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Old 11-27-2018, 05:19 PM   #1
missthe1122
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Default Need advice on 1990 760 Turbo ECC climate control

My second venture into 700 turbo wagons is a 1990 760 turbo I picked up for $1000. I rebuilt the suspension with new steering rack, ball joints, tie-rod ends, shocks. I converted the rear from nivomat with the IPD conversion kit (it was on sale). It runs beautifully, however the blower control does not function and the AC button flashes continuously. I read that this is an error signal and the blower might be disabled by the system. I tried to follow these instructions to invoke diagnostics mode:
1. shine bright light on solar sensor
2. set blower control to [AUTO]
3. set function control to [vent]
4. depress recirculation switch
5. press and release AC button.
Unfortunately I could not complete this successfully over several tries so I could not get a hint as to exactly what is wrong. All I need right now is the blower so I can get some heat and defrost going. Is there a way to bypass the ECC and operate the heater fan manually? Or, is it simply that the fan doesn't work? All the fuses are intact. I'm hoping for an easy troubleshoot and fix. It's cold outside!
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Old 11-27-2018, 05:44 PM   #2
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I ended up wiring the blower motor though A Bosch ballast resister and a power switch on my 88 765. This way the EEC is not controlling the blower. A radiator fan motor ballast resistor controls the voltage to the blower motor. I have tried .4 ohm which runs at high speed. .6 ohm which runs slightly slower than high speed. Somewhere around 1 ohm should result in medium speed. Maybe run different spec ballast resistors for more blower speeds.

There are 12 volt switched, and 12 volt constant terminals on the back of the relay panel to make wiring connections. Connecting a ground behind the radio console to the blower motor. Running a wire from 12 volt switched through a heavy duty switch through a ballast resistor to the other blower motor will make the blower run. Just use a wiring pigtail from a GM car that has the blower motor under the passenger side dash to make the connection. This blower motor used on the 88-90 760/ 92-94 960 is a GM Delco part that fits GM cars. Never try to fit an aftermarket blower motor made to fit a GM car. it needs to be an OE GM part to fit. Cars that use this type blower motor are Cavalier, Sunfire, Camaro, and Firebird, plus a few other GM models.

Connecting the blower motor in this fashion has not had any effect on the rest of the EEC controls.

The EEC issue is that the blower motor reports back to the control unit that it didn't start properly.
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Old 11-27-2018, 06:13 PM   #3
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Thanks lummert. I was thinking about direct wiring the blower motor, but the addition of a ballast resistor is prudent advice that I didn't think of. Just curious. Is the diagnostic mode procedure correct? This seems like a convoluted way to trigger diagnostics. Shine a bright light at the solar sensor? Why is that necessary?
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Old 11-28-2018, 12:50 PM   #4
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Maybe this is what we both need to read...

https://www.matthewsvolvosite.com/fo...ic.php?t=54553

More...

http://home.eol.ca/~clubshub/760start.htm

Last edited by lummert; 11-28-2018 at 01:13 PM..
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Old 11-28-2018, 10:57 PM   #5
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A/C needs to be off then you press the a/c button twice to enter diag mode. You have to shine a light otherwise the unit will flash a code for no signal from the light sensor.

If you can't get it into diag mode the climate unit is probably kaput. Pretty common for them to die
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Old 11-30-2018, 01:46 PM   #6
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Quote:
Originally Posted by miguel.760ti View Post
A/C needs to be off then you press the a/c button twice to enter diag mode. You have to shine a light otherwise the unit will flash a code for no signal from the light sensor.

If you can't get it into diag mode the climate unit is probably kaput. Pretty common for them to die
Thanks for the reply Miguel. As soon as I start the car with both switches set to AUTO, the AC button begins to flash, but the compressor isn't engaged and I doubt it even works. I do have a '93 960 parts car that appears to have the same ECC system. Is it a self-contained unit, or is the controller located remotely?
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Old 11-30-2018, 01:49 PM   #7
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Quote:
Originally Posted by lummert View Post
Thanks again, lummert for good information. This seems like something I will explore. I do have a parts car with the same system, so that's an option. It seemed to work while the car was running.
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Old 11-30-2018, 03:30 PM   #8
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I removed the controls from my 960. Will install it and see what happens. I remember having to press the AC button to turn the fan off. I'm hoping lummert's link will help me to fix the unit. Fingers crossed.
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Old 11-30-2018, 09:40 PM   #9
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I have installed a .4 ohm and a .6 ohm Bosch ballast resistors wired in series to the blower motor. The voltage to the blower motor with the engine running is 8 volts. So that is a 6 volt drop. These Bosch ballast resistors are made for reducing the voltage to radiator fan motors, possibly on a Ford truck.

This type...

https://www.newegg.com/Product/Produ...0PG-00B5-00071

Last edited by lummert; 11-30-2018 at 10:04 PM..
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Old 12-02-2018, 08:52 PM   #10
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From what I have seen the control pannel dies. Manly the a/c switch quits which can be repaired by adding a switch. I like a nice blue rocker switch that lights up when engaged. As for fan speed I thine ther is a resistor pack in the air box.
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Old 12-02-2018, 08:59 PM   #11
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OP, if all else fails find the Volvo UK Club and their 700/900 pages. Your ECC information and repairs to same should be found therein.
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Old 12-04-2018, 04:08 PM   #12
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Quote:
Originally Posted by DET17 View Post
OP, if all else fails find the Volvo UK Club and their 700/900 pages. Your ECC information and repairs to same should be found therein.
Thanks for the reply, DET17. I did look at the ECC repair pages you cited. I had an extra ECC control unit I extracted from my 960 parts car, installed it and it did the same thing (flashing AC button + no fan). It did work in the 960, so I am assuming that the problem is not in the control unit. It was so easy to remove the blower fan (having been through the 240 nightmare already). I had it out in 5 minutes! I ran the motor directly from the battery and it spins perfectly. I backtraced the wiring to what the wiring diagram calls the ECC/power unit. Apparently this varies the fan speed instead of static resistor packs? I'm not prepared to mess with it since it looks like a pain to get out and I don't really understand its function. I saw a cheap GM resistor pack on eBay with the same blower fan connector, so I'm going to try this with a 4-position switch so I can get through the winter and revisit this problem in the spring. I hope I can rig something up successfully. I'll try it on the bench first. I definitely want to drive this car - but not without heat or defrost.
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