What does the OVP do in an 84 SD?
I know it is connected to the tach. What else does it run?
Seems like the OVP has different functions for different years & cars.
Also, what are the two things pictured?
A tach amp? And a fuse for something--both on the driver's fender.


Just trying to figure out some little mystery parts
I still don't know about

TIA
Jeff

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__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

An OVP is used to protect sensitive electronics. On your SD you will have an electronic speedometer as well as probably ABS?



This is a diagnostics socket as you say probably for the tach amp

The other picture is probably just a connector. Take the cover off it and have a look.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks, Stretch.
Finally got the top off the tach amp plug and that's what it is.
It was really stuck---probably hadn't been unscrewed since birth.
The other ones I've seen are taller.
The other object has an 80amp fuse in it like the one in the glow
plug relay. It disappears under the fusebox.

On the OVP--I don't have ABS. Just can't find any info online on
what that relay controls besides the tach on this year car.
Can't find anything in my FSM but it is missing some pages in the back.

There's always one mystery left to solve.

Jeff

__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Don't know about the 84 SD but on my 85 300D, the "tach amp socket" is actually a diagnostic port/ socket. The difference from a real tach amp socket is that the diagnostic socket does not have an output pin that goes to the tach in the cluster. The 85's tach uses a sensor on the flywheel (whereas the diagnostic port's sensor is on the harmonic balancer). The 85 300D's tach circuitry is in the EGR computer (as opposed to be in a round black module known as the "tach amp" in 83 300D's). In the 85 300D, the OVP controls the power to the EGR computer. It is an unnecessarily complicated design IMO..

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Of course that EGR computer - does other stuff too doesn't it? Like the speedo? (Thought I read that somewhere)

As for the FSM trouble =>

Untitled Document

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks for the OVP info, Funola. A work in progress from year to year, no doubt.
I figured out the fuse. There is a mod to the AC compressor fuse--#11,
which had a history, IIRC, of blowing all the time. I think this was an
MB approved workaround and I bought the car with this setup.

The #11 fuse is bypassed to the thing in the photo and the 80amp fuse
on the fender is wired into #11 spot under the fusebox.

Jeff

Thanks for the link, Stretch!
I've been around I while, so I still remember you as Army.................

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__________________
1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Looking at the Startek wiring diagram on the OVP for the 84 SD, it looks almost the same as the 85 300D with the exception that the OVP also powers the ABS controller (which most 85 300D's do not have), in addition to powering the EGR controller.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Ahhh - those were the days!

(You can't stay in forever - you get too old and have to move back to civilian life)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!