My harlan RPM switch is not working. After 2 hrs of messing with my set up Now the harlan shows a constant light.

When I try and set the coil per plug or RPM setting.. Nothing.. the light just stays on.

Any suggestions?

I have removed my wire tap and put a splice in it's place to make a better connection.

I will be calling MSD tomorrow to find out if there rpm swicth will work on our cars.

I do not care about cost anymore, I just want it working.

And on the dyno I have, I can guess a good rpm for the setting

Mine still works. =)

Anyways, I didn't just reply to rub it in. When looking for a switch over point make sure you take in to consideration the delay from when the RPM switch sees the correct RPM to the time the actuator recieves vacuum and pulls the butterflies back. I think that could take a few hundred or maybe 1000 RPM at WOT.

I've watched the VI open while my car was dyno'd and yep it is not instant, but it is quick MAX 200 rpm... That was with the harlan working..

I would not know what the time on the MSD is..I would guess about the same

If it turns out your harlan is fried or whatever, Summit makes an adjustable RPM switch to compete with MSD.. I have two of them 45.95$ea , part number SUM-830449

They use dip switches as a Harlan, but there is no # of cylinders to set, its built for 8cyl so you would just divide accordingly for 6. It has a always on switched line, and an always off switched line, like the MSD rpm switch.. so you can use it for nitrous or mevi.

good luck.

Ok, so you lost me on the divde accordingly, how do you set it?

It's tapped into the same line ??( red/wht )

and the always off swicthed line turns on correct

and teh always on switched line turns off correct

sorry if these questions seem dumb , it sounds like a good option , if it does in fact work...

I am wondering if summit just copied harlan or vise versa

"The boxes were a bit more difficult to install than originally expected due to their design; there isn't an adjustment for number of cylinders. The switches are setup to work with 8 cylinder engines from the factory. Even though they specify 4, 6, and 8 cylinder compatibility, there's no way to adjust it. To adapt them to work on a 4 cylinder, you just set them to ½ the desired RPM setting." ~Justin McClanahan

on our car i forget if you act like its a 6cyl or a 1cyl (bc of coil pack) but anyways, hope that makes more sense?

and it has two switched lines, one that cuts the voltage at desired rpm, and one that sends voltage at required rpm. so if you want your nitrous to STOP at 6600rpm, or want your mevi to START at 5300rpm... catch my drift at all?

i dont know who copied what, but its about the some price as harlan, and honestly who would you trust more a big co. or a guy doing it as a hobby? honestly, i dont know haha.. but i havent heard of problems

Thanks for the info

I'll talk to summit and see what they say tomorrow

ok i have come into a new issue with the summit ones. you can adjust from 2000rpm to 9000rpm on a 8cylinder. we are the equivalent of a 1cylinder though (because of tapping an individual coil pack). so, to set our rpm switch at 5300, divide by 8 gives us 662rpm, which is too low to set (minimum 2000rpm on the switch)

anyone have any ideas? I dont know what to do, maybe tap the rpm signal under the dash?

You guys do know that the MSD RPM Switch needs to be send to MSD to be configured for our engines right? Costs about $35.

There is a NEW MSD rpm switch , I think deisgned for the NEW coilless ignitons ( ls6/ls1/2k3 cobra's .. etc).

I have not called summit but I saw it on there website AND my rpm switch is working now but the MEVI is not working.

I should know what it is and solved by friday

The "TAM" screw in back of the dash (also accessible right of the ecu if you know which wire) is certainly possible and would give you a higher divider for your set rpm. Problem is, people have had their Harlans draw too much current and make their tach needle fail. Only happened to me on my 95 when I hooked up two harlans to it. If you already have the Summit switch, you have nothing to lose to try it. If you follow the maximadriver how2, it'll take you about 20 minutes.

any more info on this wire? could i just use the "green" wire on this diagram of the ecu?

Good call on the Summit switch. My Harlan died last weekend too, not sure what the hell happened but my VI no longer works but all the components (aside from the switch) work fine separately. I'll be buying one of those summit switches soon then.

damn... just ordered the Harlan switch the other day too. The MSD one is listed on their website as one of the 2003 new products. According to Summit's site it says they'll have it in stock 7/18/03. I wonder if I can cancel my Harlan switch order now.