75ZT Community

Hi All,

I set about fitting a FBH (Fuel burning heater.) remote module from ThinkTankElectronics. I got everything wired-up, but when starting the ignition my ATC (Automatic Temperature Control) panel is dead (no lights at all). I double/triple/quadruple checked all connections and used a multimeter from the ATC panel plug back to the module to confirm there was continuity. I have checked all fuses associated with the ATC, nothing was blown.

I then took the 4 wires at the module end and joined the 2 matching pairs, thereby taking the module out of the equation. Still, the ATC panel was dead. I concluded that I must have a bad solder joint on the loom side of the ATC, so I removed the heatshink to check - the connections were good.

I'm at the point where it looks like a dead ATC panel to me. I can only guess that it is just co-incidence that the panel decided to die at this time, or that my wiring in the module has somehow killed the ATC panel. I have checked the wiring against the wiring diagram provided with the module about 10 times now, and I am certain I had it wired correctly.

I am able to remotely start the FBH using my remote, everything works really well....except the ATC panel. I left it running for the 5 minutes to see if the ATC panel would light, unfortunately it did not.

Does anyone have the pinouts or wiring diagram for the ATC plugs? Is it possible that by wiring incorrectly at the module end I have killed the ATC panel? Are dead ATC panels very common? Does anyone have any other suggestions before I buy a new ATC panel?

Hoping that Raistlin can help out



Thanks,

Dan

You did switch it on didn't you ?

Yep, I did try switching on/pressing the buttons but nothing

Hi Dan, assuming you've cut the right wires, and I'd say you have if you've checked them that many times, then it is possible that you've connected the plug ends to the module terminals that should be connected to the loom ends and vice versa. In which case, there would be no function of the ATC ecu as you describe. However, mis-connecting in that fashion wouldn't damage your ATC ecu, as all you would have done is open circuited the power supply, which would be the same as fuses 11 and 33 being ruptured in the passenger foot-well fuse box. IE, when you re-connected the wiring as per original, the ATC ecu would continue to work as previously.

All the ATC part of the mod does is to provide a pair of 12 volt power supplies when the ignition is off, as the fuse controlled supplies are switched by the ignition, hence you can't switch the panel on under normal circumstances, without the ignition being on. Other than that, the module provides a pass-through path so that when not being used, the ATC ecu works as per OEM.

So, again assuming that you've cut the correct wires, I can only surmise that the ATC ecu perversely decided to fail at a wholly unpropitious moment.

Just to recap, the wires you should have cut are White\Orange to ATC ecu C0792-2 and Light Green/White to ATC ecu C0792-3.

I've never heard of an ATC failing, it's always turned out to be a fuse on those where I've heard of problems.

Just in case it helps, fuses 33 and 11 on older cars (grey fusebox), but fuse 4 should be checked too as it also supplies the ATC with permanent power. On newer cars (red fusebox) the fuse numbers are 34 11 and 27.

In all cases, double check you have power on the purple green (pin 1) white orange (pin 2) and light green white (pin 3). when the ignition is on. Pins 4 and 8 should be ground.

Thanks for the help Paul.

Just to confirm are the 2 wires are on the same white plug?

If I use a multi meter on the wires should I be seeing 12v? I havent tried yet, but guess if I can prove the voltage is getting there it confirms the fuses are good and points back to the ATC panel.

Yes, both wires are on the same plug, as is the third that I mentioned. And yes, with ignition switched on you should see 12v on all three wires. But don't forget that third wire as without it the panel doesn't work (though it may not be dead like yours). My suspicion from the symptom is the white orange wire is not getting 12v.

Thanks Duncan. I've just tested and I am not getting 12v on pin3 when the ignition is on. I suspected my soldering so I tested from before the solder and still did not get 12v. I checked fuses 34, 11 and 27 again. I tested them using the multi meter just to be sure, they are all good.

As you say, it looks like it may not be the ATC unit, but I'm a bit stumped as to what to try next....

Pin 3? You mean light green / white at the ATC ecu Dan?

Yes, light green/white.

Have you still got the wires twisted together or are they connected to the module?

They are currently twisted together and bypassing the module. As mentioned, I tested from the loom side where I cut to bypass my soldering and the wiring added and still no 12v. Should there definitely be 12v on light green/white? I tested it with the ignition on but the engine not running.

Yes there should be 12v on that with ignition on. How have you checked the fuses?

I set the multimeter to resistance mode and put the fuses across it to check the resistance dropped to 0 or 0.1

Appreciate the help, just hope we can get to the bottom of it!

OK, no problem. Just I've seen a few that have been pronounced as OK, by visual inspection, but weren't.

It has to be a cable break then, I think.

I did inspect the wire as are much as possible and it looked good. Does anyone know the path it takes behind the dash or know the exact fuse number that feeds the light green/white wire?

It's getting frustrating not having a working unit, the car was badly steamed up today and I couldn't do anything but wipe the windows with a cloth

I probably won't get a chance to look Ito it further until Friday or the weekend. I'll report back, hopefully with good news

It's one of the three I mentioned in my reply above. I'll have a look and check which one. Which fuesbox do you have, red or grey?

Thanks very much. It is the later red fuse box.

dan_storm wrote:Thanks very much. It is the later red fuse box.

That'll be fuse 11 then