Help me diagnose why fuse 9 blows Options

[rosenfe]

On my new to me 74 1.8 . Last week I had a passenger in the front seat. Seat belt light flashing, no start. I had forgotten that belt has to be buckled for it to start. I jumped starter and we got home.At the same tome dash lights and console instruments went dark and alternator light came on. Fuse 9 was blown. What if any relationship between them. Does fuse 9 have some impact on this !

[falcor75]

On my new to me 74 1.8 . Last week I had a passenger in the front seat. Seat belt light flashing, no start. I had forgotten that belt has to be buckled for it to start. I jumped starter and we got home.At the same tome dash lights and console instruments went dark and alternator light came on. Fuse 9 was blown. What if any relationship between them. Does fuse 9 have some impact on this !

It could be a number of things none directly connected to what you have mentioned.
All the instruments powered by it including the center console
Left rear stop and revers lights

Time to arm yourself with a bunch of fuses and methodically try to backtrack the issue.

[Superhawk996]

I'm going to suggest a different approach.

Arm yourself with a Digital Multi-Meter (DMM). Measure resistance to ground on both sides of the fuse block.

Fuses blow for a reason - by doing so they protect the wiring.

Don't just start plugging fuses back in and waiting for them to blow. By doing that you are repeatedly exposing the wiring to an overcurrent condition. (IMG:style_emoticons/default/sad.gif) It's a good way to melt wiring while you troubleshoot.

A DMM allows you to troubleshoot it without flowing high current.

If you don't already have a DMM - go buy one. If you don't know how to use one, get on Google and spend some time with a 9V battery and some spare wire.

A DMM will be one of the best tool investments you ever made. Can test batteries, test household wiring, capacitors, relays, diodes, etc. You'll wonder how you ever lived without one.

And equally as importantly, use a wiring schematic. Again, if you don't know how to read one, now is the time to learn.

Randomly chasing things around trial and error without a DMM and a schematic is a waste of time.

[Puebloswatcop]

Fuse 9 does in fact have a direct corelation to the seatbelt system, both at the seatbelt warning light and the seatbelt warning system relay. The other feed it has are the brake switch and reverse switch, so check to be sure your reverse and stop switches or lights arent creating an issue.

I would suspect that if the problem never occurred until someone sat in the passenger seat, the problem may well be somewhere in that circuit. (IMG:style_emoticons/default/headbang.gif)

[DC_neun_vierzehn]

I'm going to suggest a different approach.

Arm yourself with a Digital Multi-Meter (DMM). Measure resistance to ground on both sides of the fuse block.

Fuses blow for a reason - by doing so they protect the wiring.

Don't just start plugging fuses back in and waiting for them to blow. By doing that you are repeatedly exposing the wiring to an overcurrent condition. (IMG:style_emoticons/default/sad.gif) It's a good way to melt wiring while you troubleshoot.

A DMM allows you to troubleshoot it without flowing high current.

If you don't already have a DMM - go buy one. If you don't know how to use one, get on Google and spend some time with a 9V battery and some spare wire.

A DMM will be one of the best tool investments you ever made. Can test batteries, test household wiring, capacitors, relays, diodes, etc. You'll wonder how you ever lived without one.

And equally as importantly, use a wiring schematic. Again, if you don't know how to read one, now is the time to learn.

Randomly chasing things around trial and error without a DMM and a schematic is a waste of time.

Can you recommend a good DMM?

[wonkipop]

Fuse 9 does in fact have a direct corelation to the seatbelt system, both at the seatbelt warning light and the seatbelt warning system relay. The other feed it has are the brake switch and reverse switch, so check to be sure your reverse and stop switches or lights arent creating an issue.

I would suspect that if the problem never occurred until someone sat in the passenger seat, the problem may well be somewhere in that circuit. (IMG:style_emoticons/default/headbang.gif)

yep.

been there done that 30 years ago.
multiple head injuries on brick wall moment.

[dhuckabay]

For what you are doing any cheap one will work to measure ohms. Harbor Freight has one under $10. No reason to buy an expensive Fluke for this.

I'm going to suggest a different approach.

Arm yourself with a Digital Multi-Meter (DMM). Measure resistance to ground on both sides of the fuse block.

Fuses blow for a reason - by doing so they protect the wiring.

Don't just start plugging fuses back in and waiting for them to blow. By doing that you are repeatedly exposing the wiring to an overcurrent condition. (IMG:style_emoticons/default/sad.gif) It's a good way to melt wiring while you troubleshoot.

A DMM allows you to troubleshoot it without flowing high current.

If you don't already have a DMM - go buy one. If you don't know how to use one, get on Google and spend some time with a 9V battery and some spare wire.

A DMM will be one of the best tool investments you ever made. Can test batteries, test household wiring, capacitors, relays, diodes, etc. You'll wonder how you ever lived without one.

And equally as importantly, use a wiring schematic. Again, if you don't know how to read one, now is the time to learn.

Randomly chasing things around trial and error without a DMM and a schematic is a waste of time.

Can you recommend a good DMM?

[76-914]

An auto ranging Fluke is pricey but they are worth it over time. I've had mine for 30+ years. However if you won't be using it much get the Harbor Freight unit. Get one that measures Amps as well. (IMG:style_emoticons/default/beerchug.gif)

[jrmdir]

If, like me, you live closer to a Lowes than HF, they have a Kobalt brand meter for $20. Looks a bit more durable than the HF one. Would imagine Home Depot has similar.

https://www.lowes.com/pd/Kobalt-Mini-Multimeter/5001927061

Ron

[Superhawk996]

Fluke is the gold standard but indeed they are pricey.

I've had great luck with HF higher end DMM's. Latest is AMES DM1010. Very happy with it. $95 or so.

https://www.harborfreight.com/dm1010-profes...eter-64021.html

I also have a couple of the Cen Tech 14 in 1 units like this for over 5 years.
https://www.harborfreight.com/5-in-1-digita...eter-98674.html

They are OK but sometimes the resistance mesurement locks up if switching the selector switch too quickly. Its a quirk but not a fatal flaw. Not bad for units that I toss around in cars and consisder semi-expendable.

These are about $79 but I think they are no longer making them and just selling out existing inventory or so it would seem in my local store.

Both are capable of measurement of 10A current (and fused) which is a key feature for me. There are times you may want to monitor Ignition off Current Draw - can't do that without a current measurement mode.

[jrmdir]

Rosenfe: Back to your episode description - what do you mean by "I jumped the starter"?

What specifically did you do? The sequence of events might help narrow the search.

Ron

[rosenfe]

Finally took to local Indy. Turn signal bad. All good now