Diagnosis

Sunday
Took the car for a 90 mile drive on Sunday, ambient temp was ~10C (=50F). (Cardboard blocking still in place).
Engine came up to temp within 5 minutes. After 15 minutes I started playing with the heater control, this is what I found:
Heater knob pulled fully out: Indicated temp drops to ~60C within ~5 minutes.
Heater knob pushed fully in: Indicated temp rises to ~90C within ~15 seconds.
Heater knob halfway: Indicated temp maintains at ~90C. Some heat coming out, not enough to keep warm without jacket & gloves.

Conclusion: I think at the full out position, the heater valve is actually closing & letting nothing through.

I re-confirmed my plumbing and it is definitely connected like figure 87 in the build manual.

Also, while out, I noted that the Speedo behaved fine. This means that either the extra ground connection fixed the problem or, the speedo did not get hot enough to start failing.

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Cool……not

Early this morning, the ambient temp was 3C ( = 37F), I went for a test drive.
Indicated temp reached 80C at 5 minutes and 88C at 5.5 minutes and pretty much held steady at the ~90C +- for the next 5 minutes.
Then I fully opened the heater valve and turned on the heater fan and within 1 minute the indicated temp dropped to 60C.
I closed the heater valve and the indicated temp came back to ~90 within 20 seconds.
I tried different heater valve settings, and could maintain ~90C at 1/4 open or less.
However, I put my hand at the heater outlet and noted that the air output is pretty cool (not warm), but above 37F.

So, I’m concluding that a heater on a 7 is pretty worthless if it only works in hot weather.
Also, the radiator & oil cooler seem like overkill and that a radiator core the size of the heater is sufficient, and even then, its not necessary to put it into the airflow.
I wonder if there are other options for a heater – ie: electric heater. Has anyone tried.
In the meantime, I willl just have to dress in my ski clothes……….

Technical update

The Speedometer Issue
Last time, I had concluded the speedometer was bad on account of when it went intermitant, a shot of freeze spray returned it to usefulness, at least for a few minutes. A faulty chip inside was my diagnosis. Caterham believed my story & sent me a new speedo, which I fitted & calibrated. And, it worked fine for 60 over miles- then proceeded to go intermitant.
Further input from Sean (CA Caterham Club) suggested that it was a bad ground to the instrument panel common grounding – which is bolted to the wiper motor mount on the LHS under the dash. I checked, read 1.4 ohms to the battery -ve. So I ran an extra wire from the battery -ve to the instrument panel common ground.
Yet to test it – stay tuned.

Over Cooling
After the chilly ride home on Saturday, I’m looking to get the heater working in cold weather. The problem seems to be that although the engine maintains a temperature of ~95c, when I turn on the heater, it provides extra cooling to the engine and the temperature drops to ~60C.
I got advice from Magnus & Doug (CA Caterham Club) to check out the thermostat.

FYI, here is my plumbing diagram……
7plumbing

I did a static test in the garage. Started the engine and set to 2400 rpm.
Indicated 60C Radiator cold
Indicated 70C Radiator cold
Indicated 75C Radiator cold
Indicated 80C Radiator cold
Indicated 88C Radiator starting to get warm at radiator top – this was about 5 minutes
Indicated 90C & holding
After another ~ 5 mins bottom radiator getting hot
Indicated 98C Fan on for ~ 1 minute
Indicated 98C Fan off
Indicated 98C Fan cycling on for ~ 1 minute each time
End of run.

Conclusion: the thermostat is working and opening at 88C.

After discussion with Magnus & Doug, we concluded:
-Oil cooler will have a significant cooling impact.
-An oil cooler thermostat should be investigated.
-Blocking off part of the radiator and all of the oil cooler in winter.
-The thermostat maybe opening at 88C, but what temp does it close?

So, I have blanked off part of the radiator for a test – see picture.

Cardboard blanking on radiator & oil cooler to prevent over-cooling in winter

Cardboard blanking on radiator & oil cooler to prevent over-cooling in winter

The Journey home

Being optimistic we left topless, which was fine until we hit slow traffic getting off 880 onto Mission Blvd and got thoroughly soaked. So we stopped & put the top on. Sunny in Walnut creek, so we took the top back off & drove to Auburn for dinner. Top back on then home via 49N & 20E & onto I80 for a few miles then onto Old Hwy 40. By this time it had started snowing and we wanted to keep off I80 & the chain control. By the time we got to Soda Springs we were driving in the 2 cleared ruts with ~6″ of snow in the middle, which found its way via the sump into the front of the engine & horns etc. The engine started cutting out – I think that may have been water in the electrics, but managed to keep going in 1st gear through the thick of it. Finally got home cold & wet by 9:30pm.

Snow still in the engine the next morning.

Snow still in the engine the next morning.

Snow still dripping out

Snow still dripping out

Looking a bit dirty

Looking a bit dirty

Snow came in around the door

Snow came in around the door

Arrived home and cleared the snow out of the door panels

Arrived home and cleared the snow out of the door panels

California Caterham Club Picnic

Good to meet everyone at last after months of reading the CCC forum. Dot & I had a great time. We also had an adventure getting home.

Sean, middle, Jeff & Julie Hamlin in foreground and Raul at back

Sean, middle, Jeff & Julie Hamlin in foreground and Raul at back

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7's lined up

7’s lined up

Tom Jones from Santa Cruz

Tom Jones from Santa Cruz

Driver?

Driver?

This one belongs to Larry & Goya

This one belongs to Larry & Goya

I think this is Sean's

I think this is Sean’s

Driver?

Driver?

This is Lucy Cate, belonging to the Hamlins

This is Lucy Cate, belonging to the Hamlins

This one belongs to Raul

This one belongs to Raul

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7's lined up

7’s lined up

More 7'sMore 7’s

7 owners, Dave,---,Raul,---

7 owners, Dave,—,Raul,—

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7 Line up in Vasona Park

7 Line up in Vasona Park