Gold and silver resistors - Page 7

Roverlike · 19th August 2018, 15:06

Quote:

Originally Posted by MarkS

Ok. Signed in. Sorry, the images are blurred. I've cleaned my glasses, so it must be the images. Any chance of better images, Roverlike ?
PS Are the low speed and high speed relays mounted next to the fan ?

PM me your email address and I will send you better pictures. Relays,are within black control box which is usualy mounted close to the fan, unless someone mounted it away of fan, but easier to access it.

EDIT: I uploaded better pictures as .pdf attachments.

.

MarkS · 21st August 2018, 17:06

Has anybody actually measured the current drawn by the 450W fan on slow speed ?

SD1too · 21st August 2018, 17:36

That would be very difficult to do Mark. A clamp ammeter would be the best way particularly in view of the high current surge when the fan first starts. The slow speed (large) TE relay V23134 has a "limiting making current" of 120 amps and a continuous current at 85°C of 40 amps (falling to 17 amps at 125°C). So as you can see the relay specification is satisfactory for the load and so it's very unlikely to fail.

Simon

WillyHeckaslike · 21st August 2018, 18:04

I think the thermal fuse inside the oem resistors was/is the main source of failure with them. The generics don't have that fuse and while the incidence of failure seems to have reduced as a result there have been a small but nonetheless worrying number of failures which some have attributed to moisture ingress but ... could they be wrong? Maybe Rover got it right with the thermal fuse and maybe not so on the wattage. Hmm?

HarryM1BYT · 22nd August 2018, 19:51

Quote:

Originally Posted by WillyHeckaslike

The generics don't have that fuse and while the incidence of failure seems to have reduced as a result there have been a small but nonetheless worrying number of failures which some have attributed to moisture ingress but ... could they be wrong?

Those gold resistors where never designed to survive a driven rain environment so rain could perhaps leak into a few. Those who have reported the gold ones to fail, have reported them as exploding. The exploding suggests high pressure built up, which I doubt would be likely to occur with a simple resistor element failure. 75w of heat in a tightly confined wet space, would turn the wet to instant steam and a lot of pressure.

T-Cut · 23rd August 2018, 09:57

Quote:

Originally Posted by WillyHeckaslike

- - - -there have been a small but nonetheless worrying number of failures - - -

When you look at the statistics, it's probably no higher than would be expected. Failures attract more attention. I remember reading a post by Jules (who must have fitted more than anyone anywhere), reported a failure rate of two in a thousand (I'll try to locate his report). Not all of these involved rain. So, a 0.2% failure rate in a heavy duty application like the fan circuit seems pretty good to me. It's far lower than road spring breakage, for which there are hundreds of reports.

TC

MarkS · 19th October 2019, 00:53

FYI I finally got round to repairing my blown silver resistor.
In the end, I used a pair of 0.25ohm 100W resistors in series.

Why not 2 X 1ohm in parallel ?

Because if one blew open circuit, it would leave one resistor left in circuit, which may seriously overheat and possibly catch fire. But with two resistors in series, if one blows open circuit, then the other resistor is safe.

I also down-rated the fuse FL4 from 80amp to 50amp.

We will see what happens.

So far it's survived one rain storm.

Steve Rowden · 15th August 2020, 10:51

Can anyone tell me where the 2 resistors are mounted on the 2.0 cdti please. Thanks

suzublu · 15th August 2020, 11:02

Quote:

Originally Posted by Steve Rowden

Can anyone tell me where the 2 resistors are mounted on the 2.0 cdti please. Thanks

Look through the front grill at the fan behind, depending on which type you have, a resistor, if fitted, should be visible at the 2 o'clock position
https://the75andztclub.co.uk/forum/s...d.php?t=120113

T-Cut · 15th August 2020, 11:18

Quote:

Originally Posted by Steve Rowden

Can anyone tell me where the 2 resistors are mounted on the 2.0 cdti please. Thanks

They're fitted to later models and there's only one. It may be the original aluminium/'silver' version or the uprated/aftermarket/'gold' type.
The original/silver resistors are under-rated for the job and most failed pretty quickly. A very few may still be hanging in there, but the majority will have failed and many of those replaced with the 'gold' type. You can get these from 75/ZT traders, from eBay or electronics outlets like Farnell.

TC

21st August 2018, 17:36	#63
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,375 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	That would be very difficult to do Mark. A clamp ammeter would be the best way particularly in view of the high current surge when the fan first starts. The slow speed (large) TE relay V23134 has a "limiting making current" of 120 amps and a continuous current at 85°C of 40 amps (falling to 17 amps at 125°C). So as you can see the relay specification is satisfactory for the load and so it's very unlikely to fail. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

15th August 2020, 10:51	#68
Steve Rowden Newbie Rover 75 Saloon Join Date: Dec 2014 Location: Margate Kent Posts: 7 Thanks: 0 Thanked 0 Times in 0 Posts	Gold/Silver resistors Can anyone tell me where the 2 resistors are mounted on the 2.0 cdti please. Thanks

21st August 2018, 17:06	#62
MarkS Gets stuck in Rover 75 Diesel Tourer, called Perseverance Join Date: Nov 2011 Location: Bournemouth Posts: 664 Thanks: 189 Thanked 157 Times in 108 Posts	Has anybody actually measured the current drawn by the 450W fan on slow speed ?

21st August 2018, 18:04	#64
WillyHeckaslike This is my second home Rovers 75 & 25 Join Date: Oct 2010 Location: Wearside Posts: 4,522 Thanks: 543 Thanked 709 Times in 511 Posts	I think the thermal fuse inside the oem resistors was/is the main source of failure with them. The generics don't have that fuse and while the incidence of failure seems to have reduced as a result there have been a small but nonetheless worrying number of failures which some have attributed to moisture ingress but ... could they be wrong? Maybe Rover got it right with the thermal fuse and maybe not so on the wattage. Hmm?

19th October 2019, 00:53	#67
MarkS Gets stuck in Rover 75 Diesel Tourer, called Perseverance Join Date: Nov 2011 Location: Bournemouth Posts: 664 Thanks: 189 Thanked 157 Times in 108 Posts	FYI I finally got round to repairing my blown silver resistor. In the end, I used a pair of 0.25ohm 100W resistors in series. Why not 2 X 1ohm in parallel ? Because if one blew open circuit, it would leave one resistor left in circuit, which may seriously overheat and possibly catch fire. But with two resistors in series, if one blows open circuit, then the other resistor is safe. I also down-rated the fuse FL4 from 80amp to 50amp. We will see what happens. So far it's survived one rain storm.