Tach and Heater Core Problems

[CJ428CJ]

Hey Bob,

Fired up the Cobra for the first time last night. What a thrill. In any case I encountered two problems:

1. The Stewart Warner tach doesn't function properly. It clearly isn't reading correctly. It's very very slow to respond to changes in engine RPM. What is probably 3000 rpm on the motor reads like 2000 on the gauge and when I shut down, the gauge continues to read about 1500 rpm. I'm running an MSD distrutor and 6AL box. I ran the tach wire directly from the tach connection on the 6AL to the signal connection on the tachometer.

2. After about 15 minutes of running, I noticed my carpet was soaking wet. The heater core seems to be leaking like crazy. I double checked the hose clamps connecting the heater hoses and they're tight with no visible water around the connections. After shutting off the valve at the intake manifold, the dripping slowed way down but small amounts of steam were visible coming through the defroster vents. It seems like there's a bad seam or solder joint in the core itself. Have you had problems with these before?

I'd appreciate any suggestions you might have. Thanks, Bob.

Chris

[Bob Putnam]

Chris,

The tach:

With the engine running, check the voltage at the MSD tach output after disconnecting the wire from the tach. It should be roughly 1.5V.

If that reads closely, try an external tach on the output.

If that's OK, check the back of the SW tach. Doug tells me that some versions have a cylinder selector on the back. Make sure that the the arrow isn't in between numbers.

If all else (doesn't) fail, we'll replace the tach.

Now for the Ugly Part:

This is the first leaking heater that I've heard of. We'll replace it, of course. Give Peter or Bryan a call for details.

[Jim Holden]

CJ:

I remember when I started up my first Cobra the first time...

re the wet floor: did you also check your pants for leaks?

Jim

[Traveller]

HaHaHA!

That was good Jim.

[CJ428CJ]

Man, I'm still laughing. My gf couldn't figure out why I was rolling around on the floor. Then I read it to her and she rolled around with me. Life is good.

Bob, thanks for the feedback. I measured the voltage on the MSD box and I get about 0.5Vdc or 4.0Vac. There doesn't appear to be a cylinder selector switch on the back of mine and unfortunately, I don't have another tach to hook up to the connection. I'll have to see if I can borrow one somewhere.

I'll take the heater core out this week and I'll call Peter about returning it for a replacement.

Chris