vettepoor

I need help with ballast resistor ohm readings. Old resistor read 1.9 ohms and I was told I needed a .8 ohm resistor for my MSD Blaster 2 coil. Went to NAPA and picked up Echlin resistor #1CR5500 which is supposed to be rated at .85 ohms. I get a reading of 5.5 on my meter. What gives?

AZDoug

I am going to throw out a guess that the Echlin number 5500 means 5.5 ohms,and you were given the wrong resistor.

Doug

patriotpa

http://www.napaonline.com/Catalog/Ca...500_0006342489

vettepoor

Doug- That was my thought as well. They brought it up on their screen while I was there and it did in fact show .85 ohms! I can't find any info on line to confirm this however.

John

65tripleblack

Ballast resistors are designed to get hot..........that's why they are encased in ceramic. Resistance increases with temperature.

Ballast resistors' rated resistance is measured at a specific temperature.

vettepoor

OK, but that means that at operating temps the resistance would increase above the already too high 5.5 ohm reading, true? I am confused!

65GGvert

The ballast is wire wound internally, the ceramic disperses the heat. The resistance will change very little (almost zero change) at any temperature. You should measure .8 ohms if your meter is correct and your leads are making good contact so as not to create resistance. A reading of 5.5 ohms on a .8 ohm resistor is not correct. If your other resistor measures correctly with your ohmmeter, the new resistor is not correct.

65GGvert

The statement you refer to was incorrect.

vettepoor

I can only assume at this point that old ballast resistor reading was correct, or my meter is wrong. I'll check back with Napa to try to confirm what's right. This should be fun......

65GGvert

Check your ohmmeter by shorting the two leads together and see how close to zero you get, remeasure the resistor and post back what you find.

vettepoor

I get a reading of .2 on meter with leads shorted out. I know it should zero out, but doesn't at lowest setting of 200 ohms. Resistor reads 5.5 which I guess should be 5.3 corrected. Just returned from Napa, they gave me copy of spec sheet on echlin part, shows .85 ohm rating. I am calling echlin help line tomorrow - either got miss packed or they know something I don't. Stay tuned.

patriotpa

You're just measuring the resistance of your leads. Subtract 0.2 ohms from your reading and you'll be good to go.

65GGvert

I can't imagine why any ballast resistor would be 5.5 ohms. You would get very little voltage drop at the coil and almost all at the resistor. I don't think the car would even run. Let's see what they say.

Powershift

Why not just buy this one. It is the one MSD recommends for your coil.

http://www.autozone.com/batteries-st...sistor/139539/

http://www.summitracing.com/parts/ms...FZWCaQod-lUAjQ

I got this info by going on-line and Googling "MSD ballast resistor"

Larry

vettepoor

I may do just that, depending on how this shakes out. Just trying to find one locally.

Powershift

No AutoZones in Hawaii??

Larry

vettepoor

Nope, not here on Maui anyway. Napa is "go-to" source for most of us. Have O'Reillys here, never have had much luck there.

After38Years

Maui NO KA 'OI, but Napa maybe not....

Frankie the Fink

I'm really trying to be sympathetic with your situation on Maui
Its not working out though

vettepoor

Those of you who have followed this thread, I took my multimeter with me and returned ballast resistor. Napa had another in stock, so we checked it - also read 5.5 ohms! I called echlin help line from store and guy told me they must have mis-packaged these. Ya think? He said to try a different part #, told me it was supposed to be .8 ohm unit I was after. Well, not in stock, plus computer showed new part to be 5 ohm, not .8!! So much for quality control - I guess I'll order on line and pray.