Just put in a DH fusebox upgrade, ran with no problems for about 30miles. The car ran hot today, checked the fans and the left side was not running. Checked the fusebox and the left fan fuse had popped. Plugged in another one and I heard it pop just when I started to crank the engine over. Hooked up straight power to the left fan and it ran no problem. Any thoughts.
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What was the fuse A rating that was popping? It might be a lower one than what is required by the original spec. Sent from my iPhone using Tapatalk
Correct 20amp fuse installed. Hooked up direct 12v to left fan and it runs no problem there. Only thing I changed was the fusebox upgrade. All wires connected correctly. So did I'm swaying on something happened during the upgrade.
Since you report that a new fuse blew immediately during cranking, I'd unplug the harness at the LH motor and see if a fresh fuses still blows immediately when cranking/running. If it does = serious problem, but can't be the motor. If it doesn't: This really isn't a 100% guarantee that everything is OK with the LH motor. What you'd need to know is what is the current when the fan is running with the +12V applied: If the current is reasonable, say ~10A, but the fuse blows, I'd make sure that the prongs on the fuse-relay panel holding the fuse terminals ends are tight and clean. A poor connection there can add extra heating into the fuse so it "blows" (melts) at a lower than rated current (although this scenario doesn't really agree with "blows immediately while cranking"). If the current is unreasonable, say ~15A, then there's probably some excessive drag in the motor (which reduces the RPM and back EMF so the current goes up for the same applied voltage). One good thing about TR systems is that there are usually two of everything so you could do things like compare the current in the LH motor vs the RH motor, or just spin each fan by hand (when not powered electrically) to see if the drag is way different or not. Try some of that and give a shout back...
I wonder why the fuse blows during starting? even the ignition is off there will be always power on the fuse because the fans running also after engine is stopped controlled only by the thermoswitch. so that the fuse blows is for me a sign, that there is to this fuse connected something other also, may be an alarm? but as steve mentioned, may be somewhere loose connection? then new fuse you used has the same amp? not that you put one in with lower amp
Steve, I plugged in a 25amp fuse and tested the amp draw of the fan (which is new) and at startup it hit 21-23amps a few times but most of the time it was like 17amps settling to about 11-12amps while running. The two 20amp fuses that blew were the glow type fuses that came with the upgrade. When I put in reg 20amp fuse it hasn't blown after about 10 startups. Was it the glow type fuse maybe not truely rated 20amps. The fuse in the terminal are a firm fit but not tight, I can wiggle the fuse a bit, which I have a concern, especially if it could cause more of a draw. I hooked my old fan back up and it read about the same amp draw at startup and while running. The amp draw on other fan (also new) was 21amps a few times but most of time it was 17amps at startup settling to 11amps running and that glow fuse hasn't blown yet. Tomorrow I'm gonna swap another 20amp glow fuse onto this fan and see if it blows.
I had a similar problem with the right fan when I first got my 89 TR. my cure was removing a small amount of corrosion on the fan plug itself. I used a standard 20amp fuse not the glow type. It hasn't blow a fuse in 8 years since I cleaned the connector. Britt
When I first did the DH fusebox upgrade the same thing happened. I think it was a 20A fuse, and only one side kept on popping. Looking at the manual, it calls for a 25A fuse. While I did talk to Dave about it - and we went back and forth about how the fan shouldn't be drawing that much - I left it in with the 25A fuse and never had an issue since. At the last major - I swapped out both fans since the engine was out. Now you have me curious if it will run on the 20A fuse.
That sounds sort of normal-ish, and shows the conundrum of needing a motor fuse big enough (and slow enough) to not blow at motor start-up, but such a big fuse not really giving any steady-state protection like Dave mentioned. Fuses can have different current-to-blow versus time-to-blow behavior so the glow fuse SRI substituted may be a little different in this respect (and, if a lower-current rated fuse than stock fuse, that will also move in the direction of having less margin for start-up). One can almost say that the fuse really only protects against having a direct short somewhere (i.e., a very high current situation) as, if the steady-state current was 20A, a 25A wouldn't blow, but the wiring would probably melt . When you say you installed "new motors", does that mean you installed new stock motors, an equivalent motor, or an uprated motor? Even if stock, new ball bearing brush electric motors tend to be a little "tighter" than a well-working already-run-in motor (i.e., new ones have slightly more drag so start a little slower and have a higher start-up current for a longer time). The usual situation for the SRI upgrade install is fixing just frazzled white connectors so they go into TR with already well run-in water radiator fan motors = so would see a less stressful situation for the fuses at start-up than you have (and might be a situation that SRI has rarely encountered). Just a thought...
I don't have the SRI fuse-relay panel modification -- I made my own modifications to add high-current capable wiring paths (in parallel to the troublesome white connector connections) directly from the stock relays' conveniently extra 87 output terminal to the output wires leaving the white connectors (and other modifications, too, to the brake light and starter solenoid wiring paths). Haven't had any trouble with my oil fan operation (yet ) so haven't messed with that one.
