John Vine Posted May 10, 2017 Share Posted May 10, 2017 This resistor hangs down under the dash between the ignition switch and the steering column:It carries these markings:68R 5% MH OG (the "OG" is indistinct).The Assembly Guide appears to know it as "A":The reason I'm asking is that it gets quite hot (too hot to hold for any length of time), and I'm wondering whether that's normal?JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 10, 2017 Member Share Posted May 10, 2017 Have you spotted there's a similar one in the diagram for the speedometer? That made me wonder if they were something to do with LED instrument lights. But the two resistors have very different resistance...Does it get hot when the side lights are off?I haven't found 177 or 178 anywhere else in the chassis or engine harness schematics so far.Jonathan Link to comment Share on other sites More sharing options...
Ian B Posted May 10, 2017 Share Posted May 10, 2017 That type of resistor (wirewound ceramic coated) is designed to cope with getting hot so is often used as a limiting or load dump resistor.No idea why it's needed in that particular circuit (haven't followed it through in detail) but I wouldn't worry about it getting hot. Just try to ensure it's not touching other plastic stuff. Link to comment Share on other sites More sharing options...
John Vine Posted May 10, 2017 Author Share Posted May 10, 2017 ...but I wouldn't worry about it getting hot. Just try to ensure it's not touching other plastic stuff.Good point -- like the bunch of wires alongside! Thanks for the advice.Have you spotted there's a similar one in the diagram for the speedometer?I have indeed, Jonathan, but I'm equally in the dark.Does it get hot when the side lights are off?Oh yes. It gets hot as soon as I turn on the ignition, and with nothing else operating. I've emailed Tony in Parts to see if he can advise. In the meantime, I googled RS199-8829 and found this. It seems from the spec that getting hot is normal.JV Link to comment Share on other sites More sharing options...
revilla Posted May 10, 2017 Share Posted May 10, 2017 Alternator exciter / warning feed? I've noticed the LED in my speedo only feeds about 4mA to the alternator and I've seen a few cars where it's just not enough to get it going reliably. I've been tempted to fit a parallel resistor myself to mimic the current feed from a filament lamp. Is that what they have done on recent cars? Link to comment Share on other sites More sharing options...
revilla Posted May 10, 2017 Share Posted May 10, 2017 Does it cool down again once the engine is running? Link to comment Share on other sites More sharing options...
John Vine Posted May 10, 2017 Author Share Posted May 10, 2017 Does it cool down again once the engine is running?Good question, I haven't yet tried starting the car but will check tomorrow....LED in my speedo...Do you mean the red zig-zag in the tacho? I don't know whether mine is an LED or a filament bulb,...LED instrument lights...On my car (2008), these lights are good old-school filament bulbs. JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 11, 2017 Member Share Posted May 11, 2017 What colour are the wires?Alternator exciter / warning feed?I can't see anything matching on the engine harness. If the alternator is the sort that doesn't have (or need) a separate exciter termnal then where else in the circuit would a resistor work?And why are there two of different sizes? (And does the solver win several prizes?)Jonathan Link to comment Share on other sites More sharing options...
ChrisC Posted May 11, 2017 Share Posted May 11, 2017 Sorry miss posted - Resistor "SEE A" has a different purpose on my car - it's connected to the speedo. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 11, 2017 Member Share Posted May 11, 2017 That was interesting (and would be very helpful on the site somewhere)... and there is another resistor on the speedo in the diagram.John: how is your speedo driven?Jonathan Link to comment Share on other sites More sharing options...
ChrisC Posted May 11, 2017 Share Posted May 11, 2017 Mine is installed because the speedo sensor type and the sensor are miss matched. PNP vs NPN. I did a tone of investigation into this when my car failed IVA due to the speedo. Link to comment Share on other sites More sharing options...
John Vine Posted May 11, 2017 Author Share Posted May 11, 2017 Does it cool down again once the engine is running?It does indeed. You're a clever fellow, Andrew!I heard back from Tony. He said it's supposed to get hot, and its purpose is to prevent the charge warning light from illuminating -- presumably once the engine has started (he didn't say).John: how is your speedo driven?From the sensor + toothed ring on the RHS driveshaft.JV Link to comment Share on other sites More sharing options...
revilla Posted May 11, 2017 Share Posted May 11, 2017 I guess it is in parallel with the charge warning light which is probably an LED. So it will pass current when the engine is not running to excite the alternator and when the engine is running, any small current still being drawn by the alternator will not be enough to drop enough voltage across the resistor to produce the forward voltage required by the LED, stopping it from glowing dimly. Link to comment Share on other sites More sharing options...
micksmetafors Posted May 11, 2017 Share Posted May 11, 2017 Sorry to hijack this thread but I have had an intermittent issue with my Sigma car (2007) since I've had it. The problem manifests itself as very poor light throttle running with a lot of misfiring and kangerooing. This starts once the engine is warmed up after 3-4 miles. Sometimes turning it off and on again cures it. When I had it mapped at T&R they found that the alternator required the engine to be fast idled for 30 seconds to get the alternator to kick in. This often works but not always. I do wonder if the resistor mentioned is causing the problem. From cold the car needs to be caught on the throttle to run and won't idle until the 30 seconds or so are up. Apparently the engine needs to complete 600 revs before the alternator gets going.Any ideas would be very welcomed.Cheers,Steve Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 11, 2017 Member Share Posted May 11, 2017 What sort of alternator is it? What's the battery voltage while it's not working properly? Does it charge fine once it's going?Jooathan Link to comment Share on other sites More sharing options...
micksmetafors Posted May 12, 2017 Share Posted May 12, 2017 The standard alternator supplied by Ford.Never been able to check it whilst not working as the revs have to be kept up manually, one to have ago at.It charges absolutely fine once up and running.I am hoping that Steve Greenald will be over our way sometime soon to have a look at the settings on the ECU. Yes it is a locked one.Thanks for your response.Cheers, Steve Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 12, 2017 Member Share Posted May 12, 2017 Steve: is it possible that you have either: An LED charge warning lamp and a duff resistor, or An LED charge warning lamp and no resistor where there used to be an incandescant? What does the light do when: You turn on the ignition? It's running poorly? It's running well?Do you have a multimeter?Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 12, 2017 Member Share Posted May 12, 2017 I guess it is in parallel with the charge warning light which is probably an LED. So it will pass current when the engine is not running to excite the alternator and when the engine is running, any small current still being drawn by the alternator will not be enough to drop enough voltage across the resistor to produce the forward voltage required by the LED, stopping it from glowing dimly.Well done.Miraculously, and as usual, the diagram makes sense immediately and after the answer is known. Sort of.Tacho: The resistor has a wire labelled 177. There's a two-way something labelled G 171, NY 152. NY is the traditional colour for charge warning light. There's NY 177 on the tacho connector. There's NY 152 on the dash side of the main connector which comes out at NY 62 on the engine side. There's NY 62 and at the alternator. The alternator is of a type that doesn't have a separate exciter.Speedo: Similarly with YB 157, YB 178, YB 156, YB 54, and YB 155 on the vehicle speed sensor circuit of the chassis harness. But also pin 27 of the PCM. Does the resistor in this circuit then modulate the speed signal in some way?I've written those as statements rather than questions to make it easier to read. Please check. All corrections welcome.Jonathan Link to comment Share on other sites More sharing options...
micksmetafors Posted May 12, 2017 Share Posted May 12, 2017 On my Sigma car which was converted to 140 spec a few years ago there is no visible ignition/charge light. Only, main beam and left/right indicator led lights in the tacho. Is it necessary for there to be a charge light in order to get the alternator fired up? There is the normal Toad immobiliser lamp in the dashboard.The car did its usual trick today, 4 miles up the road it starts misbehaving. Stop, turn it off, restart and it is good as gold.Any further comments welcome before I make a pilgrimage to Essex. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 12, 2017 Member Share Posted May 12, 2017 Is it necessary for there to be a charge light in order to get the alternator fired up?Most of ours seem to use the warning light circuit as the exciter circuit. But there are other designs....I'd rig a warning light circuit with an incandescant lamp as a test and see if it makes any difference.What sort of starter do you have and how many wires attached to which terminal, what colour and how thick?JonathanPS: Would you like the light to be resurrected anyway? Link to comment Share on other sites More sharing options...
micksmetafors Posted May 12, 2017 Share Posted May 12, 2017 Thanks Jonathan,I think a warning light would be beneficial, this is the first car I've had without one.I'll have a look at the items you've suggested. What would we do with our time if it wasn't for these little gems?Steve Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now