dayoff53

Hey, guys! I'm new on this forum - was referred here by some buddies at toyotamotorhome.org/forums. I have a '92 Winnebago Warrior WT321RL (I know - who cares?) built on a '91 'yota 3.0 V6 1-ton dually cab and chassis, which is basically a '91 pickup with some beefing up. It came with the standard instrument cluster, which I have recently swapped out, after reading several threads here.
The problem I had is that I couldn't use a 4Runner cluster because I needed the gear indicator lights in the instrument cluster and the 4Runner had them in a separate panel. Soooo... I found an instrument cluster from a '95 (maybe '94, but the part was made 9/94, so I think that has to be in a '95 rig) T100 V6. Luckily it had the mechanical speedo, so that part of the swap was easy. And I got the oil pressure sender from the same truck and swapped that - had to remodel the electrical connection a bit. I set the odometer to the correct mileage - had to take apart some things that aren't supposed to come apart, but my machinist brother helped with that, then it took some playing to figure out how the wheels worked, but I set it to the next whole mile above what the old one was (no tenths on the new one). So, everything should be good - but not so. I have 2 problems.
1) the tach is erratic as all get out. The tach wire was already in place, but the tach needle jumps up and down a LOT, to the point that it is really useless. We tried adjusting the potentiometer, using a diagnostic tach for reference, but got nowhere. We did notice that this instrument cluster has a separate PC board added on the back for the tach and a similar one we put in my brother's similar motorhome did not. Could that have something to do with it? Anybody know a fix?
2) the temperature gauge is rock steady and dead center - ALWAYS. That may be reassuring, but it is WRONG. Going ob a long, steep hill at 95 degrees F with the engine roaring in 2nd gear, no change in temperature. I know how the temperature gauge appeared in the old cluster - generally pretty steady at about 1/3, but going up above middle on the long uphill pulls - and the "new" one is clearly not reading correctly. My brother's similar swap has the same issue regarding the temperature readings. Do we need to swap some other part - like a thermometer or related sending unit?
3) oh, yeah! One other thing while I am thinking about it. The new cluster doesn't have a light indicating that the the ECT (electronically controlled transmission) is in the "Power" mode - is that just a missing bulb, or does it not have that function?

Thank you for any help you can give. This forum is a great resource for the fans of the old Toyota motorhomes!

dayoff53

Well, I got the tach problem fixed. If others have similar problems, here's what I found out: When we used a diagnostic tach (plugged in to the spade connector designed for that purpose right next to the fuse box under the hood), the tach in the instrument cluster worked fine. Using the screw on the potentiometer, we could get it adjusted correctly. Then, we would put the dash back together... and the tach would be way off and jumping around all over the place. We tried removing the small add-on printed circuit board (rectangular with 3 leads coming from it and attached to the main circuit board for the instrument cluster), but the results were the same.
Finally, we realized that unplugging the diagnostic tach is what caused it to go haywire, so we scratched our heads and tried to figure out why. Finally, we checked what the diagnostic tach was doing electrically and found that there was about 1434 ohms of resistance between the pulse lead and the negative terminal of the battery. We then checked the add-on pc board and found the same 1434 ohms or resistance between the black wire and the light colored wire. Sooo.... we put that little pc board back on the instrument cluster but connected only those 2 wires, attaching the black wire to its original terminal, but attaching the light colored wire to the "P" (for pulse) terminal. Ta Da! It worked like a charm! The tach is now very steady and reads correctly at all RPMs.
As to the temperature gauge, it is clearly working. It apparently just has a different range than the original. I just hope that, if I ever have serious overheating, it will give proper notice.
I think I figured out what could be done about the "Power" indicator light. The "new" instrument cluster has a "4WD" light that is not being used. I should be able to figure out what lead was designed for the "Power" indicator and pull it from the connecter it is in and replace the "4WD" lead with that one. Then, when I put the ECT in Power mode, the 4WD light should come on. I probably won't take it apart again to do this, but if anybody does and it works, let me know!