The Stovebolt Site Forums The Shop Area The Electrical Bay Relay Quirk?

Yesterday my overdrive ('69 Saginaw/Borg-Warner) decided not to engage. I have it set up with a reminder light when it hits 30mph or so and I couldn't recall whether I was hearing the all too familiar 'click' of the relay.

Today, got out for a drive and the od is working as normal.

My question, is it possible for a Bosch relay to start to fail by working intermittently or is it like the heart muscle 'all or none'?

This form, including the same relay and solenoid has worked without fail for four years, dd/only vehicle.

Any insights folks?

What amperage capacity relay are you using? A 30 amp might be on the ragged edge of too light duty, as the initial current surge of that big solenoid is pretty high before the inductive reactance of the coil kicks in. I'd suggest going to a 60 amp if you decide to replace it. Yes, they can get intermittent when the points start to fail. I'd also suggest connecting an ignition condenser between the solenoid hot terminal and ground to protect the relay points from induced voltage and possible flashover as it engages and disengages.
Jerry

Holy relay Batman! I think the one that has been on there for 4 1/2 years is a 20 amp, and I think it's the same one I had with my previous OD, that means it was on for 10 and maybe 15 years.

Will definitely replace with a 60 amp, thanks. I know I've put that relay (Bosch brand) through a lot of cycles, countless 6-9 hour trips, wow.

Thanks HRL!

They're dirt cheap on Ebay- - - -and even come with the appropriate connector. I usually buy 'em 10 at a time and use them for headlights, fog lights, air horn compressors, etc.
Jerry

I just had an issue with my jeep's electrical system. Worn relays caused me to just empty every pocket of all of the money I could find. The most popular troubleshooting solution was to swap a "less used relay (horn or fog lights)" with the fuel pump and/or the automatic shutdown relay. Continued failure led to the next steps of replacing expensive components... at least I have my new fuel pump installed and I have an extra PCM.

I'm going to wire up relays for my high and low beam headlights. It seems that the wire on most of the connectors that come with the relays are of a lighter gauge than seems appropriate, depending on the purpose. Is it proper to go ahead and solder say, 12 gauge wire to whatever gauge is on the pigtail, or should one jettison that complete section of wire and replace it all the way to the relay itself ?

Do you have fuses installed? If so what amperage? In building wiring 14 ga copper is rated 15amp. 12ga 20 amp and 10 ga 30 amp copper. Around 90C rated insulation. The relay coil should only draw a few milliamps,To Save the light switch. I would buy a relay socket and solder wires to the socket. Soldering a heavier wire to a lighter wire just makes the lighter wire the fuse.

Thanks. That makes sense.
I plan to use fusible links from a common lug on the power wire(s) to the relays.

I don't believe the NEC (codes) apply to autos. The code were written for the insulation around the wire, not the amount of current a wire will handle without melting. For example, a #12 bare wire hung in free air will conduct much more than 20 amps without melting. Another example, and one I have never understood, is the "Spal" radiator fan I have installed in on of my rides. It draws about 15 amps. The wire pigtail supplied from the factory is about a #22 gauge. Another is the output wire from a high output alternator. It's very common to see a #10 or #8 wire. Some output around 90 amps. Go figure?

Buy a 60 amp relay for each headlight beam, and the corresponding connector. A 30 would probably be adequate, but I believe in overkill. The power-carrying wire on the connector will be right for the capacity of the relay. Run a HEAVY wire like a #10 to the area of the radiator core support, then use wires equal to or slightly heavier than the wiring of the relay output to power the headlights. Use one relay for both high beams and another for low, and energize the relays with the dimmer switch output. Have fun!
Jerry

Right on. I was on the right track, but I'll use the heavier relays for the lights. Gives me the wire size I want and just mo betta.

The NEC does not apply to auto's and also anticipates more than one current carrying conductor grouped together. It's a good place to start if you have no other info. You can only go wrong under sizing wiring. 10 AWG is a bigger diameter than 14 AWG. You can also increase the temperature rating of the wire and make the wire Ga size smaller within reason. 60, 90 and 105C are very common insulation ratings. You also want insulation that is oil and gas resistant.

Agree with GWWirth. If you gotta have it, you can get SXL automotive wire good to 125C (257F).

Temporarily replaced relay with a 20/30 and overdrive is again working crisply. I've ordered a dozen 60 amp per HRL'S recommendation and will install a single 60 amp in the place of the 20/30 when they come in.

So for the record the symptom was as if the blocker ring had lost friction and wouldn't engage overdrive and symptom #2, failure/intermittent relay. Cheap and easy solution, thanks for the help.

Worth keeping an extra relay in my on board fix-kit.