RRC heater speed control resistors now measured.

With a nod to Mr H Robinson I jury rigged my heater assembly to a battery and measured I through and V across the heater resistors.

Results are: R1 = 3V4 and 8A2 giving a value of 0R4, R2 = 6V4 and 4A8 giving a value of 1R3. As a check R1 + R2 = 7V1 and 3A9 giving a value of 1R8

Power is between 26 and 30W depending on which resistor is connected.

So I reckon that one each of these from RS:

615-0476
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and 160-900
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or 107-4080
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would do.

I wasn't intending to add any extra heatsinking above what is already in the heater case - which ain't much.

Any thoughts?

TIA

Richard

Reply to
Richard Savage
Loading thread data ...

So, with a measured 12V supply and R1 in series with the fan, R1 drops

3.4V and 8.2Amps flows ?

Steve

Reply to
Steve Taylor

Hello Steve

Not quite 12V; my bench supply only manages 5A. I used the RR battery. With no resistors in series with the fan and the battery measured at 11.7V, the fan was drawing 13.2A!

But apart from that yes, the voltages are as measured across R1 and R2 respectively. Surprising figures?

Cheers

Richard

Reply to
Richard Savage

Sounds plausible, about 70W in the fan.

Steve

Reply to
Steve Taylor

You're still going to mount them at the original position... ie. in the airflow path? They'll handle it with cooling assistance. I've scared a few customers with the amperage figures after they've complained about burnt out switches and wiring in pre-MA Discos.

While you've got the system apart - I'd get some good quality grease and service the bushes in the fan motor. As they dry out and the motor gets harder to turn - imagine the extra current required.

--Craig.

Reply to
Craig

People Hi,

this is an excellent thread.

IRRC the same resistor is also used on Discovery 1 (200 Tdi generation or

1989 up to 1995MY vehicles) Is this true?

Can such a replacement resistor as used on the RaRo Classic be also made to fit in a Defender (so as to gain a bit more control of the anemic factory heating and cooling fan?

Back to RaRo Cl. and Disco 200 where would it be more appropriate to fit the resistor? The standard factory position is to troublesome to access and fitting it somewhere more easily accessible would be nice. But can it be done? Is it only a matter of legthening the wires from the switch to the resistor?

---------------------

As for the sensitivity of Discovery 200, RaRo Cl and Defender vehicles to high electrical current systems we have a nice solution for the front (driving and high) lights on those models. A solution made in Greece but with excellent quality and a very easy "plug & play" configuration. It is a wiring harness with three connectors, a relay box, a fuse box and two wires and their round terminals (all supplied pre-assembled with just the wire terminals not crimped)

You unplug one of the factory female connectors (from the light cluster and bulb from the side where you will be fitting the new harness and its relay and fuse box) and you plug it to the pre-assembled male connector of the new wiring harness. You then route the electrical power feed wires (one red and one black in their protective sleeve) to the battery or your choise of electrical power supply and you connect them using the round terminal supplied with the kit. After you have made sure that everything is connected properly and securely you just plug the female connectors of the new wiring harness to the light clusters and plugs (one is already free since you have removed the factory female connector in step one. For the other side's light cluster and lamp you will have to also remove the factory female connector and fit the female connector of the new wiring harness to the bulb) The system provides electrical power from the selected source (here in Greece we prefer the battery) directly to the lights and therefore the high current bypasses the switch, factory fuse and the very thin wires of the factory wiring harness which especially on Defenders is a REAL and dangerous problem.

If anyone is interested for photos of the wiring harness I can post them. Just give me the URL of the public gallery that you want me to post them.

It is only a light relay with the wiring already made but it is not that expensive (actually it is on the cheap side) and it saves you from the hassle of cutting wires, crimping, the messy side of using electrical insulating tape everywhere etc. On Defenders the only thing required is to lengthen the electrical supply wires (black and red) so that they can reach the battery (if you decide to use the battery as the selected electrical source)

The loom was made available two weeks after I have fitted an old type relay to my 1993 CT Disco 200Tdi. But I bought a "plug & play" harness to fit to a friend's Defender and most probably I will be removing the relay from my Disco to fit the harness too.

We also found that OSRAM H4 55/60 Cool Blue bulbs give an excellent result as an upgrade from the simple Halogen bulbs and they are not expensive at all.

Reply to
Pantelis Giamarellos

Hi Pantelis

My original thought was to replace the resistors with a solid state solution in a location far removed from the heater assembly that would permit access without stripping the dash. I'm not sure that you can simply mount the resistors in a remote location without adding forced cooling. Others more knowledgeable should be along presently!

Cheers

Richard

Reply to
Richard Savage

Hi Craig

Yes, they're going back in the same place, although the replacements are a bit bigger.

The heater assembly is back together. Do you think that I'll be able get at the bearings without re-opening the case?

Cheers

Richard

Reply to
Richard Savage

In the RRC (that uses the Disco type matrix) and Disco200Tdi... From memory the blower motor and squirrel cage is mounted on the left side of the matrix to the tin plate at the top. Unscrewing the philips screws removes the whole motor/resistor assembly without physically spitting the matrix. The wiring loom, resistors, motor etc are all one piece that can't be separated without cutting wiring or plugs.

The motor doesn't have bearings, it has it's spindle running in brass bushes. Problem is that the grease dries, the spindle corrodes, and the fan gets damn tight (or seizes altogether) - thus drawing HEAPS more current and burning the wiring and switch.

I recommend dismantling the motor, cleaning the bushes & shaft and re-greasing it ...if you're comfortable with such an endeavour. A good buff of the shaft with some fine emery paper and kero is a good thing - make sure it's nice and bright and clean. It wouldn't hurt to do the same with your two A/C motors while you're in the mood. (If you have aircon, that is.)

--Craig.

Reply to
Craig

Check

Ditto

, the spindle corrodes, and the

more fun provided by LR :-)

Thanks Craig

I suppose that what you say makes sense - trouble is that it's freezing here and I doubt if SWMBO will let me bring the heater assy into the house. I'll have to wait until she is out!

Cheers

Richard

Reply to
Richard Savage

Solid State solution is fine. If using a linear transistor type solution, you will still need heatsinking and an air supply as the transistor just takes the place of the resistor value and still has to be able to dissipate the power to slow the motor. This means heat. This solution uses the transistor like a water tap - it has to do work to hold the current back from the motor. Doing work makes you hot.

A much tidier way would be a pulse-width-modulated approach, where the transistor is switched on and off at a frequency depending on the speed you want the motor to run. Since the transistor is switching the motor supply fully-on and then fully-off, then this means that the transistor isn't having to "get rid" of the excess power as heat.

A good experiment would be to use the trigger and control gear from the

12-14volt cordless drill that's busted and still laying in the corner of your garage. The trigger could be replaced with a potentiometer of comparable value. These are PWM controllers (you will hear the electronics squealing when you pull the trigger... that's the switching frequency).

Clear as mud?

As for lengthening the wires - remember to use thick ones - we're talking healthy current requirements here.

--Craig.

Reply to
Craig

Ironic isn't it - at the moment over here we'd have to do the same thing to keep from dying of heat exhaustion.

:-)

Reply to
Craig

Hi Craig

Where are you? My brother is in Adelaide and has had to move into a caravan (with A/C) as the a/c system has died in his house. He reports temperatures of 45degC

Richard

Reply to
Richard Savage

Hi Craig

As it happens I am having conversations with others about PWM control!

Richard

Reply to
Richard Savage

It wasn't like that in my RRC ('94 Tdi), the motor was only released by splitting the whole heater assembly as it was trapped between the two halves of the case and held by double sided sticky sponge tape, no screws either, just clips, and it actually had a sticker on it labelled 'Discovery'.

Which is what I did, but the motor had a brittle bakelite like housing on one end which you couldn't dismantle without damage and after cleaning and lubricating the shaft and bearings I had to hold it together with two strips of genuine bean tin, shaped to hook in two thin slots in the damaged housing and tack welded to the metal case. That was about six years ago and it's still running fine. As it is a major job removing the heater, I tried to buy a new one at £177 but was told they were obsolete, I thought they were supposed to keep spares available for at least ten years. I have since heard that Paddocks have a Bosch replacement for about £65.

Reply to
Oily

Hi Martin

Just what I want to hear after fighting the Famous Four 'almost but not quiet the same size as the original' heater matrix and four airflow flaps determined to flop in random directions into the case. Oh and don't forget riveting the fresh/recirculate flap back together. The fan seemed to spin happily while I was measuring V and I through/across the speed control resistors. Must I really take the fan out???

Richard

Reply to
Richard Savage

Hi Martin

Just what I want to hear after fighting the Famous Four 'almost but not quiet the same size as the original' heater matrix and four airflow flaps determined to flop in random directions into the case. Oh and don't forget riveting the fresh/recirculate flap back together. The fan seemed to spin happily while I was measuring V and I through/across the speed control resistors. Must I really take the fan out???

Richard

If it spins freely and quietly I don't think I'd bother but if you like lots of fiddling........:-)

As an addition to the thread I was looking at a friends RRC today and I noticed he had his heater resistor pack mounted on the offside inner wing near the top shock absorber mount to facilitate removal if necessary which was working satisfactorily. I don't think the resistance of the extra long wiring made any difference to it, it would be negligible anyway.

Reply to
Oily

Evening MArtin

Hmm. What to compare it with . . . . ? But I will look presently. Ice and snow have been replaced by rain such as the bloke with the boat would have been proud of!

I don't think I'd bother but if you like lots

The scratches on the backs of my hands have just started to heal. No reason why I shouldn't re-open them ;-)

Did you happen to notice how hot they became in normal use? When I tested mine they became too hot to hold without thought in the brief time I was running the fan. That is why I was thinking of fitting 50w replacements. Remote mounting is attractive for future replacement purposes but where to fit them so as to ensure best airflow will require some thought.

Cheers

Richard

Reply to
Richard Savage

Hmm. What to compare it with . . . . ? But I will look presently. Ice and snow have been replaced by rain such as the bloke with the boat would have been proud of!

I don't think I'd bother but if you like lots

The scratches on the backs of my hands have just started to heal. No reason why I shouldn't re-open them ;-)

LOL.

Did you happen to notice how hot they became in normal use?

I didn't, I was just looking at his LPG conversion. I don't suppose he did either as he said that they worked ok, so I wouldn't think he had bothered to check.

When I tested mine they became too hot to hold without thought in the brief time I was running the fan. That is why I was thinking of fitting 50w replacements. Remote mounting is attractive for future replacement purposes but where to fit them so as to ensure best airflow will require some thought.

Cheers

Richard

Reply to
Oily

I'm in south-east Queensland - it's not quite as hot, but with the odd rain it sure is humid.

--Craig

Reply to
Craig

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