Alright, well I'm putting my old Clarion HU into my mums 80's Saab, which as I found out last night, is 24v.. That's right, the Saab is a truck.

How do you guys think I could step down 24VDC to 12VDC? I've looked at some converters but I really think there has to be a cheaper way of doing it.

Thanks.

A nice resistor should help, that's all a step down converter would be... :confused:

I would just get a converter, Jaycar have them.

Jaycar
STOCK-CODE: AA0266 RRP: $26.95

24-12V 3A Converter M038

Many trucks and boats use 24V systems. These converters will allow you to run a reasonably sized 12V car-stereo or other devices from a 24V supply. Heatsink (not included) should be used for superior performance. Features include: short-circuit protection and thermal cut-out. Specifications: Input voltage: 24..26 VDC Output voltage: 12VDC Maximum load: 3A Dimensions: 135 x 50 x 24 mm Heatsink: 50 x 100 x 30 mm (rec. size) use Cat. HH-8572 or similar


Or Better:
STOCK-CODE: MP3068 RRP: $119.95

20Amp 24V to 13.8VDC - Volt Reducer


This switchmode supply will reduce 24VDC to 13.8VDC at loads up to 20A continuous. It features fan cooling, up to 90% efficiency and a very compact design. We would suggest 15A loads in warm climates, or if unit is mounted in such a way that cool air flow is restricted.



Specifications:
* Input Voltage: 20 - 30VDC
* Output Voltage: 12 - 13.8VDC
* Output Current: up to 20Amp Continuous
* Efficiency: 90%
* Dimensions: 120(L) x 73(W) x 73(H)mm
* Weight: 600g
* Short Circuit and Reverse Polarity Protection

A nice resistor should help, that's all a step down converter would be... :confused:

Like I was thinking but I work with a bunch for an electronics company and everyone was saying to go get a converter (less hassle for them I guess).. Jaycar have one for $27 which is 3A, for a HU with the standard MOSFET 50WRMS internal amp wouldn't you draw more than 3 amps?

DAMN you guys are fast.

Like I was thinking but I work with a bunch for an electronics company and everyone was saying to go get a converter (less hassle for them I guess).. Jaycar have one for $27 which is 3A, for a HU with the standard MOSFET 50WRMS internal amp wouldn't you draw more than 3 amps?

DAMN you guys are fast.
Yeah I probably wouldn't go the resistor route, something about an electrical component taking that much abuse without a heatsink would make me a bit nervous. Fork out the $20 :P lol

would 3A hack a HU though? I was thinking more like the $100 option with 20A but really.. I can't say my mum really pumps the tunes so 3A is probably all she'd need, and I'll just wire in a 3A fuseable link so when she cranks the killswitch on the way to work it wont nuke the converter..

3A would be very marginal for a 50WRMS head unit, 3Amps @ 13.8V is 41.4Watts. And they aren't very efficient... Have u checked the HU for a fuse or current rating?

Just look around for a slightly higher power version if you think the 20 Amp version is over kill.

The other problem will be the fact that you need constant 12V for the HU with the possibility of the converter wasting power when the car is off depending on the type of converter, then you'll need a relay or similar setup to switch the 12V ACC power on to the HU when the 24V ACC is turned on.

3A would be very marginal for a 50WRMS head unit, 3Amps @ 13.8V is 41.4Watts. And they aren't very efficient... Have u checked the HU for a fuse or current rating?

Just look around for a slightly higher power version if you think the 20 Amp version is over kill.

The other problem will be the fact that you need constant 12V for the HU with the possibility of the converter wasting power when the car is off depending on the type of converter, then you'll need a relay or similar setup to switch the 12V ACC power on to the HU when the 24V ACC is turned on.

Jeebus, this is what I didn't want to spend time doing. The install is going to be painful enough with out all this crap to go along with it. I guess I'll have to get one of these guys here to write me up something to build that will handle the ACC as well as HU power.

I haven't checked the HU for current or fuse rating, i'll have to get that checked out too I guess.. I don't exactly want to rip my folkes.

Just trying to figure out this loom, I've got a 15A fuse on it also (so atleast I'll get a 10A or 15A converter).

what are my require inputs, It's been a while for me haha

power, earth, ACC (with the acc is it possible to have an acc for switching and then a lights switch also? I can't recall if the unit always had backlighting or if it turned on once i hit the parkers..) I've got 3 wires I can't think of what they're for, won't be aeriel.. ideas?

Alright, well I'm putting my old Clarion HU into my mums 80's Saab, which as I found out last night, is 24v.. That's right, the Saab is a truck.

How do you guys think I could step down 24VDC to 12VDC? I've looked at some converters but I really think there has to be a cheaper way of doing it.

Thanks.

Thats pretty freaky. The engine in those is basically a Triumph Dolomite engine. It was designed for SAAB to replace its two stroke engines that the previous slugs had used (although they called them affectionally, 'toads'). The engine you have is a development of the triumph, which is obvious because they actually work. Dolomites were an abomination, nice looking but represented all of the mechanical defects/inherent unreliabilty that Triumph was famous for. Take the Stag, an exceptionally beautiful car, with a V8 composed of not one, but two dolomite engines put together (1 slant 4 + another slant 4 = v8 :nuts:). Insane, when triumph had a really good v8, the 4.4L that was in the p76 was actually powerfull and reliable.
How SAAB made it reliable is a feat the british could not do. So, after this long ramble, why the hell did SAAB retrofit 24V truck electrics onto this engine? There are a few SAAB experts/victims on here, who know alot more than me :)

Thats pretty freaky. The engine in those is basically a Triumph Dolomite engine. It was designed for SAAB to replace its two stroke engines that the previous slugs had used (although they called them affectionally, 'toads'). The engine you have is a development of the triumph, which is obvious because they actually work. Dolomites were an abomination, nice looking but represented all of the mechanical defects/inherent unreliabilty that Triumph was famous for. Take the Stag, an exceptionally beautiful car, with a V8 composed of not one, but two dolomite engines put together (1 slant 4 + another slant 4 = v8 :nuts:). Insane, when triumph had a really good v8, the 4.4L that was in the p76 was actually powerfull and reliable.
How SAAB made it reliable is a feat the british could not do. So, after this long ramble, why the hell did SAAB retrofit 24V truck electrics onto this engine? There are a few SAAB experts/victims on here, who know alot more than me :)

Yeah everyone i've spoken to is baffled why they would use 24v, so far the only possible idea would be the extra power in cranking the engine when it's minus 300 in all the icey countries Saab are sold in. The engine is also on a 45 degree slant, rather odd, I guess it's for oil drainage reasons, slowing the flow down perhaps..

So far I'm up to rewiring the plug that I tore from the Alpine unit, which was brilliant, it must've been the first of the anti-theft revolution because it has a handle attached to either side of the HU and when you leave the car you simply lift the handle up and slide it out ala computer hard-drive caddies, I just hope it matches your shoes! (weighes about 2kg so you wouldn't wanna be carrying it around in Woolies). Pity i ditched the HU because it most probably had some sort of step-down unit inside it from Alpine, would've been handy.. Also the plug for the HU has 2 power inputs, 3 negatives and 13 other pins which i imagine 8 are for the speakers.. god knows what the others are for..

On another note, how crazy is this kid?!!?

http://en.wikipedia.org/wiki/David_Hahn

The engine is also on a 45 degree slant, rather odd, I guess it's for oil drainage reasons, slowing the flow down perhaps...
Seriously, its because its half a V8. Only british car makers of the 60-70's could do something quite that bizarre

Good luck with the wiring. The jaycar dc-dc converts should do the job with a minimum of fuss. Chuck in a conservative in line fuse, and the worst that can happen is no radio

Just gave Northfield Car Sound a call (They installed my HU for me while I was at work for $60) they quoted me $99 for a 10A "reducer" and $132 for the install or just $132 if I had the required component to step to 12VDC.. That's crazy, I guess I'll be doing it all myself! I just hope this Saab/Alpine HU is the same width as a normal 1DIN unit or then I'll hit another wall!!

Not really...

Standard install for us is $88 24-12v reducer $65
so they have given you a good price.

Youd need at least a 7A reducer ;)

Not really...

Standard install for us is $88 24-12v reducer $65
so they have given you a good price.

Youd need at least a 7A reducer ;)

I managed to get a reducer from work, whilst battling to make one from a regulator and trying to find the right resistors my manager walks up and plops down a regulator that's a complete part for a machine here. Damn, i wish he did that in the morning instead of at the end of the day.

It should be good for 7A but I'm starting it off with 2A fuse, then 5A, I hope that it can survive on a 5A fuse, i guess i'll have to route the fuse to an easy access area haha..