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20th September 2016, 07:25 | #21 |
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Hi Simon, new brushes it will be. I was more concerned about the condition of the commutator but close look last night shows it to be in good condition, a quick clean with the comm cleaner stick is all that's needed. Bearings good as well.
What's of concern now is that the control box relays do not respond with the demist test. I have 3 working relays and good continuity from the pair of connectors to the control box relays/motor. There is 12 volts down to the control box, black and brown wires. A relay clicks in the under bonnet fuse box, not sure which one, will check. I've checked the fuses. Are any of the relays there part of the demist circuit? John |
20th September 2016, 07:44 | #22 |
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John are you doing Demist test with engine running?
Petrol variants have to be running for cooling and AC demands (apart from an overheat situation of course) Relay 4 near battery is main IGN relay. Relay 5 is cabin blower. Good luck with the rebrushing.......very brave man
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20th September 2016, 07:49 | #23 | |
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Quote:
For security,remove the big 80A fuse powering the motor then connect the tiny blue/red wire (PWM signal) to earth and listen. You must feel the three relays activate successively.(within around 2 seconds) Then,releasing the wire , they must disconnect in reverse order. Of course you can do it with the fuse in place BUT be careful If you earth the grey wire (ATC),only the second speed relay is activated (the yellow one is + 12v) Mike Last edited by FrenchMike; 20th September 2016 at 07:56.. |
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20th September 2016, 08:48 | #24 |
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Mike, the car is a petrol V6 so does not have a PCB in the fan control box.
Jules, if the car was to be used daily then I would be buying one of your fans, but as its only being driven for fun and (very) limited miles I'll give the rebrushing a go. Might still need to buy a fan if it doesn't go well! Tried the demist test with engine on and off, inconclusive with the engine running, fan still on the car so could not hear the relays clicking. If the weather improves later I'll put the control box back on the car, start it and see what happens. I assume it will be OK to do that with the bumper and headlights off? |
20th September 2016, 09:16 | #25 | |
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In your case ,it's simpler ,I think there is one separate command by speed ; so 3 tiny wires that are earthed when needed by the ECU ... |
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20th September 2016, 13:30 | #26 |
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Yes John stuff can be tested with bumper/head lights removed.
But make sure demist is used as dash will read -30C so ATC will think you are in the arctic so no LO settings will work but demist overides everything !! The only sure way to monitor relays with Petrols is with a very small wattage bulb (so as not to damage ECU) or preferably a Voltmeter to see if any voltage going to relay coils. FrenchMike Message for you re PWM's I measured the blue/red signal for an AC command just for those without an oscilloscope. AC on The voltage is approx 6.5v DC (obviously in reality this is a square wave) AC off Voltage is 8.5v
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20th September 2016, 13:31 | #27 | |
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Only the large relay (low speed) will respond to the demist test. Here's a way of testing the circuit: Take off the control box lid. Place your voltmeter between the thin blue wire (on the large relay base) and earth. It should read battery voltage. Now start the engine and press the windscreen demist button. The meter reading should fall to 0v. That shows that the low speed relay is being energised by the ECM and the motor should then run. It probably won't, because one of the low speed brushes has worn out. Simon
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20th September 2016, 15:09 | #28 | |
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Quite possible ,you have measured the mean value : About the ECU ,i don't know the diagram ,i only suppose they are open drains. so we could earth the output without damage Mike |
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20th September 2016, 17:20 | #29 |
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Mike,
Both your oscilloscope traces appear to show an amplitude of about battery voltage (5v per grid square in the vertical direction). Am I right? Simon
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20th September 2016, 18:03 | #30 |
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