? 1989 Testarossa

I have a 7.5 Amp fuse that keeps blowing out that controls controls my panel lights and tail lights. I found a short in the rear deck piston and replaced that but the fuse still blows ocasionally. It is an Intermittent problem. Any help will be greatly appreciated.
Thanks,
Bobby

 

Can you be more specific about the fuse number per the (US) OM figure on page 97? Is it #13? Alternatively, to detemine the fuse number, just count over starting with fuse #1 being on the RHD side.

I'll be glad to cast an eyeball over the TR wiring diagram to see what gizmos would be involved and if there might be a way to narrow things down.

(If it's not a US version please let me know that too.)

 

Thank you so much for your response. I believe you are correct. It is fuse #13. I double checked on page 97. This is a US version.
Bobby

 

Bobby -- I replaced fuse #13 on my US TR with an ammeter, and, at warm idle with the exterior lights "on", I measured the current draw at 4.75A (which seems reasonable for a circuit protected by a 7.5A fuse).

The items served by that #13 fuse are (many):
items 1 -- front running lights
items 7 -- side (front) running lights
items 138 -- rear running lights
items 132 -- side (rear) running lights
item 15 -- front bonnet light
items 74 -- ashtray lights
item 3 -- dimmer for instrument lights
item 39 -- "P" (parking) warning light on the left side of the dash
item 48 -- the indicator lamp in the dash for "lights on" indication
item 102 -- light for tape recorder box (a truly horrible translation -- I believe this is the light inside the compartment with the hinged lid at the back of the central tunnel)
items 122 -- engine compartment lights
items 133 -- license plate lights
item 88 -- lamp inside rear window heater switch
item 89 -- lamp inside fog light switch
items 100 -- Light for tunnel luggage (another mis-translation I believe -- I think these are the lamps along the interior sides of the central tunnel to illuminate the field of switches)

If the current flowing thru your fuse #13 position (when it works) is much higher than mine -- I'd guess that someone replaced some of the bulbs with the wrong wattage or has added something to that circuit (alarm?) that is drawing more current.

If the current is about the same (when it works), but the fuse still blows occassionally -- the things I'd check first are:

1. Ensure the wires going to the license plate lights are not melting/shorting to the (hot) exhaust system;

2. Check to see if someone has removed the ashtray lamps -- perhaps if the bulbs are missing completely, the hot wire could come in contact with the grounded socket (I've been thinking about disabling mine);

3. IIRC, the lamp holder and pushbutton switch contacts for that "light for tape recorder box" are very exposed -- make sure they're not contacting something grounded flopping around inside the central tunnel.

Just some suggestions. Good luck with the hunt -- give a shout if needed.

 

Steve, that is more info than I ever expected. Thanks for all the hints. I will check out all of your suggestions and I will let you know what he comes up with.

I have been trying to narrow it down to when the fuse blows. I have run the car for 2 days now with no failure but the last time it blew I had just run over some railroad tracks, yes very slowly but something may be shorting out when I experiece rough roads.

Thanks again. I will let you know what I find. Have you had the same problem?
Bobby

 

Well, let's hope it's more information than you actually need

Glad to help out if/when I can -- especially my TR brethren. I haven't had your exact type of problem, but I've chased enough other Gremlins around my TR that I'm fairly familiar with the TR's electrical system. In the past I've said in jest that the TR toolkit should've included a multimeter, but it's really no joke -- it would be a miracle to own/use a TR for ~5 years and not have some sort of electrical issue to address IME.

Let us know how it works out.

 

the dash lights and rear numberplate lights fuse kept blowing on mine every time i turned the lights on so i put in a bigger fuse and its been ok for 2 months now not sure what size fuse was but if it was a 10 amp i put in a 20 amp

 

I am sure at some higher amperage the fuse would stop blowing but make sure your fire extinguisher is handy.

I remember the old house fuses that would screw in. If they kept blowing you would put a penny in first. This always worked until your house burned down.

Be careful,
Boca Bab

 

I have not looked at my diagrams but if it is the same circut as the engine comp or brake lights the electrified gas struts on some cars due to production tolerances will short from the body of the strut to the engine cover. It happens intermittantly due to body flexing. It is a problem Ferrari was aware about from very early in the cars production life.

Very close examination may reveal the problem spot.

Ferrari advised us to sleeve the gas strut with heat shrink tubing. It works quite well and if done in a tidy fashion is almost invisable.

 

Thanks great idea. That is exactly where we first found the problem so I replaced one of the struts. Still blew after that. I will try your idea.
Bob