Temperamental Temp Light

An alchemy of sparks, copper wire and earth

Moderators: User administrators, Moderators

Post Reply
Posts: 744
Joined: 10 Aug 2019, 23:30
80-90 Mem No: 17004
Location: Coventry

Temperamental Temp Light

Post by Stesaw »

Right, Story time.

The other week after coming back from a local garden centre I had the temp light start flashing about 2 miles from home...ruh roh.. glanced out the back and saw smoke billowing out. Pulled over to find a heater core coolant pipe had split on me. Luckily it had split right on the end so I cut the pipe down and put it back on. I carry coolant and water so topped back up did a quick bleed check and off I went, temp light flashing and flickering, got back and checked pipes all hot, radiator was evenly warm and coolant tanks were as they should be. Left it to cool and checked the tanks again no change.  

I haven't heard my rad fan come on in ages, maybe because it's been cold but I got thinking maybe something was up with the fan or electrics/thermoswitch as it might be causing the light to come on now and then as the van was running hotter than it should be. Looked up on the forums and did the test on the thermo switch connector by bridging the connections, fan didn't spin. Hmm OK that won't do. There are two relays above my fuse box. Took both out and luckily due to the syncro I have spares. Sadly the smaller relay from the syncro had bigger spades on it so I couldn't plop that into the holder so I put the other one back in. The other relay has number 43 stamped on it which I swapped over and tried the fan again, success both speeds came on.

After ordering and replacing a couple of pipes and the junction box (yes I broke the old one removing the knackered pipe) I made sure the system was bled took the van out again today to the garden centre. The temp needle usually sits about half way covering the LED if I have the heaters on and a bit higher with them off. As it's been a nice day today I had the heaters off, but the light started to flash every now and then, sometimes on off as it should and others just a flicker. 

So put both heaters on and the temp went down to about half with no light flashing for a bit then I'd notice the light flash maybe once or twice with the temp settling over the LED. Got to the Garden centre and checked the rad, was very hot all over no cool spots, pipes were all hot, both rear heater and front heaters blowing hot air just fine. Checked the coolant tanks in the back both full as they should be, so I doubt there is an airlock. However as the rad fan never came on I thought it could be overheating.

Got back home with the heaters on and the occasional light flickering/flashing, no rad fan coming on. As I knew the fan was OK maybe the thermoswitch was duff? So when I got back I plugged the thermoswitch from the syncro into the wiring and plonked it in a saucepan of water on my little stove. Both speeds of the fan came on, OK, quickly swapped them over and tested the one out of the rad. That also worked fine fan came on both speeds :roll: . So I guess the van wasn't getting hot enough to get the fan on. I just left the syncro one in for now and re-bled and topped up the system.
When messing around in the drivers seat I tapped the dash cluster and the temp light flashed.  :roll: So I guess something must be shorting when driving along as well causing it to flash and making me think the vans overheating. Obviously with recent happenings with the van I wanted to make sure I wasn't overheating. Maybe the temp light shorting is the issue and the van didn't get hot enough for the fan to kick in. But at least now I know my fan does work!

So, maybe I need to invest in a replacement harness for the gauges / lights?. Unless it's the gauge itself?
1985 LeisureDrive 1.9DG 5 Speed- Syncro project.. soon.. ish..
1987 Syncro JX- Donor

User avatar
Posts: 1096
Joined: 22 Nov 2007, 19:22
80-90 Mem No: 4709
Location: Upwell, Norfolk

Re: Temperamental Temp Light

Post by AngeloEvs »

If the Temp Gauge LED can be triggered by tapping the dash it may be anyof the following:

Poor connection of the regulator in the regulator socket.

Poor connections or loose  nuts that secure the temp gauge to the ribbon

Poor or faulty  connection at the 14 way Dash Multiconnector

Could be a faulty gauge but usually the problem is a capacitor in the gauge and it would not be an intermittent fault

Dash removal, inspection and testing is the best solution, the latter may not be possible without the correct Test equipment but you be able to verify the condition of the ribbon and wether the reguator looks tarnished/oxidised.
1987 DG Karisma LPG with remodelled interior

Post Reply