Hi what size fuse should I use for a vdo temperature gauge I have the set up where it runs from the sump sender I have said before the bloody thing never goes above 50 degrees trying to trouble shoot it I have been using a 5 amp fuse for the light and a 5 amp fuse for the sender just wondered if this may be the problem any help appreciated
A 5-amp fuse in the switched live to the gauge is fine but if you have connected the light into the existing panel light circuit there is no need for a separate fuse. Current from the sender to the gauge is negligible and no need for a fuse.
The problem is most unlikely to be the fuse. How long are you running the engine to measure the temp?
If the needle doesnt move, check the gauge power is 12V with ignition on. Then pull the wire off the sender and check the wire has 12 volts on it. If not either the wiring has a break or the gauge is faulty. Theres also the fairly large number of permutations of stock temperature senders and stock gauges from VDO. Unless it was sold to you as a kit by a reputable dealer, its very likely that the parts dont match. However in this weather, the oil temperature is going to start off cold. If you do not have working air diversion flaps on your engine with a thermostat, it may never really ever warm up idling, and even with the flaps present, warm up will be slow at idle. On mine, about 5 minutes of driving at 30-40mph starts the temperature moving off 50C
^this. I reckon you've got a mismatched gauge and sender. If you're up for it, take the sender out and get a hot air gun on it to see what the gauge does.
Looking at the OP other threads on the same subject it appears the gauge and sender are both 0-150, so it should work. But it’s not obvious whether the engine isn’t heating up or the gauge isn’t working and I don’t think the oil temperature has actually been measured. Hot air or boiling water won’t do anything unless the sender is earthed, will it?
Damned awkward if it's a sump sender but it's the best sanity check. Catch the oil in something clean so you can reuse it.
Thanks every one ..so probably the 5amp fuse I had was fine...I drove all the way from Loch lomond to the wirral once and the bloody thing only just got above 50...nd the entire width of England...I changed the sump sender incase it was that...I used a really thin wire that came in the jk kit...so changed it to a 16 gauge wire as recommended that never worked I have tested the gauge by reversing the current and it shoots up to 150....so am out of ideas I will try a new gauge at some point last resort...i have earthed the gauge to the van...then I changed it to the earthing block behind the main gauge panel ...that never worked...I will take it for a long drive In the spring and report back thanks for the help any way if not I will throw it over the fence ha
Well, why don't you do as suggested and check using a mug of boiling water, then you'd know. Honestly can't understand why you haven't done this rather than faff about changing cables etc.
The way it works, the sender resistance even when hot is much higher even than many kinds of thin wire.. so the supplied thin wire results in maybe a slightly low reading. In the region of a line width on the gauge. A kilometre of 0.5mm2 copper wire has a resistance of 34.5 ohms.. (Theres a lot of random electrical beliefs recited by people trained as parrot level technicians in the US military) I believe the resistance against temperature table top row is correct. The corresponding gauge part numbers are listed alongside. Grounding the sender wire though 62 ohms instead of the sender should result in the indication of 100C . Alternatively the sender in boiling water should have a DC resistance of about 62 ohms. Whip it out stuff in a 14mm sump plug to minimise oil loss or a spark plug.. Any inconsistency .. decide which is incorrect and replace.
Mine I can drive 50 miles this time of year and it barely warms up. I had another sender previously where I accidentally cracked the porcelain and that was very erratic.
