My 96 C280 won't start; I checked the OVP and it is the newer part number 000 540 67 45 and it appear OK on the outside (i.e., the 15 amp fuse appears OK and I did not detect any electrical paths on the electrical socket nibs). Is there a test I can do on the OVP or is it just best to replace? There were zero warnings for the failure to start - tried to start the other morning and although it seemed at first to catch while cranking over, it never did. The inside mirror does not flash in any manner while cranking and when I turn the key on I believe I hear the fuel pump pressure up in the back for about 2 or 3 seconds.
Any help/recommendations will be appreciated.
Thanks
SocksE420

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SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

You equipped to do a bench test??

__________________
A Dalton

Arthur - I guess that depends; I have a multimeter, test light, etc., - will these be enough?
Socks

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SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

Yeah..just basic circuit stuff ..some test leads , jumpers , and the main thing will be a 12v source..like a battery

Pull the relay and I will match up those numbers with the circuits.

Numbers should go from 1-9.
Have a battery?

__________________
A Dalton

Arthur - I have two sources of 12 volts; my lawnmower battery or my 12 volt battery charger.
Socks

__________________
SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

<< I have two sources of 12 volts; my lawnmower battery or my 12 volt battery charger.>>

Ok.....use the battery cuz a charger can spike the OVP and the zenier diodes will drop the input.


Take the relay and hold it bottoms-up so you are looking at the pins, with the bottom row being the row that includes the one small pin. Put it in a vice or some holder.

So , the number for each row of pins as they face you , will be :

Bottom row ..L to R
1,3,5
Middle row L to R
2,4,6
Top row
7,8,9 ..L to R

Bring 12 v + to pin 1
Bring 12 v - to pin 5
Alligator clips work well here.

Now , take the test lamp and hook one lead to the battery - [ this lead stays there for all test]
Test pin 1 and 9 with other lamp lead ..lamp should lite.
Now , jumper wire pin 3 to pin 1..that should energize the relays [ there are 3 in the 000-540-67-45] and you should hear them click. If YES,
Test lamp lead at 2,7,and 8. All should lite.

Last test requires ohm meter set to continuity.

With jumper from 3 to 1 still in place , you should have continuity across pins 4 and 6. No voltage on this test , just cont. b/c it is a switch inside the OVP.

When the jumper from 1/3 is removed , all those voltages should go OFF and the cont test at 4/6 should show OPEN.
I do the jumper from 1 to 3 with a screwdriver so I can do it several times while watching my test lamp and meter to make sure they make contact every time.

If any test fail, tell me which.
If none fail, then I will tell you how to do the feed test to the OVP at the socket plug in the car that the relay connects to.

If you do not understand any of this , ask BEFORE you burn something up................

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A Dalton

Arthur - appreciate you walking me through this - regarding the test lamp, mine has an alligator clip and an ice pick point - when you say "hook one lead to the battery" do I put clip on the negative or positive post of the battery? I'm thinking it goes on the negative. When testing 2, 7, and 8, the jumper between 1 and 3 remains in place, correct?
Thanks again
Socks

__________________
SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

< mine has an alligator clip and an ice pick point - when you say "hook one lead to the battery" do I put clip on the negative or positive post of the battery?

Re-Read my instructions.
It says " Battery - " ...not "Battery + "

You have a standard test lamp ..the point is + and the clip is neg in most cases , but it can be reversed b/c a test lamp is not polarity sensitive.

And b/c in this test we are using the tip to read 12 v.+ , we want the clip on the battery NEG [ - ].
If you put the clip on the POS, your lamp will not lite on any of those test. It needs + and - to lite........that's all.

If the tests were in-situ on the car, I would have just said to use chassis ground , but b/c this is a Bench test , there is no chassis ground, so you use Battery -. Maybe I should have written out Negative, but that does not cross my mind b/c +/- is commonly used on any DC electrical test instructions .

__________________
A Dalton

What does "OVP" stand for??

What is the correct name if I wanted to order one from parts company?

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Norm K.
'97 E420 Sport
'06 E350 Sedan
'67 Mustang Coupe
'70 F-250
'15 VW Jetta

Over -Voltage-Protection relay..

Mercedes Cure-All......

__________________
A Dalton

Arthur - performed the tests this morning:
- energized pin 1 with + and pin 5 with - from a separate battery
- test pin 1 and 9 with the test lamp grounded to the battery - both pins lit the light
- put a jumper wire between 3 and 1 - heard the click
- left the jumper in place and tested 2, 7, and 8 with the test lamp - all 3 pins lit the light
- left the jumper in place and test and had continuity across 4 and 6; when I removed the jumper, no continuity.
I guess this means the OVP is OK, correct?
Thanks Socks

__________________
SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

Correct.................

__________________
A Dalton

Arthur - is it time for me to do the test feed through the relay socket you mentioned above or continue looking for other possible faults?
One item that occurred to me yesterday was that I may have turned the car off while it was still in drive the last time I drove into the garage; I recalled not being able to remove the key and then I realized it was not in park. Other than putting the gear shift lever in Park and removing the key, I don't recall anything else "unusual" about the shut down.
Socks

__________________
SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

Arthur - problem solved but I now think it was the NSS; I read a post that you participated in a year ago where someone recommend that the gearshift lever be moved from drive up to park without putting one's foot on the brake. In light of my recent recollection that the last time I shut down the car I may have not have the lever in Park when I turned the car off, I thought I would work the NSS approach.
Regardless, re-installing the OVP and going through the NSS routine, caused the car to start.
I will keep an eye on this in the future; while I haven't replaced the NSS, I don't know what the original owner may have done.
Thanks again for your willingness to walk me through all this.
SocksE420

__________________
SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)

If it was NSS , it would not Crank...never mind Not run.

You may have had a poor connection at OVP plug.

If it does it again , I will tell you how to test that coodition...

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A Dalton