Bosch Starter Relay replacement on Renix

OK, i've been searching.... and searching with no luck.

The jeep wont crank...the starter relay clicks once when i try...it will start if i connect the solenoid wire directly to the battery. So, im not sure what the problem is other than the power isn't making it through the starter relay.

This is on a 5-speed '88 renix

What is the PN# for the BOSCH replacement relay that can be installed to circumvent the stock unit? I've heard talk of a bosch relay...but no PN#

THanks

A standard Bosch/Hela relay may be used, I just don't remember how I wired it up, and it's just too damn hot for me to go look right now. I've been meaning to write that up for a while...

Why did I do it? Because one summer, a few years ago, I went through a rast of start relays - probably four in three months. They'd hang on just long enough to show that they DID work - right out of the box - but they'd fail in a couple weeks or so. No-one knew why, and I'd even asked the service advisors and techs at the local dealership (just down the street,) since I was out of ideas.

I put in a relay socket and a Bosch relay that came out of my 87XJ (and was original there...) and haven't had a spot of trouble since.

Why do I approve of the mod?

OEMR RENIX Start Relay - OEMR Only, $40.
Bosch "Start" Relay - available anywhere, <$10.

"IBM Presents? You make the call..."

5-90

thank you 5-90,

so, the Bosch unit is OEM jeep, but available after market for cheap. so can i just ask for a 87 jeep XJ starter relay and wire it in?

It seems as though on my '88 there's the main power, a wire that goes to the starter solenoid, a wire that comes from the ignition to trigger, a ground wire, and another wire which i dont know...

jjvande said:

thank you 5-90,

so, the Bosch unit is OEM jeep, but available after market for cheap. so can i just ask for a 87 jeep XJ starter relay and wire it in?

It seems as though on my '88 there's the main power, a wire that goes to the starter solenoid, a wire that comes from the ignition to trigger, a ground wire, and another wire which i dont know...

Click to expand...

Not quite. You can ask for pretty much ANY OTHER RELAY for the 87-90, and that will get you a standard Bosch unit, or just go to your local and ask for a replacement for a Hella lighting kit (which also uses Bosch relays) and go that way. If you ask for a start relay for an 87-90XJ, you're going to get another metal can...

You can either terminate the wiring for the Bosch relay using .250" "Spade" connectors, or just get a pre-wired socket with 8" tails (Borg-Warner makes one, you should be able to get it for about five bucks) and run that in. Advantage to the latter? You don't have to "re-sort" the wiring if you ever do change the relay (and they're cheap enough that you should keep a couple on hand for projects anyhow...)

Bosch relays can be had at local parts houses, or you can get them online for rather less dollars and keep a stock on hand (I typically order them by the dozen - since I use them in most projects as well, to take the load off the switch and "shorten" the power path. Relays are nice - standard relays are REALLY nice! I think I paid about $3 each for my last batch, ordered in bulk.)

I think the HO models used a Bosch relay in the PDC for a start relay - can anyone confirm?

5-90

ok, i understand now. Thanks.

so i could use the extra little blue relay that i have like the one's right next to my metal can in im '88? what is the 5th connection on the stock starter relay that i dont know?

I'm thinking that the 4 terminals are standard relay terminals... and the stud is just to connect power to the other relays and to the alternator?

There are two types of Bosch 30A relay (the little 1" cubes) that you're likely to run into....

SPDT - Single Pole, Double Throw. This is commonly referred to as a "changeover" relay (since it can switch a single circuit to one of two options,) but it's also used as an "on-off" relay - you just don't use the odd terminal.

DPST - Double Pole, Single Throw. Used to turn two circuits ON or OFF at the same time, and is typically used when a paired something needs to be tunred on (I use them for lighting.) Can also be used as an "on-off" relay by not using the odd terminal, but they're a little less common and cost just a touch more.

5-90

if I may interject in this thread. I had to fix my junk in NC 700 miles from home.
Goto autozone/advance whatever "chain" store you have. Find a 4 pin ligh harness relay, it will be over in the elctrical section, near the fog lamps for ricers.
My 87 has two green wires, one energizes when you turn the key, and one goes to the starter solenoid.
I wired the relay to the positive terminal attached to the starter post with a 15A fuse. Took the green wire that enrgzied to terminal 85, and grounded 86 to the fender. Put the green wire that went to the starter on 87 , 30 is the terminal that goes to the start relay post.
That's it, I securd it's mounting tab to the fender in the empty space betwwen the wiring rats nest and the battery.
Now I can use a replacement relay if it dies, like it did on the trail, and not have to start the truck with a jumper wire or screwdriver.
It will eventualy be replaced by a grafted in HO PDC, but it functions just fine.

I think i'll do that...

from looking at my chiltons manual...there is the orange and black wire that also plugs in...this goes to energize the fuel pump when the relay also sends power to the solenoid...when cranking. the black goes to ground on the MT, one green for trigger, and one green to the solenoid. sounds like i better be sure the orange and black wire is connected to the new relay where the solenoid wire is to maintain the connection to the fuel pump...

yeah, mine doesn't have that because I don't have a fuel pump ballast resistor.

ok, problem fixed.

went to like 4 auto parts stores late sunday night...only one was open, and vaautozone didnt have any relays!

all it took was a little looking around under the hood and i found an extra one from an old air horn installation. tested it to see if it worked and it did. wired it up and nothing...

triggered it from a direct jumper to the battery and the jeep started...this made me think that perhaps the trigger wire from the ignition was suspect. removed the horn relay and reconnected everything back to stock.

the weird part is that the stock relay is clicking... you would think it's working if it's clicking...but no!

traced back the ignition trigger wire to up under the dash and whoopie...found that an old allarm installation had spliced this wire to run its own relay...but this one was hooked up all weird with a resistor... maybe part of the ignition interrupt? anyway... i removed this relay and reconnected the spliced wire and everything works just fine now. I'm not sure what changed cause i havn't had that allarm in there for a long time and it's worked just fine in the past. It seems like the trigger wire was just low on voltage...or couldnt keep the stock relay in the triggered position with this other relay in the mix.

i will keep the horn relay wired in so i can switch real fast if the stock one goes out on the trail.

Looks like a rewiring project is in order to get all the relays in order and so that i can easily replace them.

THanks

further investigation found that when the ignition was in the start position, the allarm relay would trigger, providing a lower level voltage to the allarm unit. I took a look at the end of the allarm harnes that was laying in the engine bay and found that the plug had melted and shorted the wires that came out of the relay...so basically...when i tried to start the jeep...this short with the resistor in it was sucking out voltage from the starter relay trigger circuit.