Mooching around eBay and saw this 8v engine on offer with what appears to be a non-standard sensor attached. Just curious as to what it may be for... as simple as somewhere to bolt one (for what?) because of the existing vacant threaded hole there or is it to perhaps measure cylinder head temperature (would that even work saying as it's external to the casting?), just thoughts.
I've seen them before, but not sure where or why lol. Does look like a thermo-time switch, if it weren't an injection head I'd say it was for the cold start on the carb....maybe a mix and match carb/injection car/engine combo. Unfortunately I'm not a great font of knowledge on std and oem stuff as I don't take much interest in that, just competition and racing.
Yes its a temp thermo sensor,they can be mounted in differant positions on the head dependant on engine ,mine is abf running k-jet so mounted front right on rocker cover ,unsure of how works but would presume it is a by-metal,mine has a single back wire that heads to the engine loom from what I can see. I have a spare and its rated @ 140C max but not sure if thats for all of them,sure rubjonny will chime in as he will know the function in the system ,cheers.
it's a temperature switch. when temperature in engine compartment of parking car exceeds certain temperature (usualy 90-100°C, it's stamped on switch), radiator fan is switched on, to remove the heat from under bonnet. this prevents fuel in fuel lines from boiling, and improves hot starts..
Ah... So it's possible the engine had been converted to run carbs, with the temp. sensor an add on because of that. We think the EV earmarked for my MK1 was the same, it had a penny in each of the injector ports to blank them off, secured by the brass inserts. Took a bit of hunting but found the auction again.
some kjet engines do have the rad fan after-run system fitted, not sure about the whys and whens though. its wired to a relay on headlight loom above fusebox 220, and you have an extra red/white wire plugged into the rad fan wiring which is what triggers the fan
Interesting... does look to be a non-homemade bracket and should be there. So in principle it trys to dissipate heat after the engines shut down if the temperature around the fuel lines is too great. Will have to look into it further, may potentially be a retro fit improvement. Found this on Vortex, someone asking a similar question, only their sensor is in a slightly different place, plus on a RD engine. The RD has CIS-E and not the basic CIS of the EV engine, does CIS-E not have a Control Pressure Regulator (or at least not have it fitted here) and that allows the previously unknown temp. sensor to be fitted where it is? The EV has a CPR, hence it's sensor having to be elsewhere?
yeah main purpose would be to stop fuel vaporising in the fuel lines I expect, but isnt really an issue as most MK2 here dont have one of these and not something you hear about being a problem... IIRC someone mentioned something to me about it being there to help prevent exhaust manifold cracking, but take with grain of salt as its 'man down the pub said so' level of information I recon
Found this image which appears to show a similar sensor / bracket (a UK car judging by the registration, but not a given I suppose) and in the same place as the one shown in the first post. Hard to see things clearly, so have tried to zoom in a little. There's what seems to be a wire from the sensor running back up to the main loom / bulk head area. Also had a trawl through 7Zap but with no success. Did notice however they make a distinction between radiator sensors / pre- installed looms and fan types intended for vehicles that will be towing trailors / used in warm climates or prepared for aircon... maybe some connection?
to me that suggests either cars with towbar got it, or those with run-on. but if so it doesnt say when run-on was specified for cars without towing
Spot on... mystery solved then! With the solitary exception of the 1.3 Catalyst engine, 191 919 521 B cross references to Golfs / Jettas / Sciroccos / Caddys that are 1.8's only, injection or otherwise. The bracket's (026 906 287 F) still available, as is the sensor -
I know my car doesn't have this fitted but wonder if it should. I may try earthing the black wire spade terminal that is floatinh by the Inlet Manifold and see if it brings the fan on. Hmmm
if the wire is there and your headlight loom is original then you should have it, but if you haven't noticed any hot start issues over the years then you are fine without. however I understand if you want to add it in anyway because it 'should' have it
A bit of a tidy up to the original post... The sensor and it's specs. seem to be pretty common ones. Most of the usual suspects make their own versions and they're generally quite cheap, so I'm guessing it's maybe something that's used for a few other applications as well. By chance found a new VW one on eBay at the first search, plus it was half the price of a modern copy, no brainer. The bracket, as said earlier, is still available via VW Classic Parts though did find a few second hand ones on offer for the same or more money, bizarre! Yes, could've made one up, but for all it cost doubt it'd saved me very much. If you're thinking of getting a bracket be aware the piccie I posted of the one at the front of an RD engine is different and has it's own profile so there's at least 2x versions out there depending on fixing position. RJ said somewhere about there needing to be 3x wires into the fan? By chance I'd got a new fan last year, the existing one was presumably the original and the bearings were shot, wobbled all over the place. Remember at the time I couldn't get another 2 pin one, all the new ones were listed as either having 3 pins or made no reference at all. Because of that just picked the cheapest Autodoc had (a Ridex own brand) at the time. Turned out to be a sturdy, well made thing and fitted like a glove. Had a look today and have realised you can get fans from single speed with low wattages (60'ish) through to twin speeds that rise incrementally through 120 / 200'ish watts up to 150 /250'ish watts. The single speeds are for cars with neither towbars / air-con / not forwarm climates, the twins work their way up from tow bar / no air-con to finally having all three. Pure luck the Ridex came in mid field at 120 / 200 (cars with a towbar). It's looking more like the sensor came in with the first MK2's on Kjet / 1800's wasn't on any MK1's. My MK1s loom is in a box somewhere so can't check but based on the original fan being 2x pin have to assume there's no factory provision to fit the sensor. As electrics aren't my thing I'm maybe over simplifying it, and bearing in mind I'll not have the head-lamp loom wire / relay, would it be a reasonably straight forward job to include those separately into the electrics?
Rubjonny is probably the one to answer this with a wiring diagram. My mk2 has a black cable and spade terminal that come out of the loom by the coil which is long enough to reach the sensor location. And there is another wire spare by the N/S headlight which I believe is for this system. But I don't know anything else I don't know why or if it was removed, but I will have a look at the fan tomorrow
Sounds like you're good to go once you've a sensor (and fuse box relay too perhaps?). As RJ says, it's a fix to a problem that probably seldom occurs with standard UK cars, it's if you've air-con or tow here that it'll possibly come into play. With me putting in the bigger engine there might turn out to be some advantage, but it's such an inexpensive, easily reversed tweak I reckon it's worth experimenting even there's not.
Interesting, I’ve seen that sensor before and wondered what it’s for as I’ve seen it pictured in EV engines and mine is an EV engine that doesn’t have it. Mine does however after-run the fan if it feels the need. Not sure where the sensor on mine might be? I’ll have a look next time I’m under the bonnet..
Ignoring the unknown sensor for a moment, does the fan run on not work via the coolant thermo switch which you'll already have? Plucked a random application from 7Zap, a 1986 MK2 / 1.8 EV, just as an example to work out what's, what. There's a choice of two thermo switches, one for the single speed fan (two pin) and one for the twin speed fans (three pin). Concentrating on the twin speed switch, it works at 95-84C/102-91C. Back to the unknown sensor', its marked 'Max. 140C', but there's also '110C' marked elsewhere, would that be the temp. it'd kick in at? Would that mean the 'coolant' activated fan run on kicks in at a max. of 102C, whereas the fuel line area temp. needs to exceed 110C before the unknown sensor would kick in? As they're independant of one another is it potentially trying to combat situations where the parking temp. at the fuel lines can be 110C or above, yet the coolant temp. is below a max. of 102C otherwise the thermo switch'd be enough on it's own?
you can use this with either 2 or 3 pin fans, what you need is the extra wire near the 2 pin main power spade plug on the fan loom. I expect thats what you were thinking of? Its spliced inline with the red/white between thermoswitch and fan for 1st speed for a 3 pin fan, or for a 2 pin fan its spliced inline with the only wire from switch to fan the rest of the wiring is in the headlight loom, there is a wire for your thermoswitch which pokes out near the coil, and theres a spade near the main 2 pin power/earth plug for the fan run on power these both run back to a relay holder above the fusebox with a #220 relay in it
Jumping the gun a bit but resurrected the wiring loom today, it'll need a week (or three!) to unravel and make head or tail of it all. What I did find almost immediately was the sub-loom pictured below for the radiator thermo-switch (all 2x pin). Those connections going into the thermo-switch itself don't look right, surely it'd have been a 2x pin / booted item? That's how it came off the car, though whether it's right or not is another thing altogether. Remember I'm a MK1, will I have some of the connectors / wire colours that you describe, very little seems to match? Wish I could make good use of your schematic, likely answer all my questions but it goes way over my head unfortunately. Don't be going into any detail just yet, I'm very, very far away from looking at the electrics... I've got a horrible feeling I'm fooked as it's in a right mess, so save yourself for lots of questions sometime in the future.
