308: DASH LIGHTS AND COOLING FANS

I just do the speedo and tach (not all the instruments)...the odd thing is the tach invariably ends up not quite as bright as the speedo. I think it has to do with the substitute bulbs for the tach not being as bright as the replacements for the speedo...but in searching cross referrence charts, that was as good as it gets. Just doing the reostat bypass, seems to make the biggest difference though. The combination of the two makes them much more legible.

 

It's like deja-vu all over again!! I've spent the last year sorting through all this on mine too!

 

I would look at the fan relays as one of the problems. The right fan is on a circuit associated with the AC system and turns on when you turn on the AC. The left fan triggers from the temp. sensor in the bottom of the rad. Also if the AC is off and the water temp triggers the rad. sensor then both fans turn on. So try to jumber out the rad. temp sender to see if the left fan works. Also check the fuse panel sometimes you have a loose connection or rivit which will cause the problem.

 

Michael,
On my '77, both fans come on when the thermostatic switch in the radiator kicks on. But the right fan (passenger side) comes on regardless of operating temperature when the AC is switched on. There is a relay and a fuse for each fan. Both relays are activated by the thermostatic switch. Only the right side fan relay is operated by the AC. But if the thermostatic switch is on AND the AC is on, then the AC turning on the fan is redundant. Anyway. if the thermostatic switch switches on, BOTH fans should work. As you know, the fuseboxes in these cars are almost always responsible for electrical issues, so check that the fuses are supplying current not just to the fans themselves, but also the relays that switch the fans. The relays use a different fuse.

What is the ON temp for that VW thermostatic switch? I would like one that kicks on a little lower in temp.

Birdman

 

I did the rheostat bypass for my dash lights and it worked well, but recently, I picked up a catalogue from an electronic-parts supplier and noticed they sell LED bulbs (with built-in resistor) that looks like they'll fit the gauge lights, on my GT4 at least. Neat thing is they're avaliable in an assortment of colours. LED's offer brilliant, intense light at cool temps, over incandescent bulbs. I'll investigate this further at a later date. Too many winter projects on the go for now.

Below is the before and after pics of my dash with the 'stat bypass. I had posted this in the OLD forum, which seems to be inaccessible now (so I'll repost here):
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Let it idle in the driveway for 10 minutes. The lack of flowing air through the radiator will bring the temps up enough to where the fans should be kicking on.

I just hooked a big battery charger to the battery so it wouldn't die, and turned on the running lights. If you haven't yet done the headlight pop-up mod, the headlights pop up when the running lights are on. Just be careful that they don't go down while you're working on them. You definitely could lose a digit that way.

I agree. The circuit is amazingly simple. The relays get 12 V to their coils from the fusebox. From there, the thermostatic switch in the radiator just closes to ground when the temp hits the right number (180?). It's just a series circuit from the fusebox to the relays (two in parallel) to the thermostatic switch to ground. If the fans work with the switch that the PO installed, he may have (stupidly) disconnected the wire to the thermostatic switch at the back of the relay panel. You can test by just pulling the two wires off the thermostatic switch and check with a voltmeter to see if you have 12 V across those wires. (One is 12 V and the other is ground. I have no idea which is which and it doesn't matter). I'm guessing you won't have 12 V there and if you pull the panel that holds the relays, you will find a lonely wire in there that used to go to the relays from the switch. BTW, you could leave the manual toggle switch AND hook up the thermostatic switch. So you end up with two parallel switches to accomplish the same thing. Sort of like a back up plan system.

It shouldn't. The AC switch operates the right fan only via a completely seperate relay. I'm attaching a simplified schematic of the AC circuit in the car. (It shows only the components that are part of the AC and right fan circuit. It leaves out the other relay for the other fan that is also operated by the thermostatic switch). This schematic shows how the right fan motor (#25 on your OM schematic) can be operated by either relay #99 (via the AC circuit) or relay #30 via the thermostatic switch in the radiator.

I think your problem is in the way the PO modified the circuit for the manual toggle on the radiators. I think he substituted a toggle in the dash for the thermostatic switch in the radiator, probably not realizing that as long as they are in parallel, not series, you can keep both and either one will turn on the fans.

Report back!

Birdman

 

Peter, who is the supplier? I have been wondering why someone hasn't made LED's to replace standard bulbs. How cool would those be as reverse lights, if they could make them bright enough?

 

Mode Electronics

Like I said, I only saw these in the catalogue, not in the flesh, so I don't know if its the same size, but from the description and the picture, they look awfully similar. Model: T3 1/4 (?). Avaliable in bayonet and screw base styles. Again, I have to go back to the store, see if they have them on the shelf and compare to the ones in the car.

If you go to the above link, click on "New Products", you'll see them there and it'll direct you to the page in their catalogue (pg 44 & 45).

 

To keep the lights up simply turn them on and then disonnect the battery. It's a good idea to always do this to work on them anyway so you don't get a finger caught. You won't regret doing the headlights either, I did mine. Pretty easy once I figured out how it all comes apart, and now I can actually see at night!!

On the fan issue mine don't actually come on till about 190 or 195.

 

Wow! I just did the speedo and tach in my 79 308 and didn't even need the jumper wire they are so bright now! I have avoided driving my car at night because of this and the headlight issue, but that has all changed. Thanks to everyone who added to this. Can't wait to do the headlights now...

 

thecarreaper,

I'm not seeing the photos. Did they get lost during the hard drive crash? If so, would you mind reposting them? I'm logged in, so that shouldn't be the problem.

 

Good luck on the headlights...I recommend the Hellas:http://catalog.com/susq/hella/headlamp.htm

Standard bulbs are fine...you could upgrade to the "plus 50%" which are a bit whiter in appearance. The "plus 100%" are a bit blue, I am told.

The Hellas are great on my 328....better performing than the feeble things called headlights on my 355 (and this is called progress?)

 

Cool, Thanks!