Low Speed Cooling Fans Resistor

[emerydc8]

Does anyone know what kind of resistance the big spring-type dropping resistor behind the left headlight should indicate? I measured mine with a Sears digital volt meter tonight and it's showing .8 ohms. When the fans come on, the current and voltage as measured across the resistor is 4.2 volts and .27 amps. The voltage sounds right but maybe I'm not measuring the current correctly because it sounds really low. Do I measure from the bottom resistor terminal to the top resistor terminal or from the bottom terminal to ground? Or does it even matter? It seems that about every two years I find myself cleaning and repairing the wires and terminals to this resistor. It's amazing how much heat it generates. Do these resistors go out slowly or do they usually work until they completely fail? Thanks!

 

[gsxr]

You can't measure current across a resistor, you must measure current in series. If the resistor is still, well, resisting... it should be ok. Generally they work until they fail.

 

[DarkStar]

I had to rewire my resistor. I think I have replaced 2 of them as well. Not one of the better circuits on the car.

 

[gsxr]

I had to rewire my resistor. I think I have replaced 2 of them as well. Not one of the better circuits on the car.

Agreed. On a side note - don't bypass the resistor. The wiring in that circuit is designed for the reduced current with the resistor in place. If you remove it, current draw goes up, and it will overheat the wiring.

 

[emerydc8]

Thanks. Since it is working well now, I'll leave it alone.

 

[samiam44]

Might want to finish with deoxit and they also make a protectant afterward. Available at many electronics places- Fry's?

Inspect the resistor ceramic for cracks. Make sure you use equivalent gauge wire- I like the silver coated teflon insulated wire. Solderless connectors are available in tinned copper but also brass. I want to say I have an assortment made by Bosch. Very nice compared to H-F , Autozone etc. Next would be the professional grade via Lowes/grainger etc.

Michael

 

[emerydc8]

I did coat it with a Naolox anti-oxidant paste but the resistor gets so hot that I think most of it burned off (at least it smelled like it did). I upgraded to the Lowes solderless terminals a few years ago. Hopefully I'm good for another two years.

 

[Paul64]

I just checked my resistor connections again after a higher than normal temp in town and found them in very poor condition. The upper was almost 'touch and break off' whilst the lower one I could feel cracking as I moved the wire going into the terminal.
I left the engine idling with the bonnet closed (with it open, the visco fan kept the temp to around 95C) to see that the higher speed came in and it did eventually at about 115C... bit too high perhaps but with the low-speed fan running normally, it keeps things under control.
I remade the cable ends about 4 years ago I think so this time, I took out the resistor for a good check over and found the underside of the terminal posts beginning to show signs of overheating too.
I got a new resistor last night (35 Euro) and crimped some heavier cable with more solid connectors into the loom. Hopefully, that's the end of it for a while - the fans get quite a work out here at the moment with daily temps in the mid-30's and high humidity so I thought better safe than sorry.........

Rather sneakily, the new MB part doesn't have the BERU part number, just the manufacturer's stamp (and the fact it was produced in Ireland!). For reference, it's BERU 0110 020 011.

Paul

 

[samiam44]

V=IR,

You know the voltage @ the resistor and the voltage drop accross the resistor. You can calculate the amperage.

Base on my 1-time replacement and wiring at this location. I would replace the resistor when doing the wiring repair or atleast inspect it closely. No cracks in the ceramic of signs of overheating on the back side.

Michael

 

[Jeeze]

I know this is very old, but I have the same resistor with no continuity and I have to replace it. Since all are nla now, what are people using? Anybody know the resistance of this one?
Chris

 

[gsxr]

Chris, last I saw, there were some NOS resistors for sale on eBay. Are those all gone now?

 

[Jeeze]

Chris, last I saw, there were some NOS resistors for sale on eBay. Are those all gone now?

Chris, last I saw, there were some NOS resistors for sale on eBay. Are those all gone now?

I did check eBay..there are some which would take some modification to mount but I don't know the resistance of the original. (.4, .6., ohm )? MB dropped the ball on this circuit.

 

[Jeeze]

I did check eBay..there are some which would take some modification to mount but I don't know the resistance of the original. (.4, .6., ohm )? MB dropped the ball on this circuit.

 

[emerydc8]

Are you sure it's the resistor that is bad or could it be corroded wire terminals or a melted wire leading to the resistor terminal?

 

[gsxr]

Are you sure it's the resistor that is bad or could it be corroded wire terminals or a melted wire leading to the resistor terminal?

Excellent point - make sure it's not the wiring, which is the typical failure. Not often the resistor itself that fails.

 

[gsxr]

I did check eBay..there are some which would take some modification to mount but I don't know the resistance of the original. (.4, .6., ohm )? MB dropped the ball on this circuit.

There are a bunch of used ones on eBay, click here. I don't see any new / NOS at the moment though.

 

[Jeeze]

Here is a pic of it cleaned up. I do have continuity from the one terminal all the way to UNDERNEATH to the second terminal (underneath in the middle of the square block). No continuity to the square plate or the terminal. Will keep trying to get plate off by cleaning up the welded lug on the threads and base

 

[Jeeze]

There are a bunch of used ones on eBay, click here. I don't see any new / NOS at the moment though.

Thank you ! I did a search but did not get those results.

 

[Jeeze]

In conclusion, l bought a used one and installed it and the fans came on right away as soon as the AC kicked in .
Btw, the resistance for this part number is .5 ohms in case you have to use one that is not meant for our cars. Thanks for all the input guys!