Fuel pump relay questions - W202

[smb]

Hi there

I've got a 1994 C220 automatic (W202) and have a few questions about a relay (p/n 0015429619), which I assume from Google searches is the fuel pump relay. If you follow Dec's post (http://forums.mercedesclub.org.uk/showthread.php?t=62702) about the solder repair of the N10 relay, then the relay I'm talking about sits just to the right of the N10 relay. (Those slots are empty on Dec's photos unfortunately, but you can see those locations on Pics A&B).

Anyway I'd recently purchased this car and while going through the repair job on Dec's post, I noticed that there is a fuse which sits on top of the fuel pump relay and it was blown - and also that it looked brand spanking new (ie recently replaced). I was concerned about a brand new fuse getting blown (cos this means an expensive electrical fault elsewhere) and took it out for replacement. Only when I was about to put in the replacement did I spot that on the relay, it is clearly marked "12V 30A". And the replacement fuse, and blown original fuse are both 15A.

Now I suspect that the reason the fuse blew in the first place is cos it was a 15A fuse which was inserted where a 30A fuse should've gone. This was probably the doings of the Dodgy Dealer that sold me the car in the first place. So now I've got a few other questions to ask - hopefully someone can shed some light.

1) Should I replace the fuse with a 30A or a 15A?

2) Is there a diagram or card which actually shows the correct amperage fuses for my model? (The card in the fusebox tells me what the fuses are for, but doesnt give the correct amperage, so I'd have to revert to the Dodgy Dealers decisions and just replace with what was there before).

3) What does this relay actually do: I've seen it called a Fuel Pump relay, and also a Multi purpose relay. What other purposes does it have?

4) I've been driving the car for about 4 months and have only recently spotted this blown fuse. I've since driven it a further ~week with the blown fuse. Is it possible to do use this car without a fuel pump for >4mnths, under normal circumstances (ie: Did the Dodgy Dealer short-circuit something to make the relay work without the fuse?)

Thanks,

 

[television]

That fuse is on the OVP relay, it should be 10amp, this has nothing to do with the fuel pump relay or the N10 multifunction relay

at the top here

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1997/C230/SYSTEM WIRING DIAGRAMS/6087.pdf

 

[Dec]

If the fused relay you refer to at the N10 relay is blown then something else in your car isn’t working, unless SA cars are different to those in UK, in the UK the fuel pump relay is in the boot.

If you don’t have the fuel pump relay in the boot as pictured below then perhaps SA cars have there fuel pump relay beside the N10 relay.

The diamond and circle and square symbols (In picture above) symbolise the fuse rating, for example a Square symbol is 30a and a Circle symbol is 7.5a


Dec

 

[smb]

Thanks guys. I found the fuse amp rating on the card.... missed it completely when I checked previously.

I've taken the relay out and done a google search on the part number as read off from the actual relay ie ("mercedes benz 0015429619" in the search box) and got a lot of results related Fuel Pump relay. So I suppose that SA and UK have slightly different designs (ours is next to the N10 relay). I'll check the boot fuse box anyway just in case I need to replace a fuse there as well.

 

[smb]

... now THATS weird.

I just had a look in the boot. And there's another relay there with the same part number 0015429619. It has a 30A fuse (not blown). Its exactly as shown in Dec's photo.

So I have two of these things.... one in the boot still working and one in the engine compartment with a blown fuse (which doesnt match whats written on the part).

Why the dickens would there be two identical relays? Is it perhaps possible that my OVP relay isnt where it should be, and someone dodgy put a Fuel Pump relay in there, perhaps that slot where I found it (next to the N10) is only provided to house a spare?

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I've now had a careful look at my fuse boxes and found several cases where a higher rated fuse was put where it should not have been (eg 15A fuse in a 7.5A socket), presumably cos the person didnt have spare fuses with the correct rating. I'm upset now cos that defeats the POINT of having a fuse in the first place. In the boot, I found the mounting board where all the fuses actually fit in, was placed back-to-front and just hanging loosely in the area. I turned it around and it just clipped neatly into place..... (but why would someone DO something like this in the first place?)

So the way I see it now, is that I've got two fuel pump relay switches and no OVP relay switch. Its the one that should go next to the N10 relay into the slot marked "D".

Just to be sure, can someone tell me if the OVP relay would physically "fit" into the same place as the Fuel Pump Relay? I had initially assumed this is impossible cos the switches were engineered to only fit into a one specific location.

 

[Dec]

Maybe, in the past, someone may have used a fuel pump relay to run auxiliary head lamps or spot lamps or something else, there would be more than one use for any relay.

Either something isn’t working in the car or it has been removed OR perhaps this relay.. at the N10… is bypassed.

The OVP would not be in with the N10.

Dec
Edit, passenger side location of OVP pictured below.

 

[smb]

OVP relay

I found the OVP relay... part number is 897219000 and it was located under the plastic computer box cover.

I expected to find a 10A fuse there, from what television posted earlier, but instead found a 20A fuse. The switch itself has a 15A etching on the plastic so I put a 15A fuse in there and kept the 20A for a spare. The fuse itself has a round plastic cover and felt quite warm when I took it out.

Thanks for the help guys - much appreciated.

Now I just wish I knew what should be in that "D" slot next to the N10 relay, and why the 15A fuse blew if the slot is bypassed.

 

[Dec]

Does the fuse blow immediately you insert it or does it blow only when the ignition is switched on or does it blow only when you turn something on, for example the high beam headlights?

Best not to use it with a fuse until you know what it controls, whatever it controls may have been removed and its wiring may not have been tidied up correctly or perhaps its not suppose be in there at all and has no purpose other than being a spare fuel pump relay .

Dec

 

[television]

I do not think it should be there at all,if every thing works leave it out

 

[smb]

Hi... the fuse was blown the first time I checked. I havent replaced it yet, as I agree (as pointed out) to rather figure out what it does first.. Which in my case translates to "keep a 30A fuse handy somewhere and leave the relay alone"