Shift Override Button

[yank30265]

1990 ls 400 dosent come out of shift anymore unless I push shift override button; what is that problem and fix?

Also lights dim when brakes are hit . they dim just a hair but come right back; battery drops down a little when tested and goes right back up to normal; alternator is good.

And how hard is it to get climate control out for rebuild. I found someone on a major auction sight that will rplace the lcd for 75.00 if I get it out and send it to him.

power steering grabs a litttle at slow speeds but not that bad.

If anyone can help me Id appreciate it; one problem or all.

i got more but let me tackle this first. Thanks

[1990LS400]

I'll try to answer a couple of your questions -- need to run.

The most common cause of having to use the shift override switch is a defective brake light switch on the brake pedal. I had two go out during the 13+ years I owned a 90 LS.

You might want to check for corrosion on the battery cables. There are also a couple of fused links that can cause voltage drops when they get corroded.

The climate control is very easy to remove. Pop out the center vents and the wood console -- use trim removal tools and be careful not to break anything. On a 90 LS, you will need to then remove the ashtray assembly -- the bolts holding it will be obvious if I remember correctly. You will need to use the shift override button and pull the gear lever backward to allow clearance. The HVAC control/radio assembly is held in place by only four 10 mm bolts -- two top and two bottom. Put a towel on the center console before you pull the assembly out so as to not scratch anything. Disconnect the cables as you slide the HVAC control/radio out and then separate the HVAC control from the brackets. All this is easier than it sounds.

[yank30265]

I'll try to answer a couple of your questions -- need to run.

The most common cause of having to use the shift override switch is a defective brake light switch on the brake pedal. I had two go out during the 13+ years I owned a 90 LS.

You might want to check for corrosion on the battery cables. There are also a couple of fused links that can cause voltage drops when they get corroded.

The climate control is very easy to remove. Pop out the center vents and the wood console -- use trim removal tools and be careful not to break anything. On a 90 LS, you will need to then remove the ashtray assembly -- the bolts holding it will be obvious if I remember correctly. You will need to use the shift override button and pull the gear lever backward to allow clearance. The HVAC control/radio assembly is held in place by only four 10 mm bolts -- two top and two bottom. Put a towel on the center console before you pull the assembly out so as to not scratch anything. Disconnect the cables as you slide the HVAC control/radio out and then separate the HVAC control from the brackets. All this is easier than it sounds.

thanks; I work in a parts store and my co worker told me the overide button problem was a neutral safty switch; I like your answer better; the battery is pretty greased up with di electric grease so no corrosion there; and yes the removal of the climate control sounds pretty easy thanks again.

[steve2006]

Don't get too carried away, with the symptoms you have check the trunk hinge wiring loom for broken wires before anything else as you will probably find at least the white wire damaged in there which could result in all the problems you are having.

As for the AC unit follow the link below for radio removal and then unplug the orange plug at the rear of the unit,remove the 4 screws ( 2 either side) and the AC control unit is out.

http://www.lexls.com/tutorials/audio/headunit.html

[1990LS400]

Don't get too carried away, with the symptoms you have check the trunk hinge wiring loom for broken wires before anything else as you will probably find at least the white wire damaged in there which could result in all the problems you are having.

As for the AC unit follow the link below for radio removal and then unplug the orange plug at the rear of the unit,remove the 4 screws ( 2 either side) and the AC control unit is out.

http://www.lexls.com/tutorials/audio/headunit.html

You're giving him photos of how to remove the HVAC control? Where's the challenge in that? ;) "One word is worth a thousand pictures!".

Definitely check the left trunk hinge wires -- other common "features" of breaking wires at the hinge are the Reverse indicator in the instrument cluster lighting up when the shift lever is in Drive and a poorly shifting transmission. Broken wires in my 90's hinge never caused me to have to use the shift override button but that could still be a possibility. The wires at the hinge tend to break repeatedly and have to be fixed over and over -- it's a "feature" of the gen 1 LS400.

[93ls400walt]

The brake light switch on the break peddle was the problem on my 93ls for having to use the override button to get out of park. Easy to change if your a contortionist. Note the gap between the peddle are and the switch button before you remove the old one. Set the new one to equal the gap. I think my new switch was around $40.00 from dealer

[VBdenny]

The override button allows you shift out of gear while parked. As to your primary problem, sounds like new battery time for you. These cars use a lot of juice and even marginal batteries can cause problems. Yeah, I know it was tested but it is just a test. Mine acts funny and the battery is over 3 or 4, it's gone.

[fsuguy]

1990 ls 400 dosent come out of shift anymore unless I push shift override button; what is that problem and fix?

Also lights dim when brakes are hit . they dim just a hair but come right back; battery drops down a little when tested and goes right back up to normal; alternator is good.

And how hard is it to get climate control out for rebuild. I found someone on a major auction sight that will rplace the lcd for 75.00 if I get it out and send it to him.

power steering grabs a litttle at slow speeds but not that bad.

If anyone can help me Id appreciate it; one problem or all.

i got more but let me tackle this first. Thanks

Hi Yank,

This is only with regard to the shift override button -

1. First check your stop fuse - under the driver's side dash by pedals (if it's OK, check to make sure battery is good);

2. If battery is good, check the brake lights - any blown bulbs will trigger the safety (disabling the shifter);

3. If all brake light bulbs check out OK (do a visual with someone's help, or back up to a large store window), check trunk wiring in left hinge;

4. Chances are good that at least one of the wires hidden in the left trunk hinge are broken inside their insulation; feel each wire for limpness, otherwise you may have to actually cut each one to check for a broken one;

5. If all the above check out good, then check the light failure sensor - it will be behind the trunk upholstry on the left hand side - a little, black plastic box (about 2.5", by 3") with a single wire harness going to it.

I had the same problem with shift override switch being only way to get into gear - had three problems:

1. A short in the RH brake bulb housing, probably due to heat damaging the insulating plate;

2. Broken ground wire in the trunk hinge; and

3. Break in the circuitry in the Light failure sensor - fixed with a soldering iron and about 5 minutes work.

Good Luck

[RDM]

The brake light switch on the break peddle was the problem on my 93ls for having to use the override button to get out of park. Easy to change if your a contortionist. Note the gap between the peddle are and the switch button before you remove the old one. Set the new one to equal the gap. I think my new switch was around $40.00 from dealer

What is a "break peddle"?

[eatingupblacktop]

What is a "break peddle"?

Lunchtime cycle?