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  #141  
Old 07-15-2017, 12:17 PM
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I have been working on a 3.2 Cabriolet for quite some time now. My latest project has been the A/C system. I have converted it to 134a. The compressor works nicely and the pressure readings are good.
All the foam and panels around the condenser were missing and have now been replaced.
My problem is I can't seem to turn off the heat and/or close the heater control valve. The heater remains on under all conditions.
Can you advise me what steps are needed to remedy this condition? Could this be the relay you have just described?

Last edited by Bertocchi; 07-15-2017 at 12:22 PM.
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  #142  
Old 07-15-2017, 02:53 PM
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Quote:
Originally Posted by Bertocchi View Post
I have been working on a 3.2 Cabriolet for quite some time now. My latest project has been the A/C system. I have converted it to 134a. The compressor works nicely and the pressure readings are good.
All the foam and panels around the condenser were missing and have now been replaced.
My problem is I can't seem to turn off the heat and/or close the heater control valve. The heater remains on under all conditions.
Can you advise me what steps are needed to remedy this condition? Could this be the relay you have just described?
The heater control valve is open as the default, so maybe it's stuck that way. Or the cabin temp switch is disconnected or disabled.

For example, beginning with Post # 25 here:

How’s your Mondial's A/C working?

Last edited by Wade; 07-15-2017 at 02:59 PM.
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  #143  
Old 07-16-2017, 02:19 AM
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Quote:
Originally Posted by Bertocchi View Post
...
My problem is I can't seem to turn off the heat and/or close the heater control valve. The heater remains on under all conditions.
Can you advise me what steps are needed to remedy this condition? Could this be the relay you have just described?
Yes, IMO it's exactly the problem, I've had.

WRONG:
Turning the car/ignition/power OFF, the valve closes, turning the car/ignition/power ON, the valve opens. That was the problem at my car and it was caused by the wrong wiring (see post #135 and #138).

CORRECT it should be:
NO Power on the relay >> valve OPEN
Power on the relay >> valve CLOSED , the relay is (temporary) disconnecting the power to open (temporary) the valve. You will hear the "clicking" of the valve (open > closed > open > closed) with different frequency in addition of the temperature.

Just try the simple changing of the connector 87 and 87a , you can't kill anything.
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  #144  
Old 07-16-2017, 09:38 AM
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The temperature rheostat is connected. The relay does not appear to be on the relay panel...where do I find it?
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  #145  
Old 07-16-2017, 10:43 PM
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Quote:
Originally Posted by Bertocchi View Post
The temperature rheostat is connected. The relay does not appear to be on the relay panel...where do I find it?
See post #121 , second picture
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  #146  
Old 07-17-2017, 10:06 AM
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I found the relay and rewired the connector. I also replaced the relay with a Bosch 151.
When the engine is cold the A/C blows cold but as the engine warms the air from the duct increases in temperature.
I'm not hearing any "clicking" of the valve open and close? I'm also not able to late the temp sensor.
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  #147  
Old 07-17-2017, 11:03 AM
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Quote:
Originally Posted by Wade View Post
The heater control valve is open as the default, so maybe it's stuck that way. Or the cabin temp switch is disconnected or disabled.

For example, beginning with Post # 25 here:

How’s your Mondial's A/C working?
The temperature sensor resistance is 9.3K ohms at 75 degrees F.
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  #148  
Old 07-17-2017, 12:32 PM
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I am guessing this is the evaporator temperature or heater temperature sensor. It too is reading over 9K ohms and was tucked up under the dash.
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  #149  
Old 07-17-2017, 03:11 PM
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Originally Posted by Bertocchi View Post
The temperature rheostat is connected. The relay does not appear to be on the relay panel...where do I find it?
Here is a pic with the relays indicated.

Some folks have found the relays in the incorrect positions and someone found the wiring TO one relay was incorrect. Italians! Wadda ya gonna do?
Alden
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  #150  
Old 07-17-2017, 03:17 PM
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Thanks, I found those and sorted them out. I'm now under the passenger's foot well looking at the control units.
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  #151  
Old 07-17-2017, 03:47 PM
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Quote:
Originally Posted by Bertocchi View Post
The temperature sensor resistance is 9.3K ohms at 75 degrees F.
See the attached.

BTW, do you have the Mondial 8 / QV workshop manual? Section H has a lot of details.
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  #152  
Old 07-17-2017, 03:50 PM
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I am working with an earlier wiring diagram and it is looking like some of the wire coors are different but according to what I see the heater control valve gets its signal from the Bosch control unit pictured here.
The valve itself appears to be inside the blower assembly (of course).
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  #153  
Old 07-17-2017, 04:10 PM
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Quote:
Originally Posted by Bertocchi View Post
I am working with an earlier wiring diagram and it is looking like some of the wire coors are different but according to what I see the heater control valve gets its signal from the Bosch control unit pictured here.
The valve itself appears to be inside the blower assembly (of course).
No, the valve is outside of the box. See item #4.

1987 Mondial Heater Water Pump Switch Question
.
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  #154  
Old 07-17-2017, 04:12 PM
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@Wade...I have a wiring diagram and parts manual for an 84. No repair manual. The resistance chart was posted in the thread you mentioned. I measured the sensors removed from the system.
The car lives in Florida and wouldn't be terrible if the heat valve was closed permanently. This is costing a lot to repair.
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  #155  
Old 07-17-2017, 04:42 PM
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Permanently closed can end up causing internal corrosion with the heater core (no coolant flow), and then leakage.

But yeah, not a high priority.
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  #156  
Old 07-17-2017, 05:04 PM
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Quote:
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Permanently closed can end up causing internal corrosion with the heater core (no coolant flow), and then leakage.

But yeah, not a high priority.
Last resort. It took some doing but I located and removed the heater control valve. During a bench test it did not close completely.
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  #157  
Old 07-18-2017, 12:55 AM
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Quote:
Originally Posted by Bertocchi View Post
... During a bench test it did not close completely.
because of not having closed completely (or even correctly) for many years... corrosion ?

David, do you need the correct wiring diagramm for a 3.2 , it's much different from the 84 (QV) diagramm ?
If so, please PM me with your personal EMail address, that I can send you a pdf file.

Last edited by 2281GT; 07-18-2017 at 01:01 AM.
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  #158  
Old Yesterday, 04:40 PM
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Thank you Markus and Wade for all the useful info. It is now working very nicely.
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  #159  
Old Yesterday, 07:54 PM
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Awesome, and glad I could help.
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