the W123 has a problem - Page 2 - PeachParts Mercedes-Benz Forum

TylerH860 · #16 04-23-2009, 05:44 PM

Yikes, I got your PM. Hope you can figure it out.

79Mercy · #17 04-23-2009, 05:59 PM

OK that relay is for the power windows. Right before I pulled into my neighborhood I put the drivers side window up.

So the question now is should it get hot?

Brandon_SLC · #18 04-23-2009, 06:17 PM

Maybe your power window switch got stuck?

79Mercy · #19 04-23-2009, 06:18 PM

no it isn't stuck, I checked

lietuviai · #20 04-23-2009, 06:33 PM

Relays should not get warm. Warmth is a sign of electrical resistance and a possible voltage drop is occurring somewhere. Inside the relay are a set of contacts that are activated by applying lower current to a solenoid that in turn opens or closes the contacts supplying higher current to whatever accessory it controls. Overtime the contacts get pitted from the higher current arcing them every time they are switched on an off. Sometimes these contacts stick and other times they get so pitted they no longer get contact. In your case it sounds like they could be sticking. It could also be the windings in the solenoid are getting old and are losing their insulation. That could cause a short in itself.

jt20 · #21 04-23-2009, 06:39 PM

mine gets warm as well. - just checked.

certainly not hot, mind you. - but warm definitely.

I don't understand how you could have sensed the warmth from this relay under normal conditions.

jt20 · #22 04-23-2009, 06:42 PM

Lietuviai (first try on that one!)

The solenoids require electrical current to keep the relay in the closed position - current generates heat, the solenoid is an electrical load (a resistor)

akimball442 · #23 04-23-2009, 06:46 PM

That's not exactly true. I just looked at the schematic. The power window relay is a constant duty relay. It is turned on by the ignition switch to allow power to flow through it to the window switches. Relays are used to switch large current sources, and that's what this one is doing.

Since the relay is on any time the key switch is on, it's coil will get warm, or even hot, and this is completely normal and OK.

79Mercy · #24 04-23-2009, 07:00 PM

OK I just found a new problem. I switched out the relay for a different one from under the hood and it go warm as well. So I switched the keyoff and got out of the car and smelled that buring smell again down near the cruise control actuator. Well I ran my hand farther down and the ballest resistors were effing HOT!!! I burned my hand on them.

So I called my personal mechanic again and he said to disconnect them and see what happens. He has a hunch that the ignition switch will get really hot since the ballast resistors aren't soaking up the heat. I haven't done this yet but I will when I get back home, I have to leave right now.

Thanks again everyone for all the help.

lietuviai · #25 04-23-2009, 07:16 PM

Quote:

Originally Posted by jt20

Lietuviai (first try on that one!)

The solenoids require electrical current to keep the relay in the closed position - current generates heat, the solenoid is an electrical load (a resistor)

Good job.
Heat is caused by resistance and vice-versa. I guess I didn't come across like I wanted to in my reply. Reays also come in two different varieties, normally closed and normally open.

compress ignite · #26 04-23-2009, 08:36 PM

79 Mercy,

I know what they are,and their function...But I've never seen on An MB.
ANY chance you've a Picture? (Or a Part number?)

79Mercy · #27 04-23-2009, 08:56 PM

The ballast resistors are mounted to the drivers side fender well. There are 2 here they are
http://catalog.peachparts.com/ShopByVehicle.epc?q=1979-Mercedes--benz---80ce-Engine--Electrical&yearid=1979%40%401979&makeid=63%40%40MERCEDES%2DBENZ%40%4063%40%40MERCEDES%2DBENZ%40%40X&modelid=6150%3AMBC%7C1492%3AED%7C10000026%40%40280CE&catid=240798%40%40Engine+Electrical&subcatid=240864@@Ballast+Resistor&mode=PA

compress ignite · #28 04-23-2009, 09:49 PM

Only thing I've found like that,in the W124,is used as the "Step Down" for
the Low Speed Auxiliary Fans.

Terrible sets of Conflagration Pictures (In Both W123 Chassis) !

1.I'm gonna start with an inline 1/4 Amp fuse for the Cabin Air Temp Sensor Fan.
('Cannot seem to find anything smaller ,Yet!)
2.1 Amp inline fuse on the positive side of the Auxiliary Water Pump.
(As close to the source as possible)(I'm gonna try a 3/4 amp inline first)
3.The Chassis was fitted with one of the Exterior (Of the Fuse-box) 30 Aluminum Strip Fuse holder for the Cabin Blower Fan.
[Anybody know if these fuses are Fast or Slow-Blow?]
(I think I'm gonna retrofit an ATO/ATC type fuse holder and go with a 25Amp fuse.)(A healthy Blower Fan [Good Bearings and Brushes should draw less than 25 Amps.] )

The Auxiliary Electric Radiator Fans Relays are of course another concern.

Leituviai, has your BR answer...if they didn't get hot and "Relieve" all the
Resistance Stress (into heat) You would've already had an "Un-Authorized
Bar-B-Que"!

79Mercy · #29 04-23-2009, 09:57 PM

What does that have to do with my extremly hot ballast resistors?

lietuviai · #30 04-23-2009, 10:02 PM

I've always seen that ballast resistors run hot. That's why they have ceramic holders.