Air conditioning clutch not engaging

[Ben123]

Hi All,
This is my first time post seeking some advice on my Toyota LX470 2004 Landcruiser- location Australia.


I have purchased after it had an engine and transmission conversion.
The engine is a GM 6.5 TD with mechanical controlled fuel pump, and the transmission is a GM 4L80e with 6 speed conversion and Compushift II controller.
Since purchasing it has tested my knowledge, I still seem to have more questions than answers.
The main issue that I have not been able to resolve since purchasing- I found the air conditioning compressor was hard wired to operate the A/C.
I am not happy with this as the compressor never turns off, I want it to be controlled by the climate control system.
I have returned the compressor wiring to oem. Now when I earth the compressor wire at the ECU the compressor engages.
Problem is the ECU won't switch the earth signal??
A lot of ECU wires are cut and not used due to the conversion, problem is I don't understand the Lexus system enough to know the list of ECU inputs that is required before the engine ECU is allowed to activate the compressor.
Items that have been checked;
Pressure switch circuit checked- all good
A/C on/off switch input signal all good
Thermister sensor checked- all good
Replaced engine ECU- no change
Replaced A/C amplifier ECU- no change
The Stanadyne compressor does not have a lock sensor- 1000K ohm resistor connected to the lock sensor return signal wire (when no lock sensor signal is received the A/C clutch should engage for 5 seconds then switch off. The A/C clutch does not engage at all, at any-time)
The cluster gage tacho has never worked- I have ordered an SGI-100BT signal converter. (I am hoping the engine rpm signal will be the missing ECU input required to activate the A/C)

I hope some-one knows and is able to share all ECU inputs and circuit bypasses required to turn on the compressor.
Some-one may also know how to connect the GM front crankshaft speed sensor to the SGI-100BT.

Thanks in advance,
Ben.

 

[MrMarty51]

Welcome to the forum 123.
I do not understand one thing about such a conversion as this.
Seems with a wiring diagram, a set of gauges hooked to the AC system that it should not be that difficult to get wired up.
Probably follow how the original AC system was wired to the original AC units.

 

[Ben123]

Thanks MrMarty51, I thought the same, I do have the wiring diagrams and the system circuit diagnostic information and gages. I have a fair bit of auto A/C knowledge, but this has me stumped.
To me I think the problem is an ECU mapping issue that has been introduced when the engine was changed from petrol to diesel. I have reset the compressor wiring system back to factory. The factory system uses the ecu to cycle the compressor. Before the ecu does this, a set of ecu input parameters need to be met. I am currently waiting on a signal converter to arrive so I can get the engine tach working, I need this because the engine is not factory. I have been told some ecu systems require engine speed before the ecu will engage the compressor. This seems plausible to me as you would want the compressor clutch to engage after the engine has started.

 

[Ben123]

So, bit of an update. The signal interface has arrived and is now installed and supplying an input signal to the engine ecu. As a result the tacho in the cluster gauges now works and as a bonus, because the ecu sees the engine rpm signal, the ecu is turning on the aircon compressor. Yes after 12mths trying to “fix” the a/c system, it was the lack of engine rpm signal causing problem the whole time.

 

[ak diesel driver]

Thanks for coming back to update

 

[Will L.]

Wow… that is one ai would never figure out. Glad you have it now.
If you ever get the chance to post pics of the install or links to YouTube videos of it - we’d love to see them.

 

[monkeywrench0786]

As soon as you said tach signal missing I said the same thing, ecu reads the tach signal to lock compressor to step up engine speed so compressor turns fast enough to keep refrigerant moving for pressure maintaining. Glad you got it solved, ran into this on wife's 00 Toyota solara which is based in the Lexus,es300,Camry,solara genre

 

[Ben123]

As soon as you said tach signal missing I said the same thing, ecu reads the tach signal to lock compressor to step up engine speed so compressor turns fast enough to keep refrigerant moving for pressure maintaining. Glad you got it solved, ran into this on wife's 00 Toyota solara which is based in the Lexus,es300,Camry,solara genre

Haha, I have been chasing this issue for so long, thinking it was an issue with the A/C system. Luckily, I was speaking with an auto sparky about all the work I had done with no success. As soon as I told him the engine was custom and most of the engine ecu wires were disconnected, that's when he realised the issue- ecu needs to see engine rpm before allowing the A/C clutch to engage- I owe him a carton of beer!
I had trawled the internet and could not find this snippet of info recorded anywhere!!
My 6.5 engine does not have a step up engine speed solenoid on the DB2 injector pump, so the engine revs don't increase when the compressor is turned on. The engine idles at 600Rpm, the additional load from the compressor is barely noticed on the tach needle, so no need for me to change this.
What I still need to do is get the A/C condenser thermo fan setup to cycle with the compressor, as currently it is doing nothing.
Some other issues that has now been resolved as a result of the tach operating;
- Oil pressure gage now works.
- Red A/T OIL TEMP warning light is no longer lit up after starting.

 

[Ben123]

Wow… that is one ai would never figure out. Glad you have it now.
If you ever get the chance to post pics of the install or links to YouTube videos of it - we’d love to see them.

This is the info I have recorded for my future reference;

Aircon fixed by getting OEM engine tach to operate on dash
Engine ecu E9-24, 25 wires were piggy backed with 100 series petrol V8- the tach started to work and the aircon clutch engaged.
Dakota Digital SGI-100BT Universal Signal Interface Unit connected to operate engine tach. The Diesel and Tach input options did not register any input signal by the 2 wire induction crank speed sensor. The Speed input section recognised the signal.
Location- behind glovebox compartment, near engine ecu.
Engine speed sensor located near front LHS pulley, has a black and white wire.

LX470 SGI-100BT
E11-9 12V Black, red stripe, Ignition pwr IGNITION + (made harness red wire)
E11-15 White black stripe, Earth GROUND – (Made harness white/black stripe wire)

Chev 6.5Lt diesel induction Black wire SPEED INPUT (made harness blue wire)
2 wire engine speed sensor White wire SPD- input (made harness green wire)

Engine ECU E9-25 L, crank sensor OUT 3 (made harness orange wire)
Engine ECU E9-24 G, crank sensor GROUND- (made harness White/black stripe wire)

1K ohm sensor connected between OUT 3 & Ground –
to apply additional load on output signal- so the engine
ecu identifies the SGI-100BT output signal. (Without this resistor the tach does not work)

The interface setup was set using the Dakota Digital App via blue tooth.
The Input Type must be set to low.
The Pullup option does not make any difference.
The Input/Output must be set to Low/Low
2.3 is the ratio change required to produce accurate tach reading


Final install located next to the engine ECU, behind the glovebox.


Original Toyota 2UZ-FE V8 Petrol engine crankshaft sensor generates 1.9ACV 440Hz at idle and runs off a 32 tooth gear.

 

[Ben123]

This is the info I have recorded for my future reference;

Aircon fixed by getting OEM engine tach to operate on dash
Engine ecu E9-24, 25 wires were piggy backed with 100 series petrol V8- the tach started to work and the aircon clutch engaged.
Dakota Digital SGI-100BT Universal Signal Interface Unit connected to operate engine tach. The Diesel and Tach input options did not register any input signal by the 2 wire induction crank speed sensor. The Speed input section recognised the signal.
Location- behind glovebox compartment, near engine ecu.
Engine speed sensor located near front LHS pulley, has a black and white wire.

The interface setup was set using the Dakota Digital App via blue tooth.
The Input Type must be set to low.
The Pullup option does not make any difference.
The Input/Output must be set to Low/Low
2.3 is the ratio change required to produce accurate tach reading
View attachment 98103

Final install located next to the engine ECU, behind the glovebox.
View attachment 98101

Original Toyota 2UZ-FE V8 Petrol engine crankshaft sensor generates 1.9ACV 440Hz at idle and runs off a 32 tooth gear.
View attachment 98102