Anonymous

Fan Control Change

Here’s where to discuss anything specific about your standard(ish) car or something that applies to the model in general.
Post Reply
UKPhilTR7
TRiffic
Posts: 1931
Joined: 24 Mar 2005 12:52
Location: West Midlands, England

Fan Control Change

Postby UKPhilTR7 » 02 May 2021 22:19

Over the weekend I replaced the fan controller on my 2lt 7. The on that I had on was going as there was a bad connection and sometimes the fan came on and then sometimes it would not until I moved the cables on it. So I thought it time to change it.

I got one of the Revotec controllers that came with a new relay, so replaced all the old with the new. All went OK, but I previously has two cables going to to the fan, but now I have one. That is OK as they boch did the same thing when a power supply was connected.

So, new controller in (not much coolant lost) as on the top hose, all wired up and the car running up to temperature. Previously on the old fan controller the fan would kick in at half on the gauge and stay on until the original gauge needle went to 1/4.

So when setting the new controller up, I waited till the gauge got to 1/2 and was about to turn the fan on. However, then (as the expansion tank cap was off) she started boiling out of the tank and going out of the overflow pipe.

Was this just due to the fact that the cap was off or was there something more serious going on? I do not think it was a bubble as did not empty her out.

I am replacing the gauge sensor and the thermostat, change things over before I put new coolant in.

I am going to flush her but was wondering what position on your dash temp gauge your car runs at? Mine is just standing still at the moment, but if she was running with the air flowing through, would you expect her not to go past 1/4 on the gauge?
Image

saabfast
TRiffic
Posts: 1936
Joined: 03 Feb 2006 08:17
Location: Bexhill-on-Sea

Re: Fan Control Change

Postby saabfast » 02 May 2021 23:52

Is the fan controller not adjustable?
I changed to an electric fan when the original got noisy. I have the controller set so that it comes on at just below half on the gauge and switches off at just above 1/4. (With the original fan it always ran at between 1/4 and 1/2, mainly just above 1/4 unless in heavy traffic congestion on a hot day).
You system could be boiling due to not having the rad cap on as the cap allows the system to pressurise and run hotter without boiling (ie raises the boiling point). You do still need to go through squeezing the top hoses prior to putting the cap on though to get all air out of the system.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
Image

Hasbeen
TRemendous
Posts: 6474
Joined: 28 Apr 2005 12:32
Location: Australia
Contact:

Re: Fan Control Change

Postby Hasbeen » 03 May 2021 06:10

I don't believe the tank fitted to the 7 is an expansion tank, I believe it is a simple remote header tank.

I never liked the fact that my 7s water level stabilised at about 2.5" below the filler cap, as this is below the highest point of the cooling system. When we retired a Toyota Cressida I fitted it's expansion tank to the 7. It fits perfectly beside the radiator on the inner guard, filling the gap previously somewhat closed by a waxed cardboard panel.

With a redrawing radiator cap the level has now stabilised at less than an inch below the filler cap. The car has not ever required a coolant top up since I fitted this, other than at a couple of coolant changes over the last 5 years.

Hasbeen

FI Spyder
TRemendous
Posts: 8915
Joined: 03 Jul 2006 19:54
Location: Canada

Re: Fan Control Change

Postby FI Spyder » 10 May 2021 15:11

Whatever it's called the difference between when the system is hot such that expanded coolant flows out of the overflow tube and when the system is cool and the contracted coolant is below the point where the low sensor turns on the light on the dash (1980 and later) isn't very much. I do get a warning sign however as when I go up my steep driveway the low coolant light will turn on and then go out when I am horizontal again. Where the temperature needle should sit is like asking how long is a piece of string. As the gauge is analogue, it depends on the resistance in the circuit and other things. Any poor/bad connections in the circuit, from where it gets the 12V current to where it grounds it to complete the circuit, will raise the resistance. Depends on the characteristics of the particular heat sensor, same with the gauge, The voltage of the system (alternator, etc.).
- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 2013 Volt - Yellow TCT

dursleyman
TRiffic
Posts: 1571
Joined: 11 Jun 2007 22:55
Location: United Kingdom
Contact:

Re: Fan Control Change

Postby dursleyman » 21 May 2021 14:07

I have a Revotec on mine and set it to come on just below half way on the gauge. It usually runs at just over the quarter mark.
Russ

1981 TR7 Sprint DHC & 1977 TR7 Sprint FHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

Image Image

busheytrader
TRemendous
Posts: 3145
Joined: 14 Oct 2007 17:49
Location: United Kingdom
Contact:

Re: Fan Control Change

Postby busheytrader » 26 Jun 2021 14:43

FI Spyder wrote:Where the temperature needle should sit is like asking how long is a piece of string. As the gauge is analogue, it depends on the resistance in the circuit and other things. Any poor/bad connections in the circuit, from where it gets the 12V current to where it grounds it to complete the circuit, will raise the resistance.


Agreed. I removed the capillary adjustable fan controller on mine and replaced it with a fixed temperature on / off switch screwed in to an in-line housing. 95c on and 85c off electric fan control, combined with a 82c coolant thermostat, an aluminium radiator and a new coolant sensor. It’s a V8.

Instead of looking at the gauge for the temperature, I calibrated the gauge from the thermostat’s opening point and the electric fan’s activation. At a steady 40mph on a cold day the gauge holds steady around the 1/4 mark (82c). At about the needle’s width from touching halfway, the electric fan is switched on (95c). If idling whilst stationery, it can take about 60 to 90 seconds for the temperature to fall to the switched off temperature (85c), at about a needles width off the 1/4 mark.

I changed to a fixed temperature switch as I was fed up with the hose weeping around the previous capillary tube. Today’s thinner walled radiator hoses don’t seal as well around it.

stevie_a
TRemendous
Posts: 3325
Joined: 19 Jun 2005 10:28
Location: Glasgow'ish

Re: Fan Control Change

Postby stevie_a » 26 Jun 2021 22:00

.


.For years I had an adjustable thermostat with the gauge (aftermarket not TR7) needle sat half way fan came on just a needle width over half and off a needle width before half.
TimePhoto_20190512_125530.a76ef047d8d24c03823acdf41c4ee7c8.jpg
TimePhoto_20190512_125530.a76ef047d8d24c03823acdf41c4ee7c8.jpg (79.25 KiB) Viewed 5964 times

But when I put a brand new old stock dash in and decided to change to a fixed 95c on and 85c off and attached it to the radiator.
20210409_105316.jpg
20210409_105316.jpg (140.1 KiB) Viewed 5964 times


Now the needle sits either side of the quarter.
I would love it sit half way again.
Is there a way to adjust the gauge?
Attachments
20210501_094124.jpg
20210501_094124.jpg (53.67 KiB) Viewed 5964 times
If it's not broke don't fix it.

saabfast
TRiffic
Posts: 1936
Joined: 03 Feb 2006 08:17
Location: Bexhill-on-Sea

Re: Fan Control Change

Postby saabfast » 27 Jun 2021 08:51

Have you tried changing the gauge sender to see if that makes a difference?

Mine almost failed altogether and was getting dodgy and erratic so I changed it and it was back to running with the needle between quarter and half as most originals seem to be. When I changed to an electric fan with capillary sensor (adjustable) I set it to switch on at just under the half and it switches off at just over the quarter. I have never checked the actual temperatures but just replicated as close as possible the original running temperatures.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
Image

stevie_a
TRemendous
Posts: 3325
Joined: 19 Jun 2005 10:28
Location: Glasgow'ish

Re: Fan Control Change

Postby stevie_a » 27 Jun 2021 11:34

.

Yes i have actually tried 3 different ones :D
If it's not broke don't fix it.

Beans
TRemendous
Posts: 7788
Joined: 15 Mar 2006 19:29
Location: Netherlands
Contact:

Re: Fan Control Change

Postby Beans » 27 Jun 2021 17:10

Did you measure the actual temperatures?
Image
1976 TR7 FHC (currently being restored ...)
1980 TR7 DHC (my first car, a.k.a. Kermette)
1981 TR7 FHC (Sprint engined a.k.a. 't Kreng)

http://www.tr7beans.blogspot.com/

Hasbeen
TRemendous
Posts: 6474
Joined: 28 Apr 2005 12:32
Location: Australia
Contact:

Re: Fan Control Change

Postby Hasbeen » 28 Jun 2021 00:53

In normal running, hot day/cold day, [33C/15C] Air conditioning on or off, my 7 sits at a needle width above 1/4.

This is with everything stock, radiator, fan, water pump & thermostat but all new 5 years ago when the engine was rebuilt. The only non stock feature is the overflow bottle, which keeps the coolant about 2" higher in the header tank than without it.

That reading is given when the top of the radiator reads 89C on my infer red hand held temp gauge. I can only assume it is the thermostat controlling the system, as it should if the system is adequate & in good condition.

The 4.6L 8 had really bad problems in heavy traffic, despite a big 4 core alloy radiator big fans front & rear of the radiator & all the rest. No problem when being driver really hard, or out in the country cruising.

Finally traced to running very lean at low throttle openings at low revs. It was perfect up top end as tuned on a dyno. With the mixture tuning fixed, no further trouble.

Hasbeen

Post Reply

Who is online

Users browsing this forum: No registered users and 31 guests

cron