PDA

View Full Version : ? about the relay's


lowprofile
06-29-2013, 01:18 PM
Testing the relays inn the sprinter( mine is a 2006 T1N 3500)

In flowing the directions on how to test a relay I notice that the relay's in the sprinter are
different than the ISO relays described in the how to test.
On the sprinter the terminals 87 and 87a are in reverse order than that described for ISO
relay testing of a 5 pin relay. I guess the only problem with this is that when trying to follow
test procedures :thinking:it gets my old head mixed up.:bash:

autostaretx
06-29-2013, 04:29 PM
It really really helps if you provide links to procedures you're asking about...
different than the ISO relays described in the how to test.
I tried searching for "test iso relay" and only got three hits, none of which appeared to be the procedure.
(i remember the posting from a while ago, but i can't find it)

Let's look at a typical relay from the Sprinter's service manual and images adapted from rsandas.com:

53214

Pins 85 and 86 energize the coil.
When the coil is NOT energized, pin 30 (the "wiper" or "armature") makes contact with pin 87a
When the coil IS energized, the wiper moves over to make contact with pin 87
Great.

BUT there are times (for no reason one can defend) when the car builder (i just checked an old VW manual, and it did the same thing)
(a) only needs the "energized" contacts (like the above diagram, no wire to 87a)
(b) feeds the power being switched into pin 87, and has the "load" (headlights?) attached to pin 30.
**in those cases** it's "legal" (i.e. everybody does it) to call the POWER pin "30" and the LOAD pin "87", even though the insides of the relay would appear to be "backwards".
On the sprinter the terminals 87 and 87a are in reverse order than that described for ISO relay testing of a 5 pin relay.
Maybe he made a typo... if i can't find the page i can't comment on it.

On most relays, the polarity of 85/86 should not matter... some relays have internal diodes in which case the polarity very much does matter. Convention has it that 86 is the positive side.

--dick
added: i fully agree with Amboman: what problem are you really trying to address?
added: the bottom half of this describes ISO relays, too: http://rsandas.com/P1_Session_11-3.html
added: the middle of the 16th message in this thread: http://sprinter-source.com/forum/showthread.php?t=1936 has this description of the ISO contacts:
----------------
The ISO designation for each terminal is molded into the base adjacent to the terminal.
The ISO terminal designations are as follows:
30 (Common Feed) - This terminal is connected to the movable contact point of the relay.
85 (Coil Ground) - This terminal is connected to the ground feed side of the relay control coil.
86 (Coil Battery) - This terminal is connected to the battery feed side of the relay control coil.
87 (Normally Open) - This terminal is connected to the normally open fixed contact point of the relay.
87A (Normally Closed) - This terminal is connected to the normally closed fixed contact point of the relay.
-----------------
...and later in the text describes how it's being used by the window wiper system.
...that was posted in 2008... i'm still trying to find the "how to test relays" posting...

Amboman
06-29-2013, 04:48 PM
Testing the relays in the sprinter


Firstly why ?

Are you looking for a fault or aiming to make one?

To check a relay correctly you need to supply a load current across the contacts whilst the relay is energised and measure the voltage drop in millivolts across the contacts to look for the internal resistance whilst operating.

The other way is just an ohmmeter across the contacts to see if actuating but that's only a casual check.

Aqua Puttana
07-01-2013, 02:13 AM
... On the sprinter the terminals 87 and 87a are in reverse order than that described for ISO
relay testing of a 5 pin relay. ...
They seem fairly standard from my experience.



http://sprinter-source.com/forum/showthread.php?p=221060#post221060

vic