yeah, 1991+ 740's were really 940s in many ways, although they still had hte older style trunk on the sedans, and the 740 style seats

in particular, 1991+ got an entirely different HVAC control with rotary ***** for fan, temp, and vent selection.

 

Yes, this unit looks more like the one in my 960. It has a circuit board, whereas, the '90 is really an old-fashioned mechanical affair.

 

well, the 960 has full electronic climate control, with a **** calibrated in degrees and automatic fan speed and vents. ECC *was* an option on more loaded 940's. the panels do look similar but the function is quite a bit different.

 

...and expensive and/or difficult to repair, as well.

 

other than the control panel, the main difference with ECC is that the fan motor has a transistor power amplifier speed controller in place of the resistor bank that the MCC uses, either of htese stock on the side of the fan housing.

 

Only the 1991 940SE, which is really a turboed 960, had the ECC--mercifully no other 940 did. Small differences or not, that 760/960 ECC never seems to work right or be able to be repaired successfully... I had several 1991 SEs, and 760s and all the "luxury" ideas Volvo put in these cars were a major PIA!

 

I kept tracing the voltage back until I found the problem. And since this is a thread about the 1992 760 and mine is a 1990, I'm going to post my results with pics for anyone else who might run into the same problem. Turns out there is a relay behind the glove box, and although I didn't see any problems with the circuit board, the contacts were oxidized. Once cleaned up, the AC kicked on and works fine. I also took the time and lubed my blower motor (again). That squeal is ungodly! Anyway, thanks for the hints!

 

huh, we had a 960, a S90, and a 940SE (not at the same time), and the hvac worked fine on those three the whole time we owned them.

 

Thanks for the professional tips. My 92 940 AC just blows hot air. I connect (+) battery power to compressor clutch black wire and it clicked which means the compressor is good. Next..
1. I will check if there is power to the socket of pressure sensor mounted on the drier.
2. If it has no power I will reflow solder to AC control unit.
3. If it has power, I will jump the connection to see if compressor engaged. If compressor engaged then I will change the pressure sensor on the drier

Does these make sense to you? Thank you

 

Makes sense to me, yes.

 

Hi I thought I'd ask on this thread before making a new one, same exact car. I unplugged the low pressure sensor and tested at the plug. I have power to one lead of the plug at the low pressure sensor when the climate control is engaged. I jumped the other lead to the positive end of the battery and the ac clutch engages and blows cold air.
So I know I have power at the plug, and I know the compressor works, and I know there is continuity from the plug to the compressor, so I thought the sensor must be the issue.
The problem is that I tried jumping one lead of the plug to the other, and it doesn't work, so maybe the sensor is fine? I am totally confused how one end is getting power, and the compressor works fine when I power the other end, but it doesn't work when jumping it. The only thing I can think of is that the battery has 13 volts and the plug has 11 volts, but is that a big enough drop where the compressor clutch won't engage?
Maybe there is something obvious I am missing in my test?
Thanks. If no replies I'll just post a new thread.