What relay is this please?

jontyash

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Hi All,

Broke down again this weekend and had to call out RAC again. After removing the back seats, door trim and loads of other interior parts, the idiot phoned the support team who told him that my problem was due to the relay. Trouble is, the last RAC guy said it was a different one last time I broke down.

This is what happens: The car starts fine, then cuts out straight away.
There was no noise from the fuel pumps down by the back wheel so the fuel pump relay is the instant choice.

So, he took out this relay and tapped it, then put it back in:


but the other mechanic took out the one on the right (below) with the red top on. This one has 2 10amp fuses in the top of it (both are fine) He said it was an after market add-on??? :crazy:



Also, how do you get this red cap off the auto transmission fluid bit? Had a quick look and couldn't suss it out...



So, can I get this part (the top one 002 545 9205) from anywhere? Like Camberley Auto Factors? Do you all think it is this that is the problem?

Thanks everyone, as always! :bannana:
 

SilverSaloon

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Hi.

There shouild be a fuse inside the relay - 10amp. Check its not blown. I believe that part is the OVP relay.

There should be a dipstick on all 124's as far as i know(?).... the cap is there to seal the dipstick tube if its not there. They break if they are removed (intentional)..... but this is usually the case on later mercs. you could buy a 124 disptick or get from the breaker and replace the cap. Probably cheap to get the cap from any dealer but i would replace with a dipstick from a breaker.

i could be wrong though
 

BlackC55

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The larger relay is the fuel pump relay. The other one is an OVP.

Both of these can fault and cause those symptoms.

That dipstick has a lever under it to flip it open.
 

W210 Fan

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I had the fuel pump relay go on mine, took it to bits and re-soldered a dry joint - took seconds, a dry solder joint would probably be your problem in either the fuel pump relay or the OVP relay,
 

Will

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Yep, both those relays have been correctly identified by SS and BlackC55. Fairly common items to fail - so not an unlikely suspect in either case. There's some fairly easy ways to test if they are faulty.

In case of a breakdown, I'm pretty sure you can bypass the FPR by way of bridging the terminals (30 & 87). Would be good to eliminate the FPR if it happens again also, to confirm the diagnosis if you're unsure.

Sounds very much like a faulty FPR from what you say (I've had exactly the same symptoms with an old 2.3-16 years ago).

Could try and re-solder it, or perhaps get a spare part from a MB breakers etc. Shouldn't be that expensive :)

Will
 
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jontyash

jontyash

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Brilliant thanks guys. That's awesome. I'll have a look and see if I can solder it up first, then perhaps try a new one if that doesn't work. Brill!
 

neilrr

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Hi.

There should be a dipstick on all 124's as far as i know(?).... the cap is there to seal the dipstick tube if its not there. They break if they are removed (intentional)..... but this is usually the case on later mercs. you could buy a 124 disptick or get from the breaker and replace the cap. Probably cheap to get the cap from any dealer but i would replace with a dipstick from a breaker.

i could be wrong though

No offence SS but if you don't definitively know the answer why post? The OP could have broken his dipstick following these instructions.
 

SilverSaloon

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No offence SS but if you don't definitively know the answer why post? The OP could have broken his dipstick following these instructions.

Well some info is better than no info. I did put "i could be wrong" so the OP shouldnt take what i say as gospel.
 
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jontyash

jontyash

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Well, I took out the relay, pulled it to bits and had a good look at it. It looked perfect in every way. I couldn't see any broken solder joints or bits on the pcb...damn it. I've just got to pull the other relay out (the one with the 2 red 10 amp fuses in it) and have a look at that. It went dark tho so I'll have to wait till the morning.

Also - still can't get the red cap off and I can't see a lever?? Looks like i might have to break it after all??
 

neilrr

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Jon,

Just pull the two fuses out of the top of the OVP & examine them first before you get adventurous & start to take the relay itself apart!

Needle nosed pliars will pull the blade fuses out.
 

SilverSaloon

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Hi again,

I have just gone out to my W124 (1995) to take a look at the gearbox dipstick.... Both my 124s have black dipstick tops which makes me wonder why yours is red..... and doesnt look the same shape as either of mine nor the pic below.... which makes me think its just a cap

If you turn the cap you should see a plastic handle-type thing attached to it.... lever/pull this up and then the "cap" should just pull out along with the dipstick. if you still cant see one after turning the cap, then get a torch and look to see if the lever has broken off - and try to prise whatever plastic is left to remove it....

if that doesnt happen, then i do suspect you have a later Merc cap fitted... maybe the previous owner nicked / lost the dipstick and replaced it with the cheaper cap...? You could carefully try to prise it off with a large flat bladed screwdriver.

make sure its the cap before you break anything and not the top of the dipstick.... if its the real dipstick then nothing needs to break to use/remove it.

This is what you are looking for (note the plastic handle bit on the top).

 
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W210 Fan

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I had a simliar age vehicle and the cap was red on it so its the earlier dipstick, be carefull pulling it out as if you snap anything off and it falls into the tube guess who taking the gearbox for a flush as they have put small lumps of plastic into it...
 
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jontyash

jontyash

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Thanks guys - update. I checked both the red fuses on the OVP again and they're definitely fine so I'll go to stage 2 tonight and open her up...:eek:

Also had another look at the red cap - there's defintely no handle on it - it looks exactly like the one in your picture SS but red and no handle?? I'll have another look and see if I can see where it snapped off - it went dark in the end last night...damn the winter time.... I think though, if it works the same way as the one in the picture below, then if I push in the right place with a screw driver I might get it free...eek.

Thanks for your comments too W210 Fan... I must admit, I hadn't thought about having to flush the gear box if I dropped bits in...

On the upside though guys I changed the spark plugs, air filter and HT leads last night. Also cleaned the top of the carb with carb cleaner and got 20 years of crap out of there. What a massive difference!!!!!! At least 50bhp. Can't beleive it. :bannana: :bannana:


The rubber on the old HT leads had started to crack and had gone sticky where it was so old!! Well chuffed...
 
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jontyash

jontyash

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W210 Fan..

"I had the fuel pump relay go on mine, took it to bits and re-soldered a dry joint - took seconds, a dry solder joint would probably be your problem in either the fuel pump relay or the OVP relay,"

What does a dry solder joint look like please? ...all the ones in the back of my relay were really shiny and looked like new. I checked that they connected to the pcb correctly and they all seemed to and I couldn't see any cracks in the pcb wire.

Am I missing something? Does a dry solder look brown in colour or anything like that?

Thanks, J
 

wheelbarrow

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Dry Solder Joint

I've just resoldered the joint from the zenner diode (the thing that looks like a button cell battery) to the flat-blade fuse holder on my OVP. The dry joint was obvious using the handlens on my swiss army knife. The dry joint was a copper coloured area. Also found one on one of the resistor joints, again only visible with a magnifying glass. Have yet to verify if this has fixed my very intermittent misfires. I'm checking the FPR later today as well.
 

grober

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dry joints

This excellent site gives a good pictorial explanation of what to look for in a dry joint. Sometimes however if the dry joint is caused by a long term stress fracture from vibration its almost impossible to see. Hence its a good idea to just remelt the solder on every joint you can see on a PCB to be certain but take care not to thermally stress any component by keeping the soldering iron on the joint for too long. As soon as the solder has liquified that's enough http://dragon.herts.ac.uk/~eleqdml/teaching/general/soldering/
 
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Dec

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Very useful grober, should be in the How To section.

Dec
 
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jontyash

jontyash

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Brilliant thanks guys, that's just what I needed. Really helpful. I'll have another look.
 

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