Defender 300tdi - Aircon electrical - Thermo Amp

[MrNeil]

My 1998 Defender 300tdi just recently developed intermittent aircon issues. Clutch not engaging.

On inspection the wiring to the Thermo Amp is running hot and the pin/connector is blackened/melted.

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(Located in battery compartment, aircon electrics / Thermo Amp talked about extensively in this thread from 2010/11 - Air con wiring advice needed? (https://www.aulro.com/afvb/90-110-130-defender-county/119231-air-con-wiring-advice-needed.html))


The charring seems to be on the connector for the red wire. Which, referring to this diagram,

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looks to be coming from the blower switch on the dashboard. The thermo switch is always dialed all the way clockwise as I currently live in Darwin...


Relay wasn't switching / clutch wasn't engaging. I've doused the connector in WD40 which has got it working again but still hot connection.


Have removed the Thermo Amp, taken the circuit board out. See attached pics.

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The part hasn't been available for years so the only options as I see it are fixing the board or bypassing. Which as I understand it would lead to the condenser icing up under use.


Could an electrician / someone in the know advise whether it might be fixable / connection(s) could be resoldered / cleaned up or is the board stuffed?

EDIT :- I'm taking it into a local phone repair shop tomorrow who will resolder. I'll update here after...

[shack]

The actual unit doesn't look damaged, I'd be trying to save it.

On the heat side of things, usually only 2 things cause excessive heat.

1. Too much current draw - IE something downstream is dying.

2. A poor connection.

If you find where the most heat is for point 2, it's most likely right at the connector.

Once they have got hot, they can't be saved.

The protective coating comes off and they rust, and the tension guess out of the metal and they become loose, which becomes a self perpetuating problem.

I'd start by trying to fix number 2, as you have to do that anyway, you'll be able to see then if the Problem continues and you need to look elsewhere.

[MrNeil]

So I got the pins resoldered at the phone repair shop. For a very reasonable $30. They did all the pins, not just the 2 worst ones.

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Aircon is running consistently now. Even feels a bit colder. Psychosomatic or maybe better current flow all round.

The connector still running warm but not hot like previous. Normal?

I'm trying to change the connector now. Not having any luck locally so far. Jaycar, Supercheap, the usual suspects. Searching online too but not seeing anything similar.

Any suggestions? I'll swing by a couple of local autoelec places also.

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[shack]

A kf2510-8 may be close, but possibly not correct.

Other owners have simply soldered the wires directly on, this would definitely work.

It's also suggested to maybe use the Thermo amp to just fire a relay that takes the load instead, that would be best.

[jboot51]

I removed the connector and pins, soldered the wires directly onto the board.
No issues for 10 years.

[philandmickey]

Hi

I replaced my Thermo amp with a 12 volt temperature controller, from ebay it was a long time ago but like this -

Digital Temperature Thermostat STC-1000 Controller Heating Cooling LCD 12V-220V | eBay (https://www.ebay.com.au/itm/134595575519'mkcid=16&mkevt=1&mkrid=705-154756-20017-0&ssspo=19tngpwftdq&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY)

It took a bit of thinking regarding the wiring, I used the same diagram you have, and the instructions were a little unhelpful but got there in the end its been perfect ever since.
That was probably 6 or 7 years ago.

[MrNeil]

I removed the connector and pins, soldered the wires directly onto the board.
No issues for 10 years.

The local Land Rover guy mentioned similar. Wires soldered directly, as you say, with a Deutsch type connector.

Daytona DCON8P Deutsch Weatherproof 8 Pin DT Connector Kit (https://sydneytools.com.au/product/daytona-dcon8p-deutsch-weatherproof-8-pin-dt-connector-kit).

My soldering skills aren't up to it right now so I'll have to seek out someone to do it. Might go back to the phone repairs guy.

[MrNeil]

Hi

I replaced my Thermo amp with a 12 volt temperature controller, from ebay it was a long time ago but like this -

Digital Temperature Thermostat STC-1000 Controller Heating Cooling LCD 12V-220V | eBay (https://www.ebay.com.au/itm/134595575519'mkcid=16&mkevt=1&mkrid=705-154756-20017-0&ssspo=19tngpwftdq&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY)

It took a bit of thinking regarding the wiring, I used the same diagram you have, and the instructions were a little unhelpful but got there in the end its been perfect ever since.
That was probably 6 or 7 years ago.

Interesting. Possible you could take a pic of your setup and upload?