery that could be causing it.

The fact that they work 4-5 times in a row and then are weak sounded to me like a weak battery that had some surface charge that could supply the motors for a while, and then after that was depleted and it needed to rely on the chemical energy (which would be weaker in a weak old battery), the motors would slow down due to reduce current availability from the battery.

The 14V when running shows your alternator is good, and if you get the same motor performance while running like that, then you can probably rule out the battery. Still, see how it works with a charger on there.

Regarding the friction / lubrication idea, I don't see how that would explain things working fine 4-5 times and then getting slow ... unless the friction means that 4-5 times is the equivalent of 20 times on a normal window regulator. But even then, ....

The heat idea makes sense. It is common to put thermal protection components (typically a thermistor) in motor circuits to protect against high temperatures. As a motor gets hot (as it may after wear causes a reduction in speed and increase in resistance, or simply when a motor stops due to end-of-travel), the thermistor's resistance will increase, reducing current to protect the motor from burning up.

But still, it seems odd that all the motors act the same way, so I'd be thinking of a central component failure rather than that you've got the same failures in all of your motors the same way. Centralized connections, like the big fusible links, or even the individual fuses.

Sorry, no answers. Just some facts, ideas, and opinions. Good luck.

Yamae

Nobody points out the PTC thermistor built in the motor. I worry that your problems are related to this part. Many of motors used for automobiles have it inside to prevent fire hazards. Aged PTC thermistors tend to increase the resistance or the Curie point shifts to lower temperature side. This causes the motor not to work fully. See the photo here. It's the PTC thermistor. The manufacturer Murata calls it Posistor.

This part tends to fail when used in a place where the humidity is very high. Many flooded cars have this problem too.

peterls

If you replace one of those motors with a brand new one, and it works fine even after 3-4-5 uses,then you know it is the thermistors. If not, and it still slows down after a few uses, than it sounds like a power supply (battery/alternator)

mcgrizzler

Just for safe measure I tried it with the battery charger, same thing. But definitely a good idea to check! After playing around some more with the car I have found that a few of the motors seem to have a slightly different variance (the rear windows go up and down 7-8 times before slowing down, and I had forgotten to check the motorized seatbelt motors and head rest on the passenger side, which do not slow down at all)

I'm thinking the thermal protection theory may be onto something, I've owned quite a few older cars with motorized parts (volvos, benzs) and feel like I have an ok idea of what a dying motor is like. (the head rests on my benz were just lazy and unable to move without assistance even after grease). The thing is all the motors in this car sound really healthy and move the part quickly until a few tries and then just stop.

At first I was thinking there was some sort of centralized unit in the car handling this but now that I've found that the rear windows react a tad differently, and that 3 motors appear to be ok, I'm thinking it could be the thermosistors in the motors like Yamae mentioned in a later post. I'll have to take one apart and try replacing one to see, but will also be in the door panels at some point here so will make sure to grease up the regulators and window channels when I get a chance.

Thanks for the help

Thanks for the tip, that's genius, I didn't realize these motors had a form of thermal protection. I'm going to try and find one that's easiest to remove and try and replace the thermosistor on it just to see if that fixes it. While I don't live in a terribly humid area, it does tend to get semi humid in the late summer months. I am sure the car was never flooded

Thanks, I'm going to try replacing one and see how that goes, after some further inspection it seems some act differently so I think there's a good chance that it has something to do with that. I finally got the carfax in on the car and it looks like the alternator was replaced 5,000 miles ago by a shop that reported it, the battery is also about 2 weeks old, I have the receipt from the lady so I'm hoping that's nothing to do with it. Haven't had a good chance to get into the electrical yet, spent the weekend fixing an oil leak from the valve covers and doing a tuneup, capacitors just came in the for ECM so thats definitely next to see if I can get rid of that P1600 code.