MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Fuse Keeps Blowing

I Hope Dan M see's this thread! I keep popping my fuse on the green circuit and losing brake lights, turn signal and a couple of gauges. Since it only occurs sporadically it is not a constant load issue but probably a contact getting out of hand when i hit a bump in the road? I am suspicious of the heater being the suspect since it doesn't operate regardless of the fuse being operable but was wondering what is the best way to chase down why a fuse pops. Dan, I read your book cover to cover but still am at a loss and am not an electrician by any stretch of the imagination. Any suggestions out there?

Thanks

bob

Bob Craske

Hi Bob,
It sounds like the problem goes away if your able to put in a new fuse and it goes again later...it might be a bare live connection going to ground but it could also be that maybe the fuse is the wrong value for that circuit and when the load exceeds its rating it blows. As I recall the heater,wipers,turn signals and fuel and temp gauges are all on that line.
It might be a process of elimination of each circuit if the problem stays... it will be easier to find with an ohm meter.
Charlie
Charlie Ballard

Charlie...thats 100 correct...

Using Dans book, I made sure that I had a correct fuse in that circuit (I used a 25 LUCAS before that popped so inserted a 35 LUCAS which I understand to be 20A effective)

now the embarrasing part...I dont know how to use an ohm meter even though I own one! I just hate the thought of tearing apart the trunk and the dash to find this problematic wire and was hoping for some experienced guidance on how to avoid making a mess of things!

if you have an article you can pint me to I might try to figure it out this weekend. Of course, one wont know if i fixed the problem until I drive over some potholes?

thanks

bob
Bob Craske

Bob,

That's probably one of the most difficult kinds of problems to solve! The green fuse feeds the heater, turn signals, seat belt warning system (if you have a later model), WS wipers, WS washer, overdrive (if equipped), brake lights, reverse lights, and the two gauges - fuel and temp.

You have two options for finding the fault - do a "hand-over-hand" inspection of all the green wires in the car, looking for a fault, or by the process of elimination, find the fault. Given that the problem is intermittant, using an ohmeter won't help unless you get lucky. Most of the time, you have no problem, and the ohmmeter won't show anything until you do.

I'd try the modified version of the hand-over-hand method first, looking for the obvious without tearing anything out of the car. If that doesn't turn up anything, then do the process of elimination.

If I understand your problem, it only occurs when you are driving, and then probably only when you hit a bump or do a quick maneuver. You have no option but to have your gauges working and to use the brake lights, but try to drive without using any of the other loads and use your brakes as sparingly as you can. If the fuse blows, then you know the problem is in one of these two circuits, or it's in the main green wire circuit before the green wires get to any of the switches.

The next step is to pull the green wire off either the brake switch or the gauges, and try again. If it still blows, replace whichever wire you pulled and pull the other one and try again. If it still blows, the problem is in the green wires before any switch, and you'll then have no choice but to do the hand-over-hand ispection.

If the fuse doesn't blow, operate one of the other loads at a time until you find the load that blows the fuse. Then, you'll need to do an inspection of that circuit to find the problem.

To make the process easier, you may want to wire a test lamp to the green fuse (on the green wire side), and have the lamp in the car where you can see it. This way, you'll know exactly when the fuse blows, and you can compare the time it blows to whatever you were doing at the time.

Good luck!
Dan Masters

Bob
(Dan, Bobs' 6 is 1976, so as you know, seat belt junk not involved in this circuit for this year).
Bob, do not put in a larger fuse to try and stop the problem...you will only heat the wires up and posibble do more harm.
Dan said it all...gotta agree..chasing down an intermitent with an ohm meter is...well.....forget it! Unfortunatley, this circuit controls a lot and is mostly at the most inconvenient location up under the dash!
Bob keep in mind when Dan says "hand-over-hand inspection" , he is meaning you are looking for a "bared" wire...the insulation has come off or has been rubbed off and is intermitently touching metal.
This will ALWAYS be the power side to whatever the wire supplies power to and will always be the green wire (with 3 exceptions).
NOTE: The first thing I suggest you do is disconnect the heater wires (and tape them) from the heater completely since you might have a short in it..you said it is not working.

Might I suggest you look at the 3 exceptions first. They are the brake, reverse, and rear turn(only) lights. They are the only 3 critters that go to the back of the car. They exit the main harness at a MOLEX connector located behind the driver left kick pannel and travel down the outside drivers floor pan under the carpet. This harness can be "pulled/shaken/ twisted (but not stired:) with something in the circuit on to see if the fuse blows. Also have a look at the brake light switch itself..has been know to fail. Take a good look at the harness as it travels the drivers floor pan. The wires are GREEN with another colour tracer (see schematics for colours). The R turn travels between the outer and inner body panels at the very back of the car ...you will not be able to get at the wire going to the R turn. You can, however, "wiggle" it with turn signal on and see if the fuse blows.
The only other thing in this circuit is the "bulb test relay". I am unfamiliar with this. Dan..comments??

Bob, I can only say good luck...one of the most frustrating situations in electronics.

Rick C
Rick Crawford

Bob,

Had a similar problem some months ago. Found that the conectors on the fuse box was the issue, just getting old like a lot of us. I moved the connections to the spare connectors on the fuse box, and haven't had a problem since.

Hope this helps and you can try it in a matter if seconds.

Joe
J. Caruana

Bob,

I had the exact same problem last year on my '71 TR6. It went on for a couple of months. Let me ask you a question - do your windshield wipers work? Mine do not. I unplugged my wiper motor last December and I haven't had the problem since.

There's (I think) four wires that go into a plug which is connected to the motor. Disconnect the plug, drive the car around (assuming it's not raining), and let us know if this fixes it.

Prior to unplugging the motor, I did what most have suggested above by trying to pin down what was causing the problem. Someone finally mentioned to me on another forum to check the wiper motor for shorts. They had the same problem you and I had before with a TR6 and the wiper motor was the issue.

I haven't pulled my motor to look at it yet, but I've heard they're pretty easy to remove, clean-up, repair, and replace. Right now I just drive when the sun is out because I don't have a top on my car anyway.

I hope this helps.

Cain

Cain

Well, followed all the advice posted and guess what...its the heater that pops the fuse every time I turn it on. so I can choose not to use or I can get finiky and figure out a repair...since I am somewhat anal about this restoration I thought I d try to repair..(no snickering Mr Horne!)

So seeking more advice...

I do not want to remove the glovebox and dash, so i thought I d see what is the best test to apply to the heater while still in the car....then I can post the results of the tests suggested and plan the next course of action

thanks for all the help

bob
Bob Craske

It sounds like the heater motor bearings are dry and dirty. Some disassembly required, AFAIK.
Tom

Bob
You got lucky and found the problem fast...well maybe not all that lucky since it is the heater motor;). Yes it could be the bearings and it could also be the windings in the motor.
TEST: Take 2 heavy gauge wires (14AWG) directly from fuse and -terminal of Bat. to the heater. Disconnect the "out" side of the fuse and just have the wire going to the heater. Touch wire to heater wire (ya you will get a little spark) and listen how the motor "winds up"...it may just pop the fuse though. If fuse pops immediately...well...sorry. If motor labours and then pops fuse...well...sorry. If ok then read bottom of my post.
Just a thought...maybe there is an obstruction in there (birds nest) that is preventing fan from turning,this will pop a fuse. Man! de ja vu on that last statement...seems there was a post long ago on this.
Unfortunately there is no real easy way of getting at the fan to try and turn it by hand/finger.
You have not got an easy one Bob. But you do have all winter:) Ya I know..thanks Rick.

Question? your first post you say fuse pops as you go over a bump? Was the heater on or off? You now say fuse pops as you turn the heater on ...I presume as you are sitting stationary. Take a close look at the wiring going to the heater. Also a close look at the heater pull switch. There is a lot of metal around the switch so look at wire fraying.
Have you always had this problem or just recently?

As you can see, several things to look at before the motor comes out.
Good luck and keep us posted.
Rick C

Rick Crawford

You don't *have* to pull the dash to remove the heater, but one pesky nut is best reached through the ashtray! I figure about 4 hours to pull the heater and another 4 to replace it if you're starting from scratch. Seats, transmission cover, glovebox, etc.

Some people contend it's quicker to pull the dash, but either way, do everything to the heater (hoses & such) that you envision doing because once is enough! It is a good opportunity to clean up the wiring, though.

I posted on this about 18 months ago.
EC Smith

Well...thanks to Dan M's book, a contorted spine and some real dumb a** luck, the problem is solved...to anyone out there with a similar problem...recheck the order of the wiring to the actual switch...i must have been dyslexic when wiring because I had GREEN and GREEN/YELLOW reversed in switch position...repositioned, and voila, no blown fuse and lots of blower air...

Thanks all

Bob Craske

Bob,

I guess you are talking about the heater switch?

Thanks,

Cain
Cain

Unplugging the heater fan fixed my similar problem! Fortunately, we don't get any cold weather in South Florida!

John
JL Bryan

Cain

Yup, this was for the heater switch...


bob
Bob Craske

Hi, I have a 1980 triumph tr7. The problem is the wiper motor will not shut off. I reground the wiper motor wire directly to the neg. battery terminal. This did not work. Is there a limit switch or relay that won't allow the break?
Vince

Vince,

Sounds like your park switch is stuck. It sometimes does get stuck when the greae inside the housing gets old and hard. See the link below for more info on this.

http://www.vtr.org/maintain/wiper-motor/
Dan Masters

This thread was discussed between 27/10/2004 and 22/12/2004

Triumph TR6 index