GP Relay fixed for $1.29 - PeachParts Mercedes-Benz Forum

nhdoc · #1 08-24-2009, 10:47 AM

The 300TD had been experiencing a "quick GP light" for the past week (the light would go out in a second or two) and finally it stopped coming on at all today along with no glow at all

I removed the glow plug relay and found a 100 microfarad 16V capacitor on the board had "exploded" (well, its insides had pushed out through the bottom). I went down to radio shack and bought a 100 mf 35V cap for $1.29, soldered it in and low and behold the relay is working again and the light stays on for the normal cycle time

Thought I might pass this along since there may be others who experience the same symptoms or have a seemingly dead relay.

RML · #2 08-24-2009, 10:50 AM

I am certainly anything but an electronics expert but wouldn't the 16V vs 35V rating be a problem? Or is that just the upper limit of what the capacitor can tolerate?

nhdoc · #3 08-24-2009, 10:52 AM

Quote:

Originally Posted by RML

I am certainly anything but an electronics expert but wouldn't the 16V vs 35V rating be a problem? Or is that just the upper limit of what the capacitor can tolerate?

You can safely use a higher voltage rated cap, just not lower. If you go way higher you might have problems but 35V instead of 16V isn't an issue...in fact it will just last longer. Electrolytic caps seem to be the weak link in lots of old electronics so they are the component I scrutinize when an assembly fails...in this case it was the culprit.

punky · #4 08-24-2009, 10:56 AM

Yes, that's it's max voltage before it splodes. You can always go higher in replacement.

vstech · #5 08-24-2009, 10:59 AM

the voltage rating is the capacity of the insulation in the winding... so higher is just fine!

rs899 · #6 08-24-2009, 11:11 AM

Capicitors are what usually go bad in the VDO clocks in our cars , so it would make sense that they would be failing elsewhere at the same time. The one or two I have seen were visual failures, too.

This is good to know

barry123400 · #7 08-24-2009, 02:37 PM

Ageing is this type of capacitors enemy. A general improvement can many times be accomplished just by the shotgun approach on all very old type capacitors greater than I microfarad usually.

Many times the downfall of the cruise controls failure to hold settings is the by now infamous c-19 capacitor for example. It's function is to store an average refference voltage.

RML · #8 08-24-2009, 05:43 PM

Are there capacitors on the climate control unit circuit board?

Brandon_SLC · #9 08-24-2009, 10:47 PM

I wish you had posted this in 1980.

I've probably replaced at least 35 relays on the various German cars I've owned over the years. Usually Bosch.

All the self maintenance I've done over the years would have been so much easier with the internet. I've torn a couple relays apart, but couldn't see what went wrong.

But, thanks anyways.