98 V70XC - A/C blowing hot air, P0116 code

[Ozark Lee]

Connect a wire from ground (something metal and not painted on the chassis) and then touch the pins on the middle socket of the relay, one at a time, with the other end of the wire.

...Lee

[mindshadow]

Ok, got it. So if that turns on, basically you're saying my ECU is hosed? Or could it be wiring further up that's the issue?

If they don't turn on, then what?

[mindshadow]

Alright, grounded out those middle wires and the fan turns on. Now what? And could that be related to the A/C not working (it won't turn the a/c compressor on because it thinks something is going on with the cooling)?

[mindshadow]

One more thing. Was reading around and, having seen a similar post, I unplugged the ECT sensor and started the car. Coolant fan kicked right on, so that seems fine. Of course the car was hard as piss to crank. It's been hard to crank since before I originally replaced the ECT sensor (of course then the temp gauge would fluctuate and wig out). When I originally did the replacement of the ECT, I ended up having to re-wire (minus solder, couldn't get around to soldering it) the harness the ECT plugs in to because the wires were corroded and crumbled. So I'm not sure if that's related, but I assume that if the connection was bad it would run just like the ECT was unplugged, right?

I also unplugged the a/c wire thingy (forgot the name, sorry) near the passenger's side firewall and jumped it to itself to see if the compressor would come on. Still no compressor.

So right now, here are the symptoms:

* Coolant light on, but car is not running hot, temp gauge is where it should be
* Hard to crank if the car has been sitting. I have to push the gas pedal down and it takes about 5-10 seconds for it to start.
* No A/C, which is what I care about more than anything right now because it's hot outside and the windows fog up when it rains.

[Ozark Lee]

You may very well be on the right track with the ECT sensor. It is one of the inhibiting inputs to the ECU that will defeat the compressor activation. This is specific to a 960 with a Motronic 4.4 but the theory is equally as applicable to your V70 with the Motronic 4.4.


Example 2
The example shows the circuit on a 1996 Volvo 960 with Motronic 4.4 and ECC.
The compressor is governed via a relay by the engine control module (ECM) depending on a number of input signals. With this connection the engine control module (ECM) can quickly (in advance) compensate for the changes in load that occur when the compressor is engaged and disengaged (= less jerkiness).


Function

The ECC control module calculates whether the compressor needs to be engaged to obtain the correct temperature in the passenger compartment. The calculations are based on the drivers requirements (= the settings of the control) and signals from a number of sensors.

If necessary, the control module transmits a signal (= requests engagement of the compressor).

The signal is sent to the engine control module (ECM) via the pressure switch (Pressostat).

The pressure switch (Pressostat) breaks the circuit if the pressure and therefore the temperature in the system (on the low pressure side) falls too low.

The engine control module (ECM) activates the A/C relay and the compressor is engaged.
(10 seconds after the start of the engine at the earliest - timer circuit in the control module).

The engine control module (ECM) disengages the compressor:

when the request to engage from the ECC control module/pressure switch (Pressostat) ceases.
at wide open throttle (WOT), for a maximum of 15 seconds (signal from the throttle position (TP) sensor).

at high engine coolant temperature (ECT), above approximately 125°C(257°F) signal from the temperature sensor).

at too high-pressure on the high pressure side, above approximately 30 bar (signal from pressure sensor).

The signals from the engine coolant temperature sensor and the pressure sensor are also used by the engine control module (ECM) to govern the engine cooling fan (FC).


...Lee

[mindshadow]

I think there is a bit of corrosion around the little.. connector.. thingies that go in the harness that connects to the ECT. I can see the green on the wires. Is there an easy way to clean that up, or will I need to find a replacement harness? Or would I be better to try soldering my connection first?

[mtd240]

I used these and bypassed the whole crumbled connector. 15k miles, 8 months, and it is holding up fine.

41WttNxCnmL._SY300_.jpg (11.42 KiB) Viewed 1605 times

[mindshadow]

What is that? Did you just crimp the wires together in there and bypass the harnesses all together?

[mtd240]

What is that? Did you just crimp the wires together in there and bypass the harnesses all together?

They are called "Scotchlok"s. You can buy them at Walmart.

Yep that's exactly what I did

[mindshadow]

Nice. So how much exposed wire do you need? Just enough to tie them together, then slide that thing over and put the crimp down? I left my long extension cord somewhere else, so soldering is a bit difficult for me right now.