Alternator or not??

[Jm123]

Morning,

My 1989 300Se auto is back playing up again.

I just need to know if my alternator is finished or not and some ways to test it. Basically, the electrics cut out sporadically starting with the stereo dipping in and out until the whole thing grinds to a halt and the car doesn't even turn over. After a while it'll start again but will cut out within a few minutes.

Prior to this starting the indicator light fuse was blowing....i'm not sure if this is linked or not.

It's make or break time for me now....i can either fix this or i dig the walking boots out of retirement!!

Thanks in advance gents.

 

[eric242340]

Morning,

My 1989 300Se auto is back playing up again.

I just need to know if my alternator is finished or not and some ways to test it. Basically, the electrics cut out sporadically starting with the stereo dipping in and out until the whole thing grinds to a halt and the car doesn't even turn over. After a while it'll start again but will cut out within a few minutes.

Prior to this starting the indicator light fuse was blowing....i'm not sure if this is linked or not.

It's make or break time for me now....i can either fix this or i dig the walking boots out of retirement!!

Thanks in advance gents.

From what you have posted, and im still pondering this one, your battery and alternator are both suspect. To check this out you would need a ameter, do you have one? Strange how it will start after a short time and then die.

 

[Hibbo]

Stick a voltmeter across the battery, should read just over 12v. Start the car and it should rise a bit, rev the engine and it should go up to 13.8v.

Would be a good idea to leave it running and rev it up and down whilst watching the meter. You could even connect the meter to the snout lighter socket and go for a spin

 

[Ultymate]

From what you have posted, and im still pondering this one, your battery and alternator are both suspect. To check this out you would need a ameter, do you have one? Strange how it will start after a short time and then die.

Eric all discharged batteries tend to recover after a slight recovery period and usually not always indicates the battery's ok I would suspect the alternator but wise to check out both for sure:? Voltmeter more use than ammeter

 

[eric242340]

Eric all discharged batteries tend to recover after a slight recovery period and usually not always indicates the battery's ok I would suspect the alternator but wise to check out both for sure:? Voltmeter more use than ammeter

Recover enough to start the engine and then die? Anyway ill wait to see the end of this one, its very interesting. Anyone got new ideas on this and I hope you will take the cars age into account.

 

[television]

This one should be the ignition switch, the battery and alternator do not behave like this.

You are losing the electrics, when things start stoping all different its normally the ignition switch, mine went the same way on my 129 and same switch.

malcolm

 

[eric242340]

This one should be the ignition switch, the battery and alternator do not behave like this.

You are losing the electrics, when things start stoping all different its normally the ignition switch, mine went the same way on my 129 and same switch.

malcolm

That would make more sense on the start stop bit at least.

 

[wireman]

There are 3 kinds of electrical fault shorts opens and leakage.
Loss of applied power is caused by open circuits which could be caused by fuses failing (due to shorts or leakage) or by a bad switch or wiring connection. Which wire and which connection are the questions that your auto electrician has to spend hours finding out where they are before you get the answer.

If you cant find a wire or switch fault it could be the central wiring unit associated with the fuse box, any damp inside this will result in all sorts of strange behavior. Not closing and sealing the fuse and relay compartment covers will allow damp into this area and it will cause trouble.

As to a cure, short of replacement there is not much you can do to this item without carving it open to look for water damage and corrosion.

Your indicator fuse failiure could be due to a short anywhere in that circuit from the lights themselves and their wires to that there central unit.

 

[television]

There are 3 kinds of electrical fault shorts opens and leakage.
Loss of applied power is caused by open circuits which could be caused by fuses failing (due to shorts or leakage) or by a bad switch or wiring connection. Which wire and which connection are the questions that your auto electrician has to spend hours finding out where they are before you get the answer.

If you cant find a wire or switch fault it could be the central wiring unit associated with the fuse box, any damp inside this will result in all sorts of strange behavior. Not closing and sealing the fuse and relay compartment covers will allow damp into this area and it will cause trouble.

As to a cure, short of replacement there is not much you can do to this item without carving it open to look for water damage and corrosion.

Your indicator fuse failiure could be due to a short anywhere in that circuit from the lights themselves and their wires to that there central unit.

These things are in groups.
If the only things that fail are items that run in the key 2 then it does make it simple to find and the ignition switch is one of them,the most common.

When I get a fault with several circuits that shut down,once you have found the common supply, that the only place where you need look, as the faults are not going to be individual.

Malcolm

 

[eric242340]

These things are in groups.
If the only things that fail are items that run in the key 2 then it does make it simple to find and the ignition switch is one of them,the most common.

When I get a fault with several circuits that shut down,once you have found the common supply, that the only place where you need look, as the faults are not going to be individual.

Malcolm

malcolm could you clarify this, i did not understand.

 

[television]

Its all down to basics, if the lights were intermitant there would be no point in looking anywhere other than the lighting circuit.

With this fault,what do they have in common,

The Radio
Wipers
Ignition
blinkers
In some cases windows
All of the above items are fed by the ignition switch, so if all the above items are playing up how simple it is to put a meter on the switch.

In other word though the items in the above list are all fused,the chances of them all going intermitantly wrong is almost nil.

Malcolm

 

[wireman]

It could easily be the switch and since it gets operated regularly may be prone to wearing out. This is obviously the first place to check and test.
I would not be in the least suprised if the switch was to blame.

However the feed that SW pos'n 2 provides goes to many items and the connection at which this supply is split up and distributed to these items almost certainly will not be at the back of the switch, it will be somewhere (electricaly) near the fuses for the circuits which rely on pos'n 2 probably in the central box.

I mention the central box because I have had problems with these.
The box has wiring harnesses from each major system on the vehicle (ie Ignition switch, combination switch, lighting switch, wash/wipe system front lights, rear lights etc etc) each one plugs into the box seperately.
The problems I have seen have all been caused by water ingress to the central box and have been sorted out by getting another from a similar vehicle in a breakers yard for £10 and £15 a go.

 

[jibcl500]

Yes good one malcolm, ignition switch, Citroen are the same and Porsche 911 have the same problems when the switch fails, took me 4 weeks to find out my 911 was causing so many problems, windows going up and down when Im not there, sunroof opening, cuting out restarting fine etc etc.

But its not your battery!!!!
jib

 

[television]

We all learn something new when it comes to car electrics,when I first joined the forum in Nov05 there were loads of switch problems, more on the 129s as it is the same switch as the 124 but with more loading onto it.

As wireman says he has found problems else where ,who knows. I got my info from a long debate on one of the USA forums where it went into 30 pages and having it go on my own car,the previous owner had changed the expensive N10 relay to no available. Some folk in the States open them up and adjust the contacts with 100% success rate.

aways work out though what is the common link as there is little point in looking at the tail lamps when you have a faulty headlamp.

Malcolm