Roadster 452 blower ground issue - Smart Car Forums
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post #1 of 10 (permalink) Old 07-16-2014, 02:40 AM Thread Starter
 
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Roadster 452 blower ground issue

Greetings,

My blower motor just died suddently. I disassembled and cleaned it. Motor also works with the direct current from the battery. I also replaced the resistor pack with no difference what so ever.

I measured the current from the motor connection and it has quite unusual readings. The wire wich goes to resistor pack is giving +12v on each speed selector settings including the off-position.Assumable ground lead is also giving +12v measured from the battery. The car has the upgraded ground on the battery and it's giving the correct voltages to the radio's din-connector.

If I connect ground directly to motor it starts spinning and also ignores the speed selector settings. Is the motor ground controlled or what is going on?

I'm quite hopeless with the blower motor right now. Any ideas what to do?

Yours
Heikki
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post #2 of 10 (permalink) Old 07-16-2014, 03:01 AM
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Kane at www.Evilution.co.uk might have an answer for you. They have roadsters in the UK. We never got any roadsters in the US. except for one or two units brought in illegally including one at Smart Madness. SMART MADNESS - smart car Parts and Accessories. Those guys might have an answer. Kane certainly will, his site is a pay site but worth the small fee. He has lots of info on all models of smarts. I highly recommend www.Evilution.co.uk hmm, his site is down at the moment but should be back up momentarily. I'm guessing down for servicing. It is five AM here.

Last edited by BB Benz; 07-16-2014 at 11:15 PM.
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post #3 of 10 (permalink) Old 07-16-2014, 07:22 AM
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post #4 of 10 (permalink) Old 07-16-2014, 01:17 PM
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Originally Posted by heikkimus View Post
Greetings,
I measured the current from the motor connection and it has quite unusual readings. The wire wich goes to resistor pack is giving +12v on each speed selector settings including the off-position.Assumable ground lead is also giving +12v measured from the battery. The car has the upgraded ground on the battery and it's giving the correct voltages to the radio's din-connector.

If I connect ground directly to motor it starts spinning and also ignores the speed selector settings. Is the motor ground controlled or what is going on?

I'm quite hopeless with the blower motor right now. Any ideas what to do?

Yours
Heikki
You are getting 12 volts on all the resistor positions because there is no ground connected. With no current flow there is no voltage drop through the resistor segments. The blower motor is supplied 12 volts on one side and the other side of the motor is grounded through the blower resistor and fan switch. The ground for the fan switch is probably internal to the hvac or climate control unit, if you have air conditioning. If you do not have air conditioning I would need to find the correct wiring diagram for your car to see where it is grounded.
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post #5 of 10 (permalink) Old 07-20-2014, 09:05 AM Thread Starter
 
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Originally Posted by Rustedwrench View Post
You are getting 12 volts on all the resistor positions because there is no ground connected. With no current flow there is no voltage drop through the resistor segments. The blower motor is supplied 12 volts on one side and the other side of the motor is grounded through the blower resistor and fan switch. The ground for the fan switch is probably internal to the hvac or climate control unit, if you have air conditioning. If you do not have air conditioning I would need to find the correct wiring diagram for your car to see where it is grounded.
I thought the same. I've the AC.

So should I now disaseble the dashboard and try to figure out the ground for the switch?
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post #6 of 10 (permalink) Old 07-20-2014, 11:38 AM
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I thought the same. I've the AC.

So should I now disaseble the dashboard and try to figure out the ground for the switch?

On a roadster model 452432 or 452434 the ground for the fan switch is a brown wire located under the center of the dash, behind the center stack where the radio and switches are located, on the right side. With your head in the right footwell, look left. It should be on a stud on the metal brace under the dash in line with the right side of the center console. Make sure the connection is clean and tight.
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post #7 of 10 (permalink) Old 07-20-2014, 11:46 AM Thread Starter
 
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I think I've checked it out. It's on the right side by the steering box or something similar.

Am I able to check the grounding of the switch trough the center box? I already stripped everything from there and measured the voltages from the switch and it showed +12V.
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post #8 of 10 (permalink) Old 07-20-2014, 11:49 AM Thread Starter
 
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I think I've checked it out. It's on the right side by the steering box or something similar.

Am I able to check the grounding of the switch trough the center box? I already stripped everything from there and measured the voltages from the switch and it showed +12V.
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post #9 of 10 (permalink) Old 07-20-2014, 12:44 PM
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I think I've checked it out. It's on the right side by the steering box or something similar.

Am I able to check the grounding of the switch trough the center box? I already stripped everything from there and measured the voltages from the switch and it showed +12V.

I don't know what you mean by "center box". The wiring diagram I looked at for the two models referenced above shows a brown wire going directly from the blower switch to chassis ground. I would switch everything off, disconnect the blower switch wiring connector and check for a brown wire on that connector. If it is solid brown with no other color it should go directly to chassis ground. Test for continuity to ground on that wire. If no continuity to ground, before I took the whole car apart I would cut the wire a couple of inches from the connector and splice in a new wire to the connector and connect that to chassis ground under the dash.


Disclaimer: I have never seen a roadster, only a wiring diagram. It may not be the correct diagram. At times the wiring diagram can be incorrect. I have never seen you, either. I have no idea of your abilities. My advice should be regarded as suspect until proven otherwise. Accordingly, proceed at your own risk.


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post #10 of 10 (permalink) Old 07-21-2014, 07:57 AM Thread Starter
 
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The problem was that the bridge which is connecting different fields was dirty. I sanded it a bit and it started working.

The blower itself is controlled by driving the ground from the switch to the resistor pack. The motor has+12 on all time when you're measuring it against battery.

Thanks for your help fellows
-Heikki
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