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-   -   Can someone please explain to me what the start bridge relay does? (https://rennlist.com/forums/928-forum/731073-can-someone-please-explain-to-me-what-the-start-bridge-relay-does.html)

ledee416 12-11-2012 02:53 PM

Can someone please explain to me what the start bridge relay does?
 
I noticed that they are differently listed for mt and at. what is he deal exactly?

I have been jumping this relay (was like it when I got the car), and was told by PO it was the fuel pump relay in my 1980 US. After having to jump the pump relay in my Euro, I realized that it was not in fact the pump relay, but rather the start bridge. I was just curious as to what it did exactly, and if someone has the numbers off of it so I can find a new one. It doesnt appear as if either ebay or 928 site stocks it by name.

Ducman82 12-11-2012 03:02 PM

the bridge by passes where a relay would be. that relay is so the car will only crank in neutral or park

dr bob 12-11-2012 03:03 PM

The starter relay is used in the automatic cars to allow a neutral safety switch to limit starting to when the selector is in either park or neutral position. In manual transmission cars, with no such safety switch, the jumper is installed between 30 and 87, so that the key switch can directly actuate the starter solenoid.

[fixed terminal numbers per Alan's info below. Thanks!)

Alan 12-11-2012 03:25 PM

Its a standard 87/30 bridge - in this case the relay 30 terminal is actually fed by the starter switch (50)

When there is a relay (AT) - 86 is ignition and 85 goes to the neutral safety switch (relay on when in neutral & ignition on). This config changes in later years so the relay actually decoupled the switching from the switch.

Alan

ledee416 12-11-2012 03:33 PM

as of right now, I have it jumped between 87 and 30. There is no bridge on it, just a wire with flat blade connectors. Do I need to put an actual bridge on there, or can I keep it the way it is? I am wondering if this setup will drain my battery. If it isnt a relay, then I am guessing it wont, but I am not sure.

Alan 12-11-2012 03:39 PM

1 Attachment(s)
A relay bridge looks like this...

Alan

James Bailey 12-11-2012 03:53 PM

bridging or a jumper wire means your car WILL start in gear which can be a big surprise !!!! Not what people expect with an automatic. Be safe you never know who might be starting the car.

Alan 12-11-2012 03:56 PM

Bridge as shown is 928.615.125.00 (for MT)

As Jim said if this is in fact an AT car fix this with a standard Bosch SPST/SPDT relay (any auto store) and whatever else may be needed to fix the neutral safety switch (if needed?)

Alan

ledee416 12-11-2012 04:23 PM

awesome. thanks. It was weird. I was trying to pull the same relay out of my euro. It had no cover on it, and when I squeezed it to pull it out, the car turned over. it was pretty startling. I guess I will go hunting for the standard relay then. just ask for Bosch SPST/SPDT relay?

Alan 12-11-2012 04:41 PM

Either one works just fine: Bosch style SPST or Bosch style SPDT - can be any actual brand.

Note - Always disconnect the battery before doing electrical work on your 928...

Alan

dr bob 12-11-2012 06:14 PM


Originally Posted by ledee416 (Post 10064770)
awesome. thanks. It was weird. I was trying to pull the same relay out of my euro. It had no cover on it, and when I squeezed it to pull it out, the car turned over. it was pretty startling. I guess I will go hunting for the standard relay then. just ask for Bosch SPST/SPDT relay?

^^^^ What Alan said about disconnecting the battery.

The relays seem to be pretty secure in their sockets. It's easy to squeeze a relay cover hard enough to actuate the relay inside, or pull on it hard enough to separate the cover from the base. There's a fancy relay pliers that solves the first problem but still rsisk pulling the cover off. There are more than a couple solutions as always. Mine uses a couple paint can openers with the ends bent over to almost 90. High-dollar Home Depot tools that have what looks like a bent screwdriver end and a looped handle. I just added to the bend so it could fit under the base of the relay. Slide them under on opposite sides, rock a little then pull, and the relay will be out on the carpet in a flash. To avoid that flash, follow Alan's suggestion about disconnecting the battery first, so the metal puller ends don't short the relay pins together.

jbrob007 12-11-2012 07:31 PM

The cool thing about the Home Depot paint can openers flattened out to remove relays is the OTHER end is a bottle opener... perfect for opening that expensive bottle of German beer when the job is done! :)

17prospective buyer 12-11-2012 08:03 PM

So manuals don't even have a clutch switch? That would explain why i can start my 928 without pushing the clutch in. Good to know it's not a PO butcher job.

jbrob007 12-11-2012 08:10 PM

My 86.5 has a clutch switch... What it does exactly I'm not sure. I assume it has something to do with starting the car like blocking out the ignition while in gear. But there is a contact switch activated by the clutch pedal arm when depressed... at least on my car.

Hilton 12-11-2012 08:39 PM


Originally Posted by jbrob007 (Post 10065317)
My 86.5 has a clutch switch... What it does exactly I'm not sure. I assume it has something to do with starting the car like blocking out the ignition while in gear. But there is a contact switch activated by the clutch pedal arm when depressed... at least on my car.

The pressure switch on the clutch pedal is for the cruise control - so you can change gear while cruise is active and the engine won't redline :)

Alan 12-11-2012 08:45 PM

The sole purpose of the switch is to dissengage the cruise during gear changes - then it auto resumes - this features works very well - but is rather important on a manual car, lest the Bwaahh! becometh too much....

Apparently only the drivers of Rogerboxes need to be protected against themselves for inadvertent starter issues...

Alan

James Bailey 12-12-2012 01:50 AM


Originally Posted by Alan (Post 10065413)
Apparently only the drivers of Rogerboxes need to be protected against themselves for inadvertent starter issues...

Alan

I rather like that :)

Landseer 12-12-2012 03:08 AM

3 Attachment(s)
Regarding starter bridge for manual cars: configuration changed for 1982 MY.
That bridge only exists in the CE panel of manual cars, MY 1981 and earlier.
(Alan is picturing a bridge in a late model panel, maybe his 94, for which purpose is a backup light bridge)

Mid year manual cars have a start bridge, but its located in the hatch area.
And, beginning 1982, both auto and manuals have the start relay.
See the first 2 documents below.


The confusion comes in when people with manual cars newer than 1981 go searching for the start bridge so solve a no-turnover issue and find a relay.

Its perpetuated because the manual start bridge is referenced in relay diagrams, including PET and 928specialist site, and has a part number. This co-location infers that the bridge located in CE panel.
But they are talking about two different configurations of bridge.

82-on manual owners should find a relay in the slot. And the bridge is a wire jumper near where tranny harness attaches in hatch area. If automatic, instead of the jumper, there is a shift linkage position switch ensuring car will only start in P or N.

See the third document below.

dprantl 12-12-2012 10:03 AM

I never did understand why this interlock was put into place for "safety". Starting an automatic car in gear is much less dangerous than starting a manual car in gear, with the torque converter not being direct drive with the wheels when stationary.

Dan
'91 928GT S/C :eek: 475hp/460lb.ft

ledee416 12-12-2012 03:05 PM


Originally Posted by dprantl (Post 10066412)
I never did understand why this interlock was put into place for "safety". Starting an automatic car in gear is much less dangerous than starting a manual car in gear, with the torque converter not being direct drive with the wheels when stationary.

Dan
'91 928GT S/C :eek: 475hp/460lb.ft

unless of course someone is standing in front of it :)

PorscheTX928 05-18-2015 02:40 AM

Need a little help with starter bridge issue
 
1 Attachment(s)
First...I have an 82 928 S (manual). From what I have read from the previous posts is that my 928 has both the relay(XIV) and a bridge (somewhere in the spare wheel well). Is this correct?

I ordered the Relay referencing the wiring diagram and part numbers from Porsche International..According to this wiring diagram Relay XIV for 82-84 model years has part no. 92861247300(Bridge for Starter-M/T). I ordered the part but it is not a relay. I have included a picture. I am assuming that this is for the bridge in the sparewheel well.


Ok...I have two questions - 1) What is the part no for the relay that goes in the relay XIV spot? And 2) Can someone point me to a picture or explain where I can find the bridge in the spare wheel well? I dont see it, and have no idea where else it could be.

Thanks.

Alan 05-18-2015 10:46 AM

You can use a standard 53B relay from Roger (etc) for any starter relay (even the early model start DISABLE relays) - or in fact you can use any standard Bosch SPST or SPDT relay (but get a reputable brand).

The bridge goes behind the plastic cover in the spare wheel well - above the battery box and ahead (in the car) of the spare wheel. many have never realized its there until directed to it - there may be a 'felt' like cover over it. You most likely already have a similar bridge installed there.

Alan


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