924Board.org

Beartooth · Joined: 05 Apr 2022 Posts: 280 Location: Roberts, MT

Has it been a year and a half? Yikes! The bad news, unsurprisingly, is not much has changed. The good news is, it's been an enjoyable runabout and back-road blaster, and the shop is complete enough that it's parked inside now (usually, depending on other projects and finish work on the shop). The work on the shop definitely falls in the "eat your vegetables first" kind of thing: it's getting there, but I've still got a couple weeks of work before it's sorted. Then I stumbled across a Jaaaag that was too good a deal to pass up. It's an '85 XJ-S, and it's basically rust-free with no signs of accidents and able to move under its own power, but it needs a lot of mechanical attention. Given the prices I'm seeing, my reward for fixing it up will probably be enjoying it for a while until I can find a good long-term home for it. It's one of those cars that's one clueless owner/mechanic away from the wrecker, and that'd be a real shame for such a car. Hard to believe a near-perfect example is worth maybe $20k and a typical driver would do well to hit $5k; it's just so much more car than that, to my eye.

Anyway, on to the 931. I drove it on and off through last summer, but later on, the fan motor decided to eat itself. It might have kept going quite a while if I'd just kept oiling it, but that's way too much of a hassle. It started making noises, then sounded like it was binding up, so I just unplugged it and avoided driving it in stop-and-go traffic (there were a couple times when it first failed where I had to shut it off coasting to a light, then hope I got moving enough to cool it down between lights).

Since I couldn't immediately find the Toyota fan people talk about, I decided to go back to the 12" universal fan I had sitting around. The first time I tried to mount it, I tried to do so with the mounting bolts aligned with the holes on the radiator, but immediately found that the air box wouldn't fit that way. Speaking of the air filter assembly, my winter storage "present" was a mouse chewed up a shop towel, built a nest, and left a litter in there... Could be worse: I don't see any signs of the wiring having been hit. Anyway, I had some 1-1/4"x3/16 steel stock, so I cut some brackets and counter-sunk some screw holes for the top so the fan could drop low enough (the top of the fan basically aligns with the top of the radiator now - not counting the eyelets). Hopefully the pictures give a good idea. The bottom was much easier, since the flange of the fan sits below the bottom of the radiator. I painted the brackets just so they wouldn't rust and scrounged some hardware. Nothing pretty, but it's probably something I'll revisit when I get around to rebuilding the engine. Also, I stuck some strips of foam to the bracket where it meets the radiator to keep it from rubbing or vibrating. Probably unnecessary, but who knows. Still to be done is to wire in a relay. Right now it's just wired to the original fan plug, and it feels a lot weaker than when I hot-wired it to a battery. I suspect it's one of several places where the factory wiring is robbing voltage, and any 924 would benefit from a relay wired directly to the battery.

That might be it for a while. After I got the fan in, I drove into town - the first time I've taken it more than a dozen miles from home this year - and filled up with gas with some Techron and Sta-bil. Happily, it's still firing right up (maybe with a little extra cranking the first time I started it this spring). Going off the odometer (180 miles; the gauge is another "need to fix"), I didn't expect it to take much to fill, but it took over 11 gallons! No leaks and nothing weird I've noticed, so hopefully that's just because of occasional runs to warm it up and the cooler weather (last fill was in November). Anyway, I'm holding onto the original shroud and will probably put the Toyota fan in it, or an aftermarket 11" fan. Ideally, I'd drop in an aftermarket fan with a PWM controller, but I think what I've got will work for now (with a relay/wiring upgrade, of course).
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1980 931 diamond in the rough

Beartooth · Joined: 05 Apr 2022 Posts: 280 Location: Roberts, MT

I installed the relay yesterday, and it's a big difference. I used a pretty standard relay (weather sealed though), mounted just under the coolant expansion tank using one of those mounting bolts. I pulled the power supply off the alternator and used the ground just behind the left headlight. I just wired the positive side of the trigger circuit with the supply wire, then ran the negative side to the thermostatic switch on the radiator (obviously grounding the other side of the switch). So far it works just as you'd expect, and as I indicated, it makes a big difference. Before, you couldn't hear the fan at all over the engine; now you can, and it makes a pretty healthy sound with the engine off. This is just an uneducated guess, but it's probably pulling 20-30% harder. It has no issues keeping cool in traffic so far; It'll be interesting to see what it looks like when it gets hotter, but I think it'll cool better than the original setup now, even without the shroud. Degraded wiring might be partly to blame, but I suspect most cars would stand to benefit from a relay in place of the original wiring.
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1980 931 diamond in the rough

Raize · Joined: 18 Sep 2013 Posts: 337 Location: Scotland

I hate how Porsche used tiny wires with a ton of voltage drop for everything.

Beartooth · Joined: 05 Apr 2022 Posts: 280 Location: Roberts, MT

Yeah, I'm surprised at how much wimpier the fan sounded before. I'm wondering how much of a difference relays would make on the headlights; it's tempting to keep adding relays, but it might be wiser to hold off until I rebuild the engine and install a whole relay subpanel to cover the fan, headlights, maybe fuel pump, and I'm sure I could think of more. I suppose they were saving money with the thinner wire, but it seems like a big trade-off to me. I suppose the Germans weren't known for being fanatics about the electricals, but you'd think a premium car would have a bit more premium wiring.
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1980 931 diamond in the rough

924RACR · Posted: Fri May 30, 2025 9:01 pm Post subject:

Beartooth · Joined: 05 Apr 2022 Posts: 280 Location: Roberts, MT

Yeah, I thought of the VW connection, but dismissed it because it was never sold as a VW and would have wiring specific to it. But I suppose there is a good chance the wiring is a vestige and was actually designed and specified by VW. It definitely seems marginal - the volt gauge drops .5 volts when I turn on the headlights, and it took me a couple tries to find a circuit with enough power for the wideband (it'd just keep flashing the warm-up code, I think it wasn't able to get hot enough for the initial calibration). But on the other hand, other than needing a new turn signal switch, fuel pump relay, and some contacts cleaned, it's worked pretty well considering the age and neglect.

I've never had a 6V car, and it seems like ancient history, but then you realize that when the 924 was designed, 6V systems were only 10-15 years in the past. Obviously, I'm about to tread on English soil (figuratively; I've done it, literally, a couple times in the last three years), but so far at least, I haven't found any major gremlins in the XJ-S. I've got a fair way to go on it though...
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1980 931 diamond in the rough