The Starter Motor Relay Mod - Gone Wrong!

[SkyQuake 70 1 Cars]

Dear All,

 

I've had the starter motor clicking problem getting gradually worse for quite a while now. As with the other threads describing this, the key would turn, you'd hear a click from under the bonnet somewhere, and nothing would happen. Then, often if you keep turning the key over and over, eventually the starter would kick into life and everything would be good. Over the last couple of weeks this has gotten so bad that unless the battery was literally full (or on the charger), then no starting at all!

 

So, I decided to do a little rewiring work in the engine bay, and also add the relay booster circuit which is described in several of the other threads. I took the opportunity to do a few things at once, including new starter motor, new alternator, completely replace everything after the brown multiplug (previously replaced with superseals), and add the relay.

 

The relay circuit uses the starter feed from ignition, to energize a relay, before going to earth. The switched circuit of the relay goes from the large permanent live on the starter motor, through the relay and back to the solenoid start terminal which the starter feed would originally have been connected to, as shown in the below picture. Is this correct?

 

 

Testing this on the bench, it seemed to work perfectly. Starter would come on, and stop immediately on removal of the signal feed to the relay.

 

I then fitted it to the vehicle, and reassembled everything. When I came to start up for the first time, she fired immediately. Almost like she was on a hair trigger! Which I was delighted with, up until I noticed the engine noise was very different. I immediately switched off, and after the engine had stopped I could hear the starter winding down. i.e. the starter was remaining engaged (and powered) even though the ignition was not in the starting position. I tried starting several times, always with the same effect.

 

So I've neatly gone from no starter at all, to a starter which won't turn off! Great.

 

Does anyone have any ideas of what I've done wrong here? I've done quite a bit of work around the front end, so my relay mod might not be the only possible cause. I did notice that the starter is very twitchy on the key, and kicks in immediately if you so much as tickle the key past the ignition on position. Therefore, I was wondering if the ignition barrel might be making partial contact in ignition on, which isn't enough to cause a problem without the relay, but now is enough to be relevant? If that were the case you'd expect it to be permanently on whenever you've moved the key into the on position (but not as far as start).

 

Any suggestions would be gratefully received! Many thanks,

 

Mike

 

 

 

 

 

 

 

[Anthony 1,003]

Been there, done that, got the t-shirt.... and a bit of head scratching later worked out what was wrong.

 

What you've done should theoretically work, and would do, had it not been for a bizarre bit of wiring that Peugeot did.

 

For some reason, they earth the SAD heater circuit through the starter solenoid, which under normal conditions causes no problems at all as there's insufficient current to engage the solenoid. However, put a relay on the circuit where you have, and the small amount of current being earthed by the SAD is sufficient to keep the relay engaged and thus the starter spinning.

 

If you unplug the SAD, the starter will work correctly.... but the idle will be silly high for ages after the engine warms up as the heater circuit in the SAD won't work and thus it'll remain open.

 

What you need to do is one of two things - either modify the SAD wiring so that it earths to ground as you'd expect it to, or place the starter relay further upstream inside the car so that the SAD return is on the output side of the relay, not the input. I've done both in the past now and both work just fine.

[SkyQuake 70 1 Cars]

Hi Anthony,

 

Firstly, thank you. I could genuinely have been searching for that for a year or so and still never found the cause! Honestly, it would never have occurred to me that they'd do something so illogical, especially when the SAD is positioned almost immediately next to the gear box earth!

 

So, just to check, when you open up the engine loom, and follow the starter trigger line back from the starter motor, about half way to the bulkhead (somewhere just before the ignition module I think) there are two smaller light blue wires spliced into the starter trigger wire. I have no idea what these are for; are these the ones you mean? They come from the bulkhead side though, not the direction of the SAD.

 

Do I need to cut these and run them to earth from this point, or can I simply cut one of the two wires at the SAD connector itself and run that to ground?

 

Many thanks again for your help. You've saved me weeks of fault finding!

[ScoobyJawa 23]

Happened to me too! I did as Anthony said with the wiring further upstream and it's worked faultlessly since!

[Leet205 48]

I need to do this mod as well, Where is the best place to take the starter solenoid wire from?

[Anthony 1,003]

On my car I ended up putting the relay inside the cabin between the fusebox and the underdash brown multiplugs.

 

Cut the blue starter solenoid wire (#46) and use the side from the glovebox to trigger the relay, and the side going to the brown multiplugs on the output side of the relay. You'll need to add an earth to the other side of the trigger, and a high current feed to power up the starter when the relay is energised.

 

Obviously you need good engine bay wiring for this to work, but on my car that wasn't a problem - the brown plug by the gearbox had long since gone and a good wire added for the starter.

 

I can't remember exactly where in the loom the SAD wiring joins the starter now as this was a few years ago I found it - I seem to remember stripping the loom back and tracing the wire back, cutting it and earthing it. There is also a starter solenoid feed that goes to the tachymetric relay, which might be the one heading in the direction of the bulkhead you mention.

[ScoobyJawa 23]

Heres my old thread on the subject if it helps:

 

http://forum.205gtidrivers.com/index.php?showtopic=145397