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  #16  
Old 09-18-2018, 09:53 AM
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Quote:
Originally Posted by Mxfrank View Post
Relay points are made of tungsten and are very corrosion resistant. .

Normal relays use a silver alloy not tungsten that is commonly used on ignition points. Some small signal relays use gold plated contacts.

It is desirable for silver contacts to have some pitting as arcing during operation prevents buildup of tarnish / plastic out gassing that will coat the contacts. In systems that have very low currents / voltage relative to contact size, tarnish builds as an insulator causing erratic operation.

To get past tarnish / coating issues, relays used in small signal applications have thin contacts that form an X . ( one contact is / the other \ and when they touch they form a X . ) This small contact area allows for some arcing to keep things conductive.

Sure, a regular relay will " work " for a while but it will become intermittent on operation. Thankfully, small signal relays are mostly used in industrial controls not cars.

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  #17  
Old 09-18-2018, 05:15 PM
E300d 1995
 
Join Date: Jun 2017
Location: Near Lake Texoma
Posts: 480
Close inspection of my comfort modue relay points shows some pitting, especially the normally used front window control relays.

A couple of questions:

1. Does anyone know if the comfort control module relay control circuit uses a capacitor-resistor, a diode, or nothing to reduce contact break arcing?
2. If I wanted to try to keep the pitted relay contacts in service longer what is the best tool to burnish them, fine sandpaper, an old-style metal burnishing tool, or something like paper soaked with a liquid ( alcohol, acetone, ? )

This link is to an 'old-timers' website:

https://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm

After reading this I feel a little more comfortable about using silicone products ( but definitely kept away from relays or other make&break places like windshield wiper control ( and also painted surfaces ).
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  #18  
Old 09-18-2018, 06:03 PM
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Power relay points will always have pitting and ablation, especially on DC circuits. There's NOTHING you can do to prevent it, it's just part of the inrush amperage when closing in on a load. If the relay is working, leave it alone. Trying to be a hero and abrading the points will quickly remove the plating and rapidly cause the relay to fail. This is not a set of breaker points. The plating on the relay points is very thin, sanding them will take the coating off.
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  #19  
Old 09-18-2018, 06:14 PM
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Join Date: Dec 2003
Location: Palm Springs, CA
Posts: 782
Are you having trouble with the relay?I realize this is an older car but cannot you buy a new comfort module from MB? Or haunt the pick n pull yards or find the website that does a national search for used parts.
Anziani
'97 CL600
66K

Last edited by anziani; 09-18-2018 at 06:17 PM. Reason: added sentance
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  #20  
Old 09-18-2018, 09:22 PM
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Most of the cube relays include a resistor for suppression.
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  #21  
Old 09-18-2018, 11:02 PM
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Quote:
Originally Posted by Mxfrank View Post
Most of the cube relays include a resistor for suppression.

Only to suppress flyback ( ringing ) of the coil, not the contacts. This protects the circuity driving the coil.
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  #22  
Old 09-19-2018, 12:57 PM
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ruined vacation once

Had a ford and I always keep my engine area clean.On vacation camping down a long dusty road,at camp,I washed the car. Engine bay too,new to armor all I did all the hose's and plastic and plug wires.
Next day running for supplies car missed bad,stayed a week there,and nursed car home.One night I opened hood in the dark,and saw xmas lights.Dang stuff made plug wires leak,and cross fire.
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  #23  
Old 09-19-2018, 04:41 PM
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Join Date: Nov 2010
Location: TX
Posts: 3,978
On a similar note, I will also not recommend anything on a relay contact pin, however something on a sliding connection (like a spade connector) can help if the design is missing a weatherpack seal.

My neighbor had a ford focus that would throw an input speed sensor error, after 4 sensors, and literally a tube of silicone grease. He asked me for any insight on the trouble, I saw that the connector was missing the weather pack seal and also the center plastic piece that kind of locks the pins in the plastic housing. (the connector was installed and removed way too easily which brought my suspicion)

after pinning a new connector in it the problem went away, didnt apply any grease either, infact washed away all of the grease he slathered on.

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