Thread: TD5 Airconditioner efficiency.

Have you tested the Trinary pressure switch James?

Originally Posted by discorevy

Have you tested the Trinary pressure switch James?

Not yet Craig,

Busy busy, but yes that would be a logical thing to rule out early on.


I've ordered some new bd139 transistors and some other bits as well, I think the total was about $12.

I possibly won't have much to report here for a bit with work and life etc.. also whilst it might be my imagination, the weather seems a bit cooler than it was.

It's been a killer summer and autumn, hence my fascination with staying cool...

But I'll see how I go, I'm sure the standard defender AC is capable of more than most are getting out of it.

I dunno how big the condenser is on a defender. On my old Volvo wagon I cracked the condenser on a Kangaroo. When I replaced it I went to the local auto-fridgie and crawled through the catalogue to find the largest (in all 3 dimensions) parallel flow condenser I could fit. That made a massive difference. It could ice the evap on a 45 degree day and even after a prolonged spell at the lights it was "cold enough".

I had the condenser fan set up to run any time the compressor was kicked in and the car was doing less than 70.

Originally I had it set up with the compressor and condenser fan on the same relay, but it turns out the condenser fan was windmilling fast enough that if the car was over 60, the compressor clutch stayed engaged. Took me _ages_ to figure out why it kept icing up on country runs.

Anyway, my rambling point was, if you don't already have a parallel flow condenser, put in the biggest one you can make fit.

Originally Posted by prelude

Did you measure them removed from the pcb?

It does look extremely simple. I would not even call it a ECU since there is no microcontroller on it It looks more like a logic level converter into anything 12v that the higher power electrics in the car can work with. Should be easy to test signals/voltages over those chunky in/out pins.

But first, I'd look for dry solder joints before you hook it up and measure voltages across the pins (the lm324n datasheets are all over). The BD139 can not power the AC clutch on it's own, it is rated at 12watts max and 1 amp current so those transistors are only used to power relays. (these use typically around 200mA max) so that's why they run without heat sinks.

I reckon two of the more beefy diodes are there to protect the transistors from flyback of the relais coils. Easy to test those too.

Back to captain rightfoot The VC fan would likely not run fast enough at idle to cool the condenser when it's really hot. That's why the thermo should kick in eventually. Well, if you've done some testing we'll debug it further.

Cheers,
-P

My apologies all. What I meant was I've never seen the electric fan on the front run at idle. The AC shop claimed they saw it run but I'd like to see it myself. Clearly I'll need to get it all hot and get someone to rev it while I watch. Maybe it's Schrödinger's fan.

It's looking like I'm going to do another double desert run in October. I'd like this to be working to the best of it's ability.

Originally Posted by Captain_Rightfoot

My apologies all. What I meant was I've never seen the electric fan on the front run at idle. The AC shop claimed they saw it run but I'd like to see it myself. Clearly I'll need to get it all hot and get someone to rev it while I watch. Maybe it's Schrödinger's fan.

It's looking like I'm going to do another double desert run in October. I'd like this to be working to the best of it's ability.

If you pull the viscous fan off and leave the car idling (keep an eye on the engine temp with your diagnostic gear) with the AC on, pressure should rise enough to cycle the condenser fan. If you can get hold of a nano, I can turn the condenser fan on at much lower engine temp and that will definitely help at low speed travel across the Simpson.

Originally Posted by BradC

Anyway, my rambling point was, if you don't already have a parallel flow condenser, put in the biggest one you can make fit.

I believe the early TD5 condenser was a smaller serpentine unit with no electric fan.

Later ones had a parallel flow with electric fan, the same as the puma defenders.

They are INSANELY expensive for a new genuine unit.

We have an early TD5 defender with the old style condenser and no fan, we are currently rebuilding the whole vehicle, I'll have more idea on how well it works once that's going.

This is the early TD5 Defender setup.

Originally Posted by shack

This is the early TD5 Defender setup.

That looks like a conventional parallel flow. Oddly enough I can't see a defined subcooler there. Having said that, the inlet and outlet are on the same side, so there must be a division in the end tanks on the right hand side. That'll force the top of the condenser to work as a condenser as the gas flows right to left, then the liquid will fall to the bottom where it travels left to right to reach the outlet.

Anyway, if that's an early TD5 then it's not a serpentine. A serpentine is generally a single tube that snakes back and forward in a "zig zag" across the condenser. Worked perfectly well for R12, but r134a is so bad at rejecting heat they had to come up with something better.

In a car, anything you can do to reduce the condensation temperature is a bonus. Hiding it behind the intercooler is not going to help.