Minor Electrical hassles
Wednesday, November 12th, 2008
I had two recent problems with the 109’s electrics - the horn and the driver’s seat heater stopped working (not simultaneously).
The seat took a lot of tracking down with an electrical probe and continuity tester to find the fault - a problem in the earth part of the seat’s back pad. Each seat has two pads, one for the base and one for the back, each with two heater element loops (so four loops per seat). The loops are connected in parallel and series, ie. each loop in the base in series with a loop in the back, with the “double loops” operated independently. One pair comes on with the low heat setting, and both pairs are active when high heat is selected (where you have two settings available). The earth ends of both loops in the seat’s back pad join together as a common earth, and then enter the 65oC thermostatic switch (a metal sleeved unit about 3/4″ long, 1/4″ wide and 1/8″ thick) which is embedded between the elements. A break in a single loop will still allow the other pair to operate, so if the low heat loop circuit is broken anywhere, the second loop should still produce heat when “high” is selected, though it will only produce a single loop’s low output. If the “high” loop is broken, then the same low heat will be produced regardless of the “low” or “high” selection.
I don’t know how hot these pads get when on high, but the thermostatic switch is probably an important safety element, if for no other reason than to prevent a fire if the seat is inadvertantly left on without being occupied, so they shouldn’t be bypassed. Initial tests showed a failure of the thermostatic switch, and I spent several hours trying to source a replacement. A local electrical shop ended up giving me a few electric motor overheat protection switches, but testing them at home before fitting proved these were simply thermal fuses. However, a new test of the “failed” switch (now cut out of the circuit) showed it was conducting, so that meant the switch was actually serviceable and there had to be a hidden break in a common earth wire near the switch. Once this was found, the switch was soldered back in and the seat reassembled. It all works properly again, at no cost other than a few wasted hours.
The horn failure was also initially misleading. I started off by using my electrical probe to detect current at the end of the positive wire to the horns with the switch pressed - nothing. I next tried the contact where the indicator stalk wiring harness joins the main electrical harness and found voltage. This pointed at a fault between that joint and the horn, but it’s one continuous wire and it had good continuity. I then ran a bypass of the old wire from the switch to the horns, which still didn’t work - a check of the voltage at the end of the bypass wire was bad. In depseration, I tried bypassing the switch to the original wiring, and lo and behold, the horns sounded. This confirmed the fault was in the switch, but why ws I still getting a good reading on the probe from the switch’s output terminal? I guessed it must be due to a weak contact which allows insufficient current to operate the horns, so bought a new stalk from the local non-franchised specialist (LR franchises don’t carry Series spares).
Unfortunately, they only had a Britpart stalk in stock, and I wanted the car back on the road quickly, so I took a punt on it. I connected it all up, and initially the headlights wouldn’t work, but this mysteriously rectified itself after cheching the horn functioned correctly. Content that it all looked reasonable well constructed and was now reliably functioning correctly, I set about fitting it to the steering column. I bet you can see where this is going… Yep, Britpart managed to retain their reputation by making the base of the unit the wrong circumference (about 1/4″ too small, as an estimate). Consequently, this stalk will not fit the SIII column, and since SIIs and Defenders have very different stalks, it won’t fit ANY Land Rover! Then again, if you look closely at the slogan on the box, you’ll see they can’t even assemble a sentence properly, nevermind vehicle parts.
The brass blade terminals on the old stalk switch looked a little green inside their clear rubber insulators, but the main connector block looked clean, so I decided it was worth trying replacement of the terminals with new. Thankfully, this worked perfectly - the thin brown horn switch feed must have had a poor contact on the fuse box terminal, but the original stalk is now working perfectly again.
Two annoying, time consuming but zero-cost fixes. At least it’s all working as it should again.
Subscribe by Email
November 24th, 2008 at 7:57 am
You dont seem to be very happy with Britpart. Apart from the stalk you mention, do they sell low quality parts ?
If I make an order to John Craddock or Paddock spares it is very likely that at least 50 % of the items are Britpart labelled.
November 24th, 2008 at 8:37 am
Some of their parts are reputedly OK, but almost everything I have had with their label has either not fit, not worked or not lasted long. Their bearings seem fine, as do many of their electrical parts like starter motors, alternators and lights, but if you ask around on the various LR forums or speak to LR mechanics, you will quickly find that the company are a laughing stock.
The trouble is that many LR owners and non-franchised workshops will buy the cheapest parts rather than the best, so the original manufacturers or superior pattern manufacturers will have to stop their lines while the bad manufacturers corner the market. That means we’ll get into a situation where we won’t have a choice of supplier, and we’ll lose our vehicles because the only available parts don’t work.
Most of Craddock’s stock is Genuine Parts, but the vast majority of Paddocks’ stock is Britpart. I prefer Paddocks’ customer service, and they can often supply Genuine or decently branded parts if you specify it in the order. PA Blanchard and Dunsfold Land Rover are very good sources of Genuine Parts at sensible prices, and have good service and a vast stock.