Help! 308's new thermoswitch stopped working

If you turn the lil' box over and look it says.."Made in (Fill in the blank)"....

You'd better go get another one...........

 

"If it wasn't for low quality, there would be none"

Buy another, hope for the best.

 

This is a recurrent problem with many older cars, especially if you replace these with "old" style switches. In the old Jaguars, they used a thermo switch called an "Otter" switch, called that for the company that made them. They contain a bi-metal mechanism that is notorious for failing, especially when most needed on a hot day (proof of Murphy's law and several corolaries). That was the case until some folks figured out that in some of the radiators, a VW solid state thermoswitch would fit and work just fine. Now, I haven't looked into the issue, but I wouldn't be surprised if you could get an appropriate temperature range solid state switch used in another car that would fit our 308s. The solid state switches are far less prone to failure than the bi-metal type. OTOH, you may just have gotten a bad switch. Either way, the only way to fix it is to replace it.

 

Oh, one other thing, IIRC, the 308 switch is at the top of the radiator. If so, I've seen situations on other cars where the water level in the radiator drops and the switch is not being heated by a steady flow of coolant. Be sure that you don't have air in the top of your radiator that is keeping the switch from contacting the coolant. If the radiator is full, then it's the switch.

 

Yup. That's what I have, and the switch itself is actually not the problem. Mine connects directly to the high amp fan which burns them out either in a couple of weeks up to a couple of years. One needs to put a relay in the circuit which solves this problem. If Ferrari did the same thing, you might consider installing a relay too; check your wiring.

Ken

 

Ken, you're correct. The Jaguar systems did have relays (they were probably ahead of their time on that one), but they were Lucas relays and prone to failure as well. On XKEs, I ended up installing the solid state Otter with a Bosch relay and henceforth no more fan problems.

 

I would check the resistance of your fan motors. If a motor is failing and drawing excessive current the switch could fail quite rapidly. A partially seized motor could be the culprit.

Mark

 

The thermoswitch is isolated from the fan motor current by relays in this case, but your point still applies (and closing 2 relays is a bigger strain on the thrermoswitch than on cars with just one relay). Measure the current flowing in the closed (warm) thermoswitch -- shouldn't be more than 0.35~0.5A IIRC for two ...113 relays. If it's something like more than 1 amp that would indicate trouble, but you might check what the thermoswitch rated current is if you've made a substitution.

 

Steve,
Old Age is approaching because your memory is failing....the switch is at the bottom of the radiator!

Birdman

 

I know the "two pole" (has to electrical male spade connectors) that fits the VW Rabbit from 75-82 (early eighties) works. Make sure you get a new gasket too. This also fits Audis and Porsche 924's of the same vintage.

 

Not sure if you meant the electrical resistance of the motor or the physical resistance of turning it by hand via the fan blades. Certainly turning it by hand and comparing the physical resistance compared to a known good motor/fan could give you an idea. If you want to check it electrically you need to make a current measurement, while it's running, with an ammeter and compare the reading with a known good motor. The current draw should be close to identical.

In any case, if there is no relay between the fan motors and the thermo switch you really must install one (two actually). Same with horns, headlights, electric windows and other high current draw items on any car that does not have them.

Erich

 

Sept. 2022 Update:
The only supplier of replacement switches that I am able to find is NAPA. I searched for '77 VW Rabbit switch and only the NAPA Echlin FA252 is currently available. Replaced it today and it works like it's supposed to. How long?? Who knows??
https://www.napaonline.com/en/p/ECHFS252

 

I just did a google search and many options come up for VW/Audi fan switches.
Just remember you need a two pole.
Here is a vendor selling the Neuspeed 180F switch for $19.
https://www.urotuning.com/products/neuspeed-fan-switch-2-pole-fox-jetta-rabbit-gti-rabbit-scirocco?currency=USD&variant=41306462355649&utm_medium=cpc&utm_source=google&utm_campaign=Google%20Shopping&gclid=CjwKCAjwm8WZBhBUEiwA178UnNvdCgHyXaKuqFZyorAzRpX3dWv_qM5QJQfnwAvfiPkmqj77k12VbhoC-RcQAvD_BwE

You could also go to a VW or Audi dealer as well.