What does 400E first gear start relay do?
 

I read from the previous post regarding which gear 400E starts at, that 400E starts from 1st gear all the time.

Today when I browsed schematic diagram of 1992 400E, I found on page 164, there is a diagram specially for first gear start relay.

This relay seems to be controlled by the LH unit, in the schematic, it actually is in parallel with the Kickdown switch that locates under the gas pedal, so when it engaged, the effect is the same as kickdown.

Does anybody know what this first gear start relay does? does this indicate 1992 400E normally start in 2nd gear?

I feel my 92 400E extremely sluggish from stand still, but once speed is up, it's just like a bullet,

I know the extra high gear in rear differential hampers the low speed acceleration, is there anything else besides this?

Mine starts in 1st, and my buddy's '92 400E does too. Don't know about that relay but am curious.

There is another system designed to delay the 1-2 upshift while the engine is cold, to heat up the catalytic converter faster, but the relay you're describing doesn't sound like it's part of that system.

Steve

My 1992 300Ce has first gear start always.

Try this. accellerate normally, and count the shifts. if you have a 4 speed tranny whichI believ si in that car as is my car, you should get 3 shifts, 1-2, 2-3, 3-4

If it starts in 2nd gear you'd get 2 shifts - 2-3, 3-4

If you plant your foot down all the way hitting the kickdown and you gett he 3 shifts, but not when you dont hit the kickdown, I would deduce it has second gear start.

Try this for your car as well as some benzes have this feature...

Look for an Arrow with a "B" pointing to the right on your shift gate. that will enage first gear - my brothers 85 380sl has it, my dads 94 sl600 has it, and my moms 87 560sel she used to have had the B switch for first gear start.

on 2nd gear start cars, you drop the shifter to 2, then back it up to drive and when you take off it should start in first...

Hope that helps you determine if your car has it or not.

That relay might control something witht he kicjdown when it is pressed at hgigher speeds to stop it from lets say kicking down to 1st gear when doing 80 and ya hti the kickdown switch... so perhaps the relay is to put it in the right gear depending on speed whent he kickdown switch is activated. Wow I hope I am right, I used deducing to come up with that one right outta my head.. :) hehe

Alon

Thanks Ashman, it seems my 92 400E always starts from the 1st.

I finally found out this from service CDs:

On model 124.034 (400E), to enable the catalytic converter to heat up more rapidly, the 1-2 upshift in the automatic transmission is retarded at a coolant starting temperature<40C as follows:

After a speed of 8 km/h is exceeded for 8-13 s or up to max. 38km/h.

This is controlled by the LH control unit and the 1st gear starting off relay:)

So they shouldn't call it first gear start relay, it's actaully a upshift delay relay.

Hey guy here are my two cents. My 400 E also starts in 1. On this site there is a thread that explains the component in the transmission that controls this and how to alter it if you want. As far as the slow start I have found that if I hit the gas from a dead start the initial preformance is a little sluggish but if I hit the gas ALL the way to the floor including depressing the kickdown switch I burn the tires off in a way not for the faint of heart. Maybe the switch tels the computer a few things about air fuel demand/mix under Full demand instead of the tps communicating throttle position. Don't know just glad it does.

Take care
Brian

If my E420 starts in 1st gear,
then why did they put the 'b'to
start in first gear?
:confused:

Hey Manny good morning. We're talkind about 400 E's not 420's

I understand the first gear start was only done for two years..don't know if that is true, it's just something I read on a thread here. My shift also has the same position by the way but it is used to manually restrain the upshift.

Take care
Brian

Gotcha!Thanks :)