560Sl Electrical Questions

[Litton]

I have a couple of electrical problems that I can't quite come to grips with.

Windshield washer pump does not work.
Radio is completly dead.....acts like no power and the ant. doesn't move.
Cruise control is dead.

I changed the associated fuses for these items and do suspect the cruise control problem is the amp.

The radio bothers me as I have never had one just completly die unless the fuse went bad. I am wondering if there is a relay or some other component that could be involved.

The WW pumps are usually very reliable also which is why I am looking for any common ground.

Car only has 74K miles and is in excellant condition.

I appreciate any hints.

[Strife]

Originally Posted by Litton

Windshield washer pump does not work.
Radio is completly dead.....acts like no power and the ant. doesn't move.
Cruise control is dead.
I appreciate any hints.

1. Really, really check the fuses. The interface between the aluminum of the MB fuses and the brass of the holders can corrode. Many people have performed electrical miracles on their SL's by just twisting the fuses back and forth a bit. I bought brass tipped fuses on eBay and replaced 'em all. Be careful because these are very trecherous to replace and you could burn yourself, even if you have the proper tool to do it. In my case, I disconnected the battery before I did it. Naturally, replace with correct values as shown on the label.

It might be worth the $10-15.00 and an hour of your time to replace ALL of the fuses with brass tipped ones before proceeding on any electrical problem.

2. On the windshield washer pump, I had several problems. Firstly, the pump really was dead (check that your ARE getting power to it) - but this is an extremely easy R/R. You should get the motor/bottle gaskets along with the pump when you replace it, or you will have a working pump with a leaky bottle.

The second and third problems were:

-A check valve from the reservoir to the hoses was leaky and would drain back fluid. This is fairly inexpensive to replace and very easy to accomplish.

- The fluid nozzles, particularly on "garage queens" or cars that don't get driven in the rain (like mine) tend to get clogged with dirt or wax. Obtain a very fine wire and run it through each nozzle (newer cars have dual nozzles on each unit). Do not use an oversize wire and try to force it into the nozzle.

[Litton]

Appriciate the reply. Yep, today I replaced all the fuses with the copper element fuses. No help. The radio is the one that baffles me but I suppose it could have gone "dead".....just not a typical problem.

[halman2228]

I noticed in your post that both radio & antenna died. Last week I found out that if the antenna ground is disconnected I have no power to my radio ('84 500SL). You might look at that to see if it's loose/off ( a braided copper strap from antenna asembly to body) .

[dangill]

I don't know if the wiring is the same but in a previous car I owned
there was a "supplemental" buss type glass fuse in a separate black twist holder buried below the fuel pump relay in the fuse box.
It controlled the radio and something else but my memory fails me.
Just a thought!
Dan

[droederer]

To check the washer pump you need to engage the washer switch. You should have 12V on the pump the vi/yl wire should be+ and the br wire is ground. You can check with a volt meter or test light. If you have 12+ volts replace the pump.

If you do not have 12+ volts and the wipers work you will need to replace the washer switch. Most of the time it's the pump.

The Radio power comes from F1 you should have +12volts to ground on pin 2 of the radio the Red/Green wire. If you don't have power on the radio the ant. will not work. The blue wire from the radio is the Ant. control.

The Ant power is supplied from Fuze 12, 8amp. You can check it to ground on pin2 of the ant. it's the red wire. Pin 5 of the ant is the control from the radio the blue/white wire.

Hope this helps
Dave
86, 560SL

[ericgr]

look at the electrical diagram for your car (get a CD if you don't have one, see ebay or FastLane) and see if any of the failed components are on a common ground or common voltage path.

Consider a bad ground and thus the need to reground. As these cars age, the components become noisy, wires brittle, etc. Sometimes it's difficult to maintain a good ground. So regrounding the circuit somewhere else on the chassis can help.

Look for something ungrounded in the car. Per other poster, look for no ground/bad ground at antannae for example. Look for loose wires for any car components you can easily get to.

If you have other assorted electrical problems, consider the over voltage protection relay (OVP) which is located behind the glove box on the 380SL, I think the same on yours.

If you can't get to this at the fuse box and can't find a bad ground somewhere in the car (e.g. as suggested by another poster) then you need to start removing things (radio, etc) and go in there with a multimeter and start to trace it out. You need to be able to verify good ground-- do that by measuring for continuity between a ground on the chassis (put one lead of the multimeter there) and on the ground wire coming into the radio. All multimeters have a simple continuity test mode. If the multimeter beeps and says continuity, the ground is good. if not, it's not. Then using another ground verify voltage to the radio. Use this method troubleshooting through the system. If for any reason you choose to measure current, you do that IN SERIES with a +volt wire (e.g. between a device and the wire offering +12 volts). Do not put the multimeter in current mode and then try ot measure current betweeen +volts and ground. That's shorting out +volts to ground, bad.