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MG Midget and Sprite Technical - I/D of GRH509 top hose

Does anyone know what the internal diameter of the top hose (GRH509) for a cross flow radiator by any chance?
It's the one I don't have a spare for of course :(
The Revotech thermostatic switch has packed in and I'm not prepared to pay what they're asking for a new one so am looking at something like this

https://tinyurl.com/56atatrc

but need to know which size to choose.
In the meantime there's a manual override switch, just in case.



Jeremy MkIII

The Revotec MG midget X-Flow - 1275cc, Part number: B-SMG 1275, Cooling Kit use a 25mm Revotec Electronic fan controller which is about 25mm (1" in old money). - https://www.revotec.com/acatalog/Negative-Earth-1.html

Are you sure its the Revotec Electronic Fan Controller Hose Fitting at fault and not, if previously combined fitting of the wiring or the dog and bark yourself override switch or installation. - https://www.revotec.com/acatalog/Electronic-Fan-Controller-Hose-Fitting.html


Nigel Atkins

My Revotec controller died after about 10 years, it started switching the fan on earlier and earlier despite adjusting it. After a while the fan was just constantly on.

I just replaced it with another as I like the design, it’s been fine for about 5 years.
John Payne

I was looking at those, but my radiator is a downflow one and there is not enough length of hose to cut and insert the switch. You will probably be OK with the crossflow rad.
Bernie.

b higginson

Thanks for that link Nigel. 25mm it is then.

Both have worked well for about 10 years (seems a common theme emerging there John) when the controller failed to cut in and no amount of adjustment could cajole it back into life. Fortunately having the override switch wired in saved the day.

Bernie, in the link Nigel kindly provided, there is a kit for the vertical flow radiator - Part number: B-SMG VERT.
Jeremy MkIII

Now, obviously, my replacement wasn't as straightforward because it's me and my car.

The controller lasted just under 9 years, I can't remember how it played up, how can I remember when on my car so much goes wrong so often.

I bought the replacement controller direct from Revotec but when I fitted it it seemed to have a pre-starting stutter. Revotec asked about the wiring and earthing so to prove the point I took direct feeds off the battery clamps. Then they said it could be interference off the ignition so I changed my HT lead set. Then they said I must be one of the 1 in 5,000 that gets interference and I'd needed the original electronics and they'd make me one and send it. That then worked. I guess they use a different design now or cheaper material and/or cheaper made than when I originally bought my fan kit.

That's another story. I bought the original fan kit from a supplier and to cut a longer story short the fan in the kit was a sucking instead of a blowing. Revotec said this wasn't possible as they were so careful at packing the kits, after I stood on my head with a magnifying glass to read the upside down label on the fan through the grille and gave them the number they believed me and sent me the correct fan, to their credit, that arrived the next day, so yet another drain down and removing of rad and shroud.

I later swapped the original fan for one of their higher powered fans as my car is modestly uprated, I should have used wingnuts on the radiator bits.

Nigel Atkins

That's quite a faff for you Nigel and then having to uprate it - oh dear; glutton for punishment?
The ebay seller has replied already (on a Sunday evening), the 26mm version is unavailable for about 4-6 weeks so I'll wait.
Jeremy MkIII

Jeremy,
I also saw them at the NEC but that another story, I bet most of the stuff will be in the Archives here.

I don't know if they did back then but certainly now they have on their site "Please note: Revotec Retrofit cooling kits are designed to work with standard unmodified vehicles." Of course is it against the law for certain men to read instructions so they'll moan about it later, and not their fault as they're above the need to read anything.

I was wondering if your electric fan is to supplement your engine driven fan and if not what temperature switch you'd select to to tie in with your water stat and it's possible variance.
Nigel Atkins

Instructions are for wimps (until it all goes horribly wrong).

The engine fan has been ditched so the electric fan only came on once the temp got beyond normal.

The choice of temperature is between 80 and 95 degrees so I've plumped for 85 as being just on the slightly warmer side of the standard thermostat.


Jeremy MkIII

Jeremy,
please don't read the following until you have ordered and fitted your switch - in fact to prevent any accusations of you being a wimp I won't post it until you've fitted the switch.

I don't mind being called a wimp, I'm too wimpy to reply and defend myself anyway.
Nigel Atkins

Jeremy look away now!



‘Water’ thermostat temperature range

The rating on a ‘water’ thermostat is a nominal temperature at which it starts to open (not when fully open).

As an example, with info from just one manufacturer – a 180f water stat may have a +/- 3f tolerance so starts to open at between 177f-183f. The stat is fully open about 15f-20f degrees above its rated temperature, so fully open at 192f-203f.

180F stat - starts to open 177f-183f - fully open 192f-203f

82c stat - starts to open* 80.5c-84c - fully open* 89c-95c (* to nearest 0.5c)




Nigel Atkins

Jeremy, have you found the website of the folk that do the kits on eBay? Lots of advice on there:

https://shop.stoneyracing.com/universal-thermal-radiator-fan-switch-adapter-kit/

They recommend a 95 deg switch for an 82 deg thermostat (assuming that is what you are using?). That is what I am using on my 1500 and it seems to work well, only coming on when the car is stationary for a couple of minutes. I think an 85 deg switch would cause your fan to be on nearly all the time as the off temperature (80 deg) is below that of the thermostat temperature.

Malc.
Malcolm

If you believe the figures I found then the thermostat may not be fully open until 89c-95c (to the nearest 0.5c).

The link Malc put up has "A good rule of thumb is that the on temperature of the switch should be around 12°C to 18°C higher than the vehicles rated thermostat opening temperature i.e. the temp the thermostat begins to open at."

Doesn't say if this is for road or race or both.

82c stat - starts to open* 80.5c-84c - fully open* 89c-95c (* to nearest 0.5c)

The ± 3°C of the switch gives a range of -

. 85c - ON 82-88c - OFF 72c-78c

. 95c - ON 92c-98c - OFF 82c-88c

. 100c - ON 97c-103c - OFF 87c-93c.

As there was a (variable) switch before I'd go with the distance of the gauge needle the previous switch cut in at from where the needle is normally at when the engine is fully warmed and going at a steady speed of 40mph+ on an open road (ignoring any gauge figures if they are on the gauge). Depends how 'hot' or not or 'cold' or not your engine normally runs at.
Nigel Atkins

Jeremy. Thanks for the info regarding the down flow version, but I already have an electric fan (Kenlowe) but the switch is somewhat a Heath Robinson affair with a bulb in the hose and a capillary tube. So, I just wanted an alternative switch, but the short right angled top hose made it impossible to fit the aluminium tube type switch. However, I noticed the one that goes through the hose, and after watching the fitting video, I’m sure it will fit. A bit expensive, but at least if I need to remove the top hose for any reason, the switch is not disturbed, unlike my current one.
Bernie.
b higginson

I just ordered the Revotec self sealing switch and an override switch, so, if anyone is interested, I’ll report back once I’ve fitted it. My wallet is having a lie down.😬
Bernie.
b higginson

Thanks for the good advice Nigel and for the link Malc.

Looks like a 95 degree on to give an 85 degree off as you say Malc, will do the business. Just as well they were out of stock as I'd have ordered the wrong temp.
Never to old to learn, eh! :)

Glad you're sorted Bernie - even if it came at a price; it's still a lot cheaper than an overheated engine.
Jeremy MkIII

Jeremy,
it'd be interesting to know if your fan cuts in more often or less often with the new switch based on where your gauge needle showed with the Revotec switch and shows with the new switch, based on where you set the Revotec switch to cut in (if that makes sense(?)).
Nigel Atkins

Ok Nigel, will see what happens when the new switch arrives (4-6 weeks) and is fitted. I set the Revotech to come on just after the needle cleared N. Suspect this may run a little hotter but we'll see.
Jeremy MkIII

Thanks Jeremy. I don't like my needle to be too close to the N as it's normally so far before it. I tried setting to come on just after the 'N' but I never felt comfortable with it there, same with the 88c water stat, just never felt fully at ease with it.


Nigel Atkins

I bought the Revotec thermostatic switch that seals through the hose and it works perfectly. Very easy to get the adjustment right.

Just got to fit the override switch, which looks easy enough to do.

Bernie.
b higginson

This thread was discussed between 10/04/2022 and 22/04/2022

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.