XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

1996 XJS RH Blower Fan will not stop

 
  #1  
Old 05-27-2019, 05:53 AM
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Default 1996 XJS RH Blower Fan will not stop

I have an interesting problem. Right side blower fan will not stop running even when the car is shut off. I have to go and take the fuse out the fuse box to stop the fan otherwise battery will be drained. I have seen similar posts about a relay getting stuck in an open position thus it keeps running since the fuse feeds power to it.
However I can't locate the relay that controls the right blower motor fan. to add to the frustration it keeps bringing hot engine air. With summer heat it's becoming difficult.
Not sure if the same relay would effect the A/C control panel. The temperature and fan speed knobs don't respond as well.
Thank you
 
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Old 05-27-2019, 07:09 AM
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Originally Posted by Sonny_D View Post
I have an interesting problem. Right side blower fan will not stop running even when the car is shut off. I have to go and take the fuse out the fuse box to stop the fan otherwise battery will be drained. I have seen similar posts about a relay getting stuck in an open position thus it keeps running since the fuse feeds power to it.
However I can't locate the relay that controls the right blower motor fan. to add to the frustration it keeps bringing hot engine air. With summer heat it's becoming difficult.
Not sure if the same relay would effect the A/C control panel. The temperature and fan speed knobs don't respond as well.
Thank you
Relays are located in or near the fan housing. Yes, it could be the relay stuck on the bad side, or the opposite side is powering it due that one being failed or shorted, and shorting continuous power to the other side.
See wiring diagram.
 
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Old 05-27-2019, 08:34 AM
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Thank you for the information. How difficult is to access the fan housing? For a normal non-mechanic handy man?
 
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Old 05-27-2019, 10:29 AM
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It's probably more likely the Darlington transistor on the fan housing, this is what makes it variable speed. It's possible to be the high speed relay, but it is only activated when full speed of the blower is called for.

I've only removed the drivers side to rebuild the board, with the passengers side you'll have to remove the airbag to access the bolts. That's not too difficult to do, just follow the manual and it's not too bad. Here is the procedure from a 1978 car, which is basically the same the only difference is you'll have no glovebox to assess the blower. Replacing The HVAC Blower Modules.
 
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Old 05-27-2019, 12:07 PM
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Thank you for the info. If I plug the fuse back while the car is off with the keys out of ignition the blower unit stays on but all A/C controls at not working. You think its the fan module?
 
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Old 05-27-2019, 06:32 PM
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Originally Posted by Sonny_D View Post
Thank you for the info. If I plug the fuse back while the car is off with the keys out of ignition the blower unit stays on but all A/C controls at not working. You think its the fan module?
It was for mine! The control module for the fans gets power all the time, the transistor shuts it off. If the transistor goes bad, then power flows all the time, as it's not supplied with switched power, rather it gets constant power.

Here is a description of the rebuild process: Air conditioning blower control
 
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Old 05-27-2019, 09:42 PM
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Originally Posted by Sonny_D View Post
Thank you for the information. How difficult is to access the fan housing? For a normal non-mechanic handy man?
Sorry for not answering right away and till now.
In fact I have not had the pleasure/displeasure of gaining access to the blower, darlington transistor or relay for each blower motor so not familiar with its access. I was helping a chap on Facebook where his was also running on high speed with ignition off. For that one, the opposite side relay was found rusted and possibly causing a short to turn the opposite side on all the time.
Yes, possibly the darlington transistor, but would not think it would fail to the on position, but more to the open position not passing any voltage to the blower.. I would start with changing or swapping relays if you know how to access.
Perhaps the chap is on this forum as well and can provide some access to the relay assistance.
 
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Old 05-29-2019, 04:31 AM
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You will have to remove the blower as the relay and Darlington are inside the blower assembly.

Check the relay first as it is easy but my guess is the Darlinton has failed short circuit which will turn the blower on all the time even with the ignition off. If it is the Darlinton you can substitute a MJ11016 available from RS Components.

This is a circuit diagram I made from my blower when I had it out for repair.

 

Last edited by warrjon; 05-29-2019 at 06:33 AM.
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Old 05-29-2019, 05:29 AM
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Originally Posted by warrjon View Post
You will have to remove the blower as the relay and Darlington are inside the blower assembly.

Check the relay first as it is easy but my guess is the Darlinton has failed short circuit which will turn the blower on all the time even with the ignition off. If it is the Darlinton you can substitute a MJ11016 available from RS Components.

This is a circuit diagram I made from my blower when I had it out for repair.

Warrjon, perhaps different years yielded different blower circuits. In my 95 elect diagram, the blower circuit seems different from your depiction. His '96 would be closer to the 95 diagram in that the motor ground leg is controlled by the high speed relay OR the darlington when high speed relay is open-not energized. When relay is not on, contacts open, then the darlington takes over in a variable mode. In your depiction, your motor ground leg shows only controlled by the dalington to ground. I don't see any tie of the motor ground leg to the relay open /close contacts from your drawing. Again, your car year and circuit may be different. I have attached a 95 circuit and notes.

 
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Old 05-29-2019, 06:28 AM
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That is the same circuit just laid out differently I missed the dot on my circuit. I only drew this for my reference when I repaired my blower

The relay would not turn the blower on if it wasn't connected between the DT and motor.

I have just updated my cct
 

Last edited by warrjon; 05-29-2019 at 06:34 AM.
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Old 05-29-2019, 08:40 AM
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Thank you to all that took time to respond. I will start working on it following this helpful leads and will post results once finished!
Thanks again
 
 
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