98 Olds 88 LS Blower Motor Replacement

[HotZ28]

After further thought, I am not sure the blower uses a resistor for high-speed, only the three low-speeds. You may have a bad high-speed relay, or loose/burned wire somewhere!

[quickcurrent]

OK I've replaced the resistor, it was almost as hard to replace as the blower motor! It was also quite corroded. GM makes these things out of steel instead of copper or aluminum so rusting is a problem with them. The resistor has three coils, one for each of the lower speeds. I figure if the current does not pass through the resistor for the high speed the rust should not have affected it, but if it does, then that would explain why the fourth speed only worked sometimes - the rust was providing some resistance preventing enough current to pass through to run the fan at full throttle. So far so good, let's see if the problem is solved permanently. If not, it may be the relay as you say, HotZ28.

I've even put the underdash stuff all back on - gosh, I wish I was more flexible!

Thanks again,

QC

[quickcurrent]

My fan no longer works on any speed. It did at first, then it worked on high only, now nothing.

A few years ago I had some wiring repairs done in a repair garage and was charged four hours labor, three to diagnose and one to repair wires at a harness underneath the dash. Looks like I put the dash parts back too soon, LOL. I think it's the wires again now. I don't want to go and pay those dudes several hunderd dollars again for job that doesn't last. Any suggestions where to start looking for the lose/burnt wires?

[quickcurrent]

I took the relay box apart and put it back together as I could not see anything wrong with it. I opened up a couple of modules each with a fuse that I thought may have been the problem, for A/C and fan motor. Both fuses looked good so I pushed them back in and put everything back the way it was. Now the high speed works fine (at least so far!) but none of the other speeds still work! Could this be the relay? It seems to me that current is now getting through to the motor to run it at high speed (bypassing the resistor), but something is keeping the current from going through to the motor for the other three speeds. I've replaced the resistor twice. The first time I thought the resistor might have been faulty so I got a replacement and put that in, with the same results. So unless I got two faulty resistors both of which looked good to me (highly unlikely), something else is causing the problem. I just don't understand exactly what the function of the relay is. Can someone shed some light on this?

Thanks

[HotZ28]

The pic below may not be model specific, but it is a good indication of the manual fan control relay location and associated wiring/terminals. Have you looked at the wiring/terminal going to the resistor? These carry a lot of ampherage, especially when a motor is failing. A common problem with this set-up is; once the terminal and wires overheat, it will cause damage to both. When this happens, you will have to replace the terminal with new unit. They come from the dealer with the terminal and about 1-ft of wiring to splice into your existing wires after you cut the old terminal off. Have you changed the relays with another relay from the same area. All of them are the same, so you can just swap one from the horn or from some other function for testing purposes.

ACDelco Part # PT391

[quickcurrent]

Thanks.

I took apart the larger boxes above the small ones and they have fuses in them. Everything looked OK to me.

The smaller ones you show in the picture I just pulled out and looked at them and saw no wires burned or loose, so I just put them back where they were. I don't think they were marked as to what each one was for. I have not switched them as you suggest, but maybe I'll do that. The funny thing is it appears that something got modified just by pulling them out and putting them back because the high fan speed didn't work prior to that and it's working now - this suggests something is loose! I'll have to have a closer look. Maybe one of them is in fact damaged.

The terminal going to the resistor looked Ok too when I replaced the resistor. I may have to look at that again too, maybe I missed something there.

I have a multimeter. Is there a way to check for continuity at the various terminals?